Full Transcript: How to Prevent & Treat Colds & Flu
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0:00 - Welcome to the Huberman Lab Podcast,
0:02 where we discuss science and science-based tools
0:04 for everyday life.
0:09 I'm Andrew Huberman,
0:10 and I'm a professor of neurobiology and ophthalmology
0:13 at Stanford School of Medicine.
0:15 Today we are talking about the science of heat,
0:17 and more specifically the science of heating, the verb,
0:22 meaning how our body heats up
0:24 from both the outside and the inside.
0:27 Heat is a remarkable stimulus,
0:29 meaning when we are in a hot environment,
0:32 it has a profound effect on our biology.
0:35 And heating up from the outside,
0:38 or as you'll soon learn, from the inside,
0:41 has a profound effect on many different aspects
0:44 of our health, including our metabolism,
0:47 both in the immediate and long term;
0:50 our cognition, meaning our ability to think
0:52 more or less clearly.
0:54 And if you're immediately thinking that heating up
0:57 makes you less capable of thinking, you're wrong.
1:01 Heat applied properly as a stimulus
1:03 can engage certain neurochemical systems
1:06 in your brain and body
1:07 that can allow your brain to function far better.
1:10 We will talk about those data today.
1:12 So we're going to talk about
1:13 the science of heat and heating,
1:15 both in terms of their mechanisms.
1:17 And, as I know many of you are interested in,
1:19 the tools related to the use of heat,
1:21 things like sauna, how often to do sauna,
1:25 how long to be in the sauna,
1:26 how hot to be in the sauna
1:28 for particular goals and outcomes.
1:31 We're also going to talk about the very exciting new science
1:34 around local heating.
1:36 That is the use of heat applied
1:38 to specific areas of the body in order to heal
1:41 or improve tissues at that location that you are heating
1:44 as well as your biology and health overall.
1:47 In fact, we are going to talk about one
1:49 very recently published paper
1:51 that came out in the journal Cell.
1:53 Cell is one of the three apex journals,
1:55 meaning three of the most competitive,
1:57 most rigorous scientific journals.
2:00 Those are Nature, Science, and Cell.
2:02 This particular paper was published in Cell,
2:04 and I will go into it in more detail later,
2:06 but basically what this paper shows
2:08 is that by locally heating up skin and fat,
2:14 you can change the identity of certain fat cells
2:18 at that location and elsewhere.
2:20 We have three kinds of fat,
2:22 white fat, beige fat, and brown fat.
2:23 And as you will learn more about soon,
2:26 white fat is not very metabolically active.
2:28 It's more of a fuel reserve.
2:30 It's what we typically think of as blubbery fat.
2:33 Beige fat and brown fat are rich in mitochondria,
2:36 and those mitochondria provide a sort of furnace
2:39 or heating mechanism for your entire body
2:41 and increase your metabolism
2:42 and the burning of white fat.
2:45 So in other words,
2:46 having more beige fat and brown fat is a good thing.
2:49 And it turns out that the proper application
2:51 of heat to specific areas of your body
2:54 can increase the conversion of white fat to beige fat.
2:57 In other words, turn an innocuous fuel source
3:00 into a metabolically active tissue
3:03 that can help you burn off more white fat.
3:06 I think many people are going to be interested in this paper
3:09 and the tools that emerge from this paper.
3:11 It's a fascinating set of findings
3:13 that actually emerged from an understanding
3:15 of the biology of burn and people who receive intense burns.
3:20 And that is not what I'm going to recommend to you
3:21 as a tool, of course,
3:23 but understanding a little bit about how burns
3:26 impact our biology and health
3:28 has allowed these pioneering researchers
3:30 to develop new tools to combat
3:32 obesity and metabolic disorders,
3:34 and that you can apply for basic things like fat loss.
3:37 I'm pleased to announce that the Huberman Lab Podcast
3:40 is now partnered with Momentous Supplements.
3:42 Our motivation for partnering with Momentous
3:45 is to provide people one location
3:47 where they can go to access the highest quality supplements
3:50 in the specific dosages that are best supported
3:53 by the scientific research
3:55 and that are discussed during various episodes
3:57 of the Huberman Lab Podcast.
3:59 If you go to livemomentous.com/huberman,
4:02 you'll see those formulations.
4:04 I should mention that we are going to add more formulations
4:06 in the months to come,
4:08 and you'll see specific suggestions
4:10 about how best to take those supplements,
4:12 meaning what dosages and times of day,
4:14 and in fact, how to combine those supplements
4:17 with specific behavioral protocols
4:19 that have been discussed on the podcast
4:21 and are science supported
4:22 in order to drive the maximum benefit
4:25 from those supplements.
4:26 And many of you will probably also be pleased to learn
4:29 that Momentous ships not just within the United States,
4:32 but also internationally.
4:34 So once again, if you go to live momentus.com/huberman,
4:37 you will find what we firmly believe to be
4:40 the best quality supplements
4:42 in the precise dosages and the best protocols
4:46 for taking those supplements,
4:48 along with the ideal behavioral protocols
4:50 to combine with those supplement formulations.
4:52 I'm pleased to announce
4:53 that I am hosting two live events in May 2022.
4:57 The first live event will take place
4:58 in Seattle, Washington on May 17th.
5:01 The second live event will take place
5:02 in Portland, Oregon on May 18th.
5:05 Both are part of a lecture series entitled
5:07 The Brain Body Contract,
5:08 during which I will talk about science
5:10 and science-based tools,
5:11 many of which overlap with the topics
5:13 covered on the Huberman Lab Podcast,
5:15 but most of which will not
5:17 and will be completely new topics and tools
5:19 never discussed publicly before.
5:21 Both live events will also include
5:23 a question and answer period,
5:24 during which you, the audience,
5:26 can ask me questions directly
5:28 about any aspect of science or science-based tools,
5:30 and I will attempt to answer them.
5:32 Tickets for the two events, again,
5:34 Seattle on May 17th and Portland on May 18th,
5:38 are both available at hubermanlab.com/tour.
5:42 Before we begin, I'd like to emphasize that this podcast
5:45 is separate from my teaching and research roles at Stanford.
5:47 It is however part of my desire and effort
5:49 to bring zero cost to consumer information
5:51 about science and science-related tools
5:53 to the general public.
5:55 In keeping with that theme,
5:56 I'd like to thank the sponsors of today's podcast.
5:58 Our first sponsor is LMNT.
6:00 LMNT is an electrolyte drink
6:02 that has everything you need
6:03 and none of what you don't need, meaning sugar.
6:07 It has electrolytes, and the main electrolytes
6:09 are sodium, potassium, and magnesium,
6:11 which you need in the proper ratios
6:13 in order for your brain and body to function correctly.
6:16 LMNT was designed to get you the proper ratio
6:18 of electrolytes in order to optimize
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6:23 People out there with pre-hypertension and hypertension,
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6:28 But many people can actually benefit
6:30 from increasing their sodium intake,
6:32 both for health and for performance.
6:35 LMNT contains a science-backed electrolyte ratio
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6:44 I consume LMNT when I first wake up in the morning,
6:46 during exercise, and after exercise,
6:49 and sometimes again, if I've been sweating profusely,
6:51 for instance, after doing a sauna
6:53 or taking a run on a hot day, things of that sort.
6:56 If you'd like to try LMNT,
6:57 you can go to drinklmnt, that's lmnt.com/huberman
7:02 to claim a free LMNT sample pack.
7:03 You only cover the cost of shipping.
7:05 Again, that's drinklmnt, lmnt.com/huberman
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7:10 Today's episode is also brought to us by InsideTracker.
7:13 InsideTracker is a personalized nutrition platform
7:16 that analyzes data from your blood and DNA
7:19 to help you better understand your body
7:20 and help you reach your health goals.
7:22 I've long been a believer in getting regular blood work done
7:25 for the simple reason that many of the factors
7:27 that impact your immediate and longterm health
7:30 can only be analyzed from a quality blood test.
7:33 There are a lot of blood and DNA tests out there,
7:35 but a major issue with many of them
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8:08 So it not only gives you information
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8:11 it gives you directives as to how to improve your health.
8:14 If you'd like to try InsideTracker,
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8:25 Today's episode is also brought to us by ROKA.
8:28 ROKA makes eyeglasses and sunglasses
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8:33 I've spent a lifetime studying the visual system,
8:35 and I can tell you that your visual system
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8:39 It allows you to do things like
8:41 move from a shady area outside to a sunny area outside
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8:48 A lot of sunglasses and eyeglasses are not designed
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9:32 Okay, let's talk about heat,
9:34 more specifically, let's talk about
9:35 the biology of heat and heating
9:37 and the health benefits and tools
9:39 related to heat and heating.
9:42 The first question that we have to answer
9:44 is how do we heat up?
9:46 And the answer to that question is we heat up two ways.
9:50 We heat up from the outside,
9:53 meaning the things that we come into contact with,
9:55 the clothing that we put on our body,
9:57 whether or not there's heat in the room,
9:59 or whether or not it's cold outside or cold in a room,
10:02 and we heat up from the inside.
10:05 Our body has the capacity to generate more heat
10:09 or to cool down, meaning to turn off the heating process,
10:12 and it can do that in ways
10:15 that match the external environment.
10:18 The simplest way to think about this
10:20 is that we actually have two body temperatures.
10:23 People will say, "Oh, what's body temperature?
10:24 "98.6."
10:25 That's actually not true.
10:27 Body temperature varies between individuals.
10:29 It varies across time of day within individuals.
10:32 And at every point across your entire lifespan,
10:36 you have two distinct temperatures.
10:37 One is the temperature on your skin,
10:39 what scientists call your shell,
10:42 and the temperature of your core,
10:45 your viscera, meaning your organs,
10:47 your nervous system, and your spinal cord.
10:49 And as you can imagine,
10:50 the temperature of your core
10:52 is always higher than the temperature at your surface.
10:56 So the important thing to know
10:57 is that you have a temperature at your shell
10:59 and a temperature at your core.
11:01 Now you don't need to know exactly
11:02 what those temperatures are in most cases,
11:04 but it is vitally important to understand
11:07 that you have those two temperatures
11:08 and that your brain is constantly
11:10 sending out signals to your body
11:12 as to whether or not it should heat up or cool down,
11:16 depending on the temperature of the shell,
11:19 which makes total sense.
11:21 This is a lot like a thermostat in a room,
11:23 which is essentially paying attention
11:25 to how cold or hot it is,
11:27 and then sending signals to the heating or cooling system
11:29 to either heat up the environment
11:31 or cool down the environment,
11:32 depending on the temperature in that environment.
11:35 Your brain has neurons that send signals
11:38 to other cells in your body
11:40 and deploy the release of chemicals in your brain and body
11:43 to heat you up when you are too cold
11:45 and to cool you down when you are too hot.
11:48 So, if you can understand
11:50 that you have two body temperatures,
11:51 one at your shell, the surface,
11:53 and one at your core, inside,
11:55 and that your body and brain are always trying
11:57 to balance those two temperatures in the appropriate way,
12:00 well then you're halfway there
12:01 to understanding the biology
12:03 of thermal regulation and heating,
12:05 and you'll be a lot further along
12:07 in understanding how specific tools can be used
12:10 to improve metabolism or improve cognition, for instance.
12:14 In fact, later you will learn
12:17 that one way that you can heat up
12:19 is by cooling down the surface of your body.
12:21 That's right.
12:22 If I were to throw a cold towel, ice cold towel,
12:25 onto your torso right now and ask you,
12:28 "Well, how do you feel?"
12:28 You'd say, "Oh, that's cold, that's chilly."
12:30 However, because your brain is acting like
12:33 a bit of a thermostat as the surface,
12:35 the shell of your body felt cool,
12:37 it would make sense that that thermostat
12:39 would activate biological mechanisms
12:41 that would heat up your core.
12:43 Similarly, if I were to put you into a very hot environment,
12:47 you'd say, "Oh, wow, it's really, really warm in here,"
12:50 but your brain and your body would go
12:51 through a lot of effort to activate mechanisms
12:54 to cool you down.
12:55 So anytime we're talking about heat,
12:57 meaning deliberate heat exposure, things like sauna,
13:00 it's very important to understand, not just the stimulus,
13:03 how hot something is, how long you're in a sauna, et cetera,
13:06 but the effect that has on your shell and on your core.
13:10 If you can understand that you can design protocols
13:13 that are literally perfect for your goals.
13:15 And as a final point about this,
13:17 if you want to develop the best tools,
13:20 leveraging heat for your biology and health and performance,
13:23 you want to understand heat as a process,
13:26 as a verb, as heating, not just heat,
13:30 because there's the temperature that you are at
13:33 before you encounter the heat stimulus,
13:35 before you get in the sauna, for instance,
13:37 during the heat stimulus, so while you're in the sauna,
13:40 and then afterward.
13:42 Everything in biology is a process.
13:44 So as you'll soon learn,
13:45 there is a specific sauna protocol that can allow you,
13:49 can allow anybody, in fact,
13:50 to increase the amount of growth hormone
13:52 released into their brain and body 16 fold.
13:55 That's right, 16 fold.
13:57 However, it involves shifting from a hot environment
14:02 to a cool environment, to a hot environment,
14:04 to a cool environment, over and over and over again,
14:06 over a very short period of time,
14:08 because it engages a switch, a process,
14:11 that compounds, it builds on itself,
14:13 to increase growth hormone further and further.
14:15 In fact, if you were to just get into a sauna
14:17 for a very long period of time and crank up the temperature
14:21 to match the exact temperature that was used in that study,
14:24 you would not experience those increases in growth hormone.
14:27 It really is the transition
14:29 between hot and cool temperatures
14:31 that engage the process of heating
14:33 and reheating over and over again.
14:35 So, today you're going to learn about the use of sauna.
14:37 You're going to learn about the use of other heat-related tools
14:40 for health and optimization,
14:42 not just for growth hormone,
14:43 but also metabolic health, for controlling cortisol,
14:45 even to impact mental health in positive ways.
14:49 And in order to do that,
14:51 you need to understand a little bit about the mechanisms
14:54 of how you heat up and how you cool down,
14:57 where the cells and circuits are in the brain and body,
14:59 how those cells and circuits work.
15:01 I promise to make the description of that
15:02 which follows very clear,
15:04 even if you don't have a background in biology.
15:06 And once you have that in hand,
15:08 along with the understanding you now have
15:11 about the fact that you got a shell and a core,
15:13 and you need to think about both the shell and the core,
15:15 well, then you will be in the best possible position
15:18 to use sauna or hot tub or other tools,
15:21 even just a hot shower,
15:22 as a powerful stimulus to optimize your biology.
15:25 Now, the science of heat and heating
15:27 and cold and cooling, for that matter,
15:30 goes back well over a hundred years.
15:32 In fact, it's kind of amusing to me
15:33 that nowadays there's a kind of renewed interest
15:36 in the use of heat and cold
15:37 and the science of heat and cold,
15:39 because this was the first topic that I studied
15:41 as an undergraduate.
15:43 And in fact, I did my graduate thesis on thermal regulation.
15:46 And at the time, thermal regulation wasn't really considered
15:49 one of the hot topics in neuroscience.
15:52 People were more focused on things
15:53 like memory and consciousness.
15:55 And of course those topics are still of vital interest
15:57 to many people in many laboratories,
15:59 but thermal regulation was considered
16:01 more a thing for the physiologists.
16:04 Nowadays, not just on social media,
16:06 not just in the landscape of biohackers and athletes,
16:09 but in the landscape of mental health, and frankly,
16:12 in the general ethos around health optimization,
16:17 people are really interested in heat and cold.
16:19 And the reason they're so interested in heat and cold
16:22 is that a lot of the science has been done
16:24 both in animal models in mice and in humans
16:26 and translates immediately to protocols that anyone can use.
16:30 Now, a brief warning now and another brief warning later,
16:35 anytime you're talking about heating up your body,
16:38 you need to be very cautious,
16:39 because unlike cooling down,
16:41 where you have a fairly broad range of cold temperatures
16:44 that you can go into before it's damaging to tissue,
16:47 well, you don't get to heat up the brain and body very much
16:50 before you start getting into the realm of neuron damage,
16:53 and neuron's in the central nervous system,
16:55 the brain and spinal cord,
16:56 once they're damaged they don't come back.
16:58 So hyperthermia is a serious thing to avoid.
17:01 Later I'll talk about ways
17:02 to rapidly protect against hyperthermia,
17:06 but I do want to give everybody a cautionary note up front.
17:09 Obviously, if you're pregnant, nursing,
17:11 if you're very sensitive to hot environments,
17:13 you want to stay out of saunas and things of that sort.
17:15 I'm sure there are exceptions to that.
17:17 You definitely have to talk to your doctor
17:19 if you're going to violate that rule.
17:22 And for everybody, you want to approach
17:25 any kind of tool related to heating very cautiously.
17:28 You always have the opportunity
17:30 to increase the temperature later.
17:31 So proceed with caution.
17:32 Be smart about it.
17:33 I don't just say of that to protect me.
17:34 I say that also to protect you.
17:37 So now let's talk about
17:38 what are the circuits for heating up?
17:40 How does that happen?
17:42 Many of you have probably experienced a fever.
17:44 How does that happen?
17:45 What happens when you go into a cold environment
17:48 and you're shivering,
17:50 but you put on a coat and then you feel warmer.
17:51 What's really going on there?
17:53 Well, there's a very basic circuit,
17:56 meaning neurons that exist in the skin,
17:59 in the brain, and in the body
18:01 that communicate with one another that allow you
18:04 to heat up if you need to and cool down if you need to.
18:06 I'm going to throw a little bit of nomenclature,
18:08 a few new words at you.
18:10 You don't need to memorize these words, except for one,
18:13 actually you need to memorize one acronym,
18:15 but it's very easy.
18:16 It's called the POA.
18:18 If you remember POA,
18:19 you'll be home free for the rest of the episode,
18:21 but I know that there are some aficionados out there
18:23 and people interested in getting
18:25 a little bit deeper mechanism.
18:26 And I do think it's important to understand the circuit,
18:28 because once you stand this circuit
18:29 and the way it's structured,
18:31 then you are going to be in a great position to use the tools
18:34 related to heating.
18:35 So here's how this circuit is structured.
18:37 You have this shell, which is basically skin,
18:40 and within the skin you have neurons, nerve cells.
18:43 Those nerve cells have channels or receptors on them.
18:47 They're called trip channels.
18:48 There's some other ones as well,
18:50 which basically sense changes in heat.
18:53 So if I were to put a hot object on your hand or your arm,
18:57 or for instance,
18:58 if I were to put a hot object on your hand or arm,
19:00 and then remove that hot object,
19:03 those neurons would respond to that.
19:05 They would send electrical signals into your spinal cord.
19:07 And that's where the next station of the circuit resides.
19:10 In your spinal cord you got a little cluster of neurons
19:13 that exists at the top part of your spinal cord
19:16 called the dorsal horn.
19:18 The name, again, doesn't matter.
19:19 And those neurons specifically relay heat information
19:22 up to another area of your brain.
19:24 Now here's where we get into some fancy names.
19:26 It's the lateral parabrachial area.
19:29 You don't need to know lateral parabrachial area,
19:31 but it's a relay station.
19:32 The lateral parabrachial area
19:34 sends electrical signals to the POA.
19:37 And I would like you to know POA.
19:39 The POA stands for preoptic area.
19:41 Neurons in the preoptic area
19:43 basically reside over the roof of your mouth.
19:45 These are neurons within the hypothalamus,
19:48 and neurons in the preoptic area
19:51 have the ability to send signals
19:54 out to the rest of your brain and body
19:56 to get you to heat up and actually to change your behavior
20:00 so that you heat up.
20:02 That's right.
20:03 If neurons in the preoptic area
20:05 receive an electrical signal
20:07 through the circuit I just described,
20:08 that goes from skin to dorsal horn of the spinal cord,
20:11 to lateral parabrachial,
20:14 they will start sending signals
20:16 out to the organs of your body and the tissues of your body
20:19 to get those organs and tissues to do things.
20:21 And believe it or not, your POA, your preoptic area,
20:24 will actually change the way
20:25 that you think and feel immediately.
20:28 For instance, if something warm contacts your skin,
20:33 or something very hot contacts your skin,
20:36 the preoptic area will send signals
20:38 out to the endothelial cells,
20:42 the blood vessels both of the brain and body
20:45 that get them to dilate,
20:47 to essentially increase their volume and their surface area
20:51 in order to cast off heat.
20:54 You will also start sweating.
20:56 That sweating response is initiated,
20:58 not by the hot day or the hot sun,
21:01 but by the preoptic area neurons
21:03 that send signals out to what's called
21:05 the periphery of your
21:07 and other chemicals are released,
21:08 things like acetylcholine, that get you to sweat.
21:12 And if you happen to be shivering,
21:15 neurons in the preoptic area
21:17 will make sure that you stop shivering.
21:21 You're probably familiar with the feeling
21:23 of being somewhat lethargic,
21:24 or spreading out your limbs on a hot day.
21:27 Well, that is the result of neurons in your preoptic area
21:31 impacting your musculature
21:33 to get you to increase your surface area
21:36 so you can sweat off or release more heat.
21:39 So there are all these different mechanisms
21:40 by which we dump heat.
21:43 Some of those are purely physiological,
21:46 below our conscious control,
21:48 things like sweating,
21:49 which you can't just make yourself sweat on demand.
21:53 Maybe you can through a set of stressful thoughts,
21:55 but you can't just make yourself sweat.
21:57 That is autonomic, it's below your conscious control.
22:01 Things like vasodilation,
22:02 the dilation of your veins in particular
22:06 and capillaries in particular.
22:08 These sorts of things.
22:09 And, of course, there are these behavioral,
22:11 somewhat voluntary aspects of dumping heat.
22:15 And the lethargy, the kind of tiredness that we feel
22:17 on a really hot day,
22:19 that's also controlled by the circuit
22:21 that I just described.
22:22 In fact, I just got back from a visit to a very warm place,
22:26 and it was remarkable to me how lethargic I felt
22:29 in the afternoons.
22:30 I just felt like a total slug.
22:32 I just could not move or rally to do anything,
22:36 except if I waited until the evening,
22:39 even though it was later in the day,
22:41 even though I hadn't napped,
22:43 as the temperature in my environment cooled off,
22:45 as my body temperature cooled off,
22:46 I felt like I had more energy.
22:47 I was actually waking up,
22:48 even though I had been awake for longer.
22:50 So the relationship between temperature and lethargy
22:53 is a very intimate one.
22:55 If we're warm enough, we feel active
22:58 and like we want to move around.
22:59 If we're too warm,
23:00 we feel like we need to stay put
23:02 and spread out our limbs and dump heat.
23:05 And that brings me to a quick and kind of fun point
23:07 about how we dump heat versus how other animals dump heat.
23:10 Many of you know, of course, that we dump heat by sweating.
23:14 Other mechanisms as well, some of which I described,
23:16 but that's our main way of dumping heat.
23:19 Other animals like dogs don't have the capacity to sweat,
23:22 at least not very much,
23:23 so they pant in order to dump heat.
23:26 And still other animals, like rodents,
23:29 when they get too hot they spit on their paws
23:32 and they rub that spit on the surface of their body,
23:35 which might sound kind of gross,
23:36 and probably will get you to think twice
23:37 before petting any of those animals
23:38 or holding any of those animals again,
23:40 unless that's your thing.
23:42 Now, one other key thing to understand
23:44 about this circuit related to heat
23:46 is that the preoptic area
23:47 also can send electrical signals to the amygdala,
23:51 a brain area that is often talked about
23:53 in the context of fear,
23:55 but is really just a brain area
23:57 that can activate your sympathetic nervous system.
24:00 The sympathetic nervous system
24:01 is part of your autonomic nervous system
24:04 and is the one associated with fight or flight,
24:06 or with the stress response,
24:08 or even just the excited response.
24:10 The sympathetic nervous system is also what gets activated
24:12 when you're really excited about something.
24:14 The preoptic area has the opportunity
24:17 to trigger the activation of the amygdala.
24:19 Now, it doesn't do it every time, but it can.
24:22 And it tends to do that when you are suddenly
24:24 in an environment that feels too hot,
24:26 that you feel is risky levels of hot.
24:30 If you ever have gotten into a sauna
24:32 that was very, very hot, maybe 210 degrees Fahrenheit,
24:35 you sit there for a minute.
24:37 You'll notice that your heart rate increases,
24:39 and there are reasons for that,
24:40 and we'll talk about some of the health benefits of that
24:42 in a few minutes, but it's pretty uncomfortable.
24:45 You may not feel like your skin is going to burn up,
24:48 but you often will feel the impulse to get out,
24:51 especially if you stay in there for a little while.
24:53 That impulse is the consequence of this preoptic area
24:57 communicating with your amygdala saying,
24:59 "Hey, this environment is really hot,
25:01 and I'm tryin' to cool down,
25:02 and it's not really working.
25:03 I'm dumping heat, but I'm not able to adjust
25:06 the core of my body temperature
25:07 in ways that are going to protect my neurons.
25:09 And so it's a signal that you probably
25:11 shouldn't stay in that environment too long.
25:13 Now later we'll talk about the advantage
25:15 of pushing yourself a little bit through
25:17 some of these very hot environments,
25:18 provided you can do it safely,
25:20 but the impulse to get yourself
25:22 out of a very hot environment
25:24 is the consequence of the POA
25:26 communicating with your amygdala,
25:28 and the amygdala then, in turn,
25:30 activating your adrenal glands,
25:31 which sit right above your kidneys,
25:33 the release of adrenaline,
25:34 and this feeling of agitation like you want to move.
25:37 Usually you want to move out of whatever hot environment
25:40 you happen to be in.
25:41 So now you know the circuit.
25:42 Again, it's simple.
25:43 It goes from skin to spinal cord,
25:45 one brain area to another brain area.
25:47 That's the key one in this discussion,
25:49 which is the POA, the preoptic area.
25:51 And then the preop area can kick off
25:53 a bunch of autonomic subconscious responses to heat,
25:57 which make us attempt to get cooler,
26:00 things like sweating, vasodilation, et cetera,
26:02 and it can kick off behavioral responses,
26:05 spreading out our limbs in an attempt
26:06 to dump even more heat;
26:08 feeling lethargic, so a lack of desire to run and move;
26:12 and it also has the opportunity to kick off
26:14 a mild, or maybe not so mild,
26:16 panic response to get us out of that hot environment.
26:19 If you can conceptualize that circuit,
26:21 or if you can even just understand what I just said,
26:23 even at a top contour level,
26:25 you're going to be in a great position
26:27 to understand the rest of the information
26:28 and the tools that follow.
26:30 Next, I'd like to talk about the use
26:32 of deliberate heat exposure, including sauna,
26:35 but other tools as well,
26:37 as a way to understand how heat
26:39 and heating changes our biology.
26:42 So, you're going to learn some mechanism
26:44 and you're going to learn some tools.
26:46 But first I'd like to just emphasize
26:48 that the use of deliberate heat exposure
26:50 can be a very powerful way to improve health and longevity.
26:55 There's a wonderful study on this
26:56 that was published in 2018 that includes
26:59 a lot of data from a lot of participants,
27:02 in a lot of different conditions,
27:04 for instance, people that only did sauna once
27:06 versus two to three times a week
27:07 versus four to seven times a week and so on,
27:09 and compares all those.
27:11 The title of the study is Sauna Bathing is Associated
27:14 With Reduced Cardiovascular Mortality
27:16 and Improves Risk Prediction in Men and Women
27:19 a Prospective Cohort Study.
27:22 This is one of several papers that clearly demonstrate
27:26 that regular use of sauna or other forms
27:29 of deliberate heat exposure
27:31 can reduce mortality to cardiovascular events,
27:34 but also to other events,
27:35 things like stroke and other things
27:38 that basically can kill us.
27:40 What I like so much about this and the related studies,
27:43 and yes, I will provide a link to these in the show notes,
27:46 is that they involve a lot of participants.
27:48 So for instance, in this particular paper,
27:50 which was published in BMC Medicine,
27:53 they looked at a sample of 1,688 participants
27:58 who had a mean age of 63,
28:00 but there was a range of ages around 63,
28:03 and of whom 51.4% were women.
28:06 The rest were men.
28:07 So it's a pretty nicely varied study
28:09 in terms of the populations that they looked at.
28:12 And basically what they found
28:13 was the more often that people do sauna,
28:17 the better their health is
28:19 and the lower the likelihood they will die
28:22 from some sort of cardiovascular event.
28:24 What do we mean by sauna?
28:25 We need to define some of the parameters around sauna,
28:28 and I promise to provide you some alternative ways
28:32 to access some of the health benefits
28:34 that were observed in this and related studies
28:36 without the need to have a sauna,
28:38 'cause I do realize that a lot of people
28:40 don't have access to sauna.
28:42 First off, the temperature ranges that were used
28:44 in this and pretty much all the studies
28:46 that I'm going to talk about,
28:47 unless I say otherwise, are between 80 degrees Celsius,
28:51 meaning 176 degrees Fahrenheit,
28:54 and 100 degrees Celsius,
28:57 meaning 212 degrees Fahrenheit.
29:00 So somewhere in that range.
29:02 How hot should you make the sauna or the environment
29:05 that you get into should you decide to use these tools?
29:07 Well, that will depend on your tolerance for heat,
29:11 how heat adapted you are.
29:13 Yes, some people are better at sweating than others.
29:15 And over time we all get better at sweating.
29:17 Meaning if you go into the sauna more frequently,
29:19 you become a better sweater, not sweater you wear,
29:22 but the verb sweater,
29:24 you get better at sweating,
29:25 at dumping heat through the loss of water.
29:27 So it's going to depend.
29:29 I recommend starting on the lower end
29:32 of the temperature scale,
29:33 and if that's too hot for you
29:34 that you even lower the temperature further.
29:36 Now, how long were people exposing themselves
29:39 to these hot environments?
29:41 Anywhere from five to 20 minutes per session.
29:45 And as you'll soon learn,
29:46 very brief periods of just five minutes of heat exposure
29:49 can be a powerful stimulus
29:51 if the heat exposure is significantly great enough for you.
29:58 20 minutes can also be beneficial,
30:00 but 80 to 100 degrees Celsius,
30:03 meaning 176 degrees Fahrenheit to 212 degrees Fahrenheit
30:07 is the general range that this and most studies use.
30:10 In this particular study,
30:12 they compared the effects of people
30:14 that did sauna once a week,
30:16 two or three times per week,
30:18 or four to seven times per week.
30:20 And what they saw was really remarkable.
30:22 What they observed was that people
30:23 who went into the sauna two or three times per week
30:27 were 27% less likely to die of a cardiovascular event
30:31 than people that went into the sauna just once a week,
30:33 again at the temperature levels
30:36 and the duration that I talked about earlier.
30:38 And as you can imagine, the duration,
30:39 the temperature levels were related.
30:42 So if people went into very hot environments
30:45 that were really uncomfortable for them,
30:46 maybe they only went in for five minutes.
30:47 Whereas, if they were more comfortable and heat adapted
30:50 in a given environment or their tolerance for heat
30:53 was just simply higher for whatever reason,
30:55 well then they tended to stay in longer.
30:57 We can take a sort of average
30:58 of this five to 20 minute range,
31:00 and today we're mainly going to talk about exposures
31:03 between 10 and 20 minutes at temperatures between,
31:07 again, 80 degrees and 100 degrees Celsius,
31:09 176 degrees Fahrenheit, or 212 degrees Fahrenheit.
31:13 So these data point to the fact that going in the sauna
31:15 two or three times per week is really beneficial
31:17 and can lower mortality to cardiovascular events.
31:20 And in fact, the benefits were even greater
31:22 for people that we're going into the sauna
31:23 four to seven times per week.
31:25 Those people were 50% less likely to die
31:28 of a cardiovascular event
31:29 compared to people that went into the sauna
31:31 just once a week.
31:33 So these are really impressive, and frankly,
31:35 encouraging studies.
31:37 Certainly they caught my eye and encouraged me
31:39 to start using deliberate heat exposure on a regular basis.
31:43 What's particularly nice about this study,
31:45 and the related study that, again,
31:47 is linked in the show notes,
31:49 is that they looked at a number
31:51 of potentially confounding variables,
31:53 things like whether or not people smoked,
31:55 things like whether or not people were overweight,
31:57 whether or not they tended to exercise or not exercise,
32:00 and they were able to separate out those variables.
32:03 So the percentages that I described earlier,
32:05 27% less likely to die of a cardiovascular event
32:09 for those that went in the sauna two to three times a week
32:11 and 50% less likely to die of a cardiovascular event
32:13 for those that went into the sauna four times per week,
32:16 as compared to just once a week.
32:17 Those effects really do seem to be
32:19 the consequence of the sauna exposure
32:22 and not some other effect
32:24 that's correlated with sauna exposure,
32:25 like going to the gym where people
32:28 are working out seven times a week
32:29 and then also happen to get into the sauna,
32:31 or quitting smoking right about the same time
32:33 they adopt a sauna protocol, these sorts of things.
32:36 And now there have been additional analyses
32:38 of the use of sauna for improving health,
32:40 or I should say for offsetting mortality,
32:43 that have found that it's not just reductions
32:46 in cardiovascular events,
32:47 but so called all-cause mortality.
32:50 This is kind of medical geek speak for saying,
32:53 how likely are you or somebody to die
32:56 from a cardiovascular event,
32:58 but maybe be also from some other event,
33:00 some other health-related event,
33:02 like cancer or something of that sort.
33:04 And in every case,
33:05 regular exposure to sauna starting
33:07 at about two or three times per week,
33:09 all the way up to seven times per week,
33:12 greatly improves,
33:13 meaning statistically significant improvements in longevity
33:18 in the sense that people are less likely
33:20 to die of cardiovascular events
33:23 and other things that kill us.
33:25 So I and many other people
33:26 who are interested not just in our own health,
33:28 but in educating about health-related tools
33:31 to the general public, find this really exciting.
33:34 But knowing what we know about how heat impacts our biology,
33:39 it probably shouldn't surprise us
33:41 that this sauna type exposure
33:43 or deliberate heat exposure has these incredible effects.
33:46 So before we get into the biological mechanisms
33:49 of how heat can have all these impressive health effects,
33:52 I want to just talk about the use of sauna as a tool
33:56 and emphasize that you don't have to use a sauna
34:00 in order to get these benefits.
34:02 It is simply a matter of making sure that your shell
34:05 and your core heat up properly a bit,
34:10 not too much, not too little,
34:12 but that you heat those up.
34:13 And no, you do not need to carry a thermometer around
34:16 or place a thermometer into your core.
34:18 In laboratory studies and in humans,
34:22 if you really want to know someone's core temperature,
34:24 basically you try and put the thermal probe
34:25 as close to the core as you can.
34:26 So typically that's done rectally or a mouth thermometer
34:30 or even up the nose.
34:31 You don't need to do any of that.
34:32 This isn't a laboratory study.
34:34 There are ways to create a hot environment
34:37 such that you heat up your shell and your core safely
34:41 without having to measure your core temperature all along.
34:45 If you want to do that, be my guess,
34:46 but I'm not going to provide a protocol.
34:49 So the question is, how are you heating up your environment?
34:51 And I realize that there are dry saunas,
34:54 there are steam saunas, there are infrared saunas,
34:57 there are hot tubs,
34:59 and there are simply rooms that you crank up the heat.
35:04 There are also ways in which you can
35:05 increase your shell and your core temperature
35:08 by moving around a lot
35:09 and doing that wearing a lot of clothing.
35:12 There's nothing special about
35:14 any one of these approaches or protocols.
35:17 It just so happens that sauna
35:19 is one of the more convenient ways to do this.
35:21 And certainly for the studies that I've talked about,
35:24 not just the ones I referenced before,
35:25 but all the studies that I researched
35:27 looking at this episode,
35:29 it makes sense why they would use sauna,
35:30 because it's very hard, for instance,
35:32 to create conditions where you have
35:35 five people go out jogging,
35:37 wearing heavy sweaters and hats,
35:39 wool hats on the middle of summer,
35:41 it's very hard to set up those conditions
35:42 in a way that's controlled for everybody.
35:44 Whereas, it's pretty straightforward
35:45 to have a sauna where you have
35:47 one or several people just get into
35:48 that one uniformly hot environment.
35:51 That's a much easier study to run.
35:53 So just to be clear, the temperature range is important.
35:58 You want to get between 80 and 100 degrees Celsius.
36:00 Now you know the conversion to Fahrenheit.
36:03 You could, however, immerse yourself
36:06 in a hot tub or hot water bath up to your neck.
36:08 That's another way to approach it.
36:10 If you didn't have access to either of those,
36:12 you could also put on a hoodie or a wool hat and a hoodie,
36:19 or you could do like the wrestlers do,
36:21 and you could actually buy one of these plastic suits.
36:24 They're literally called plastics
36:25 that wrestlers or other athletes
36:27 that wish to drop water weight will wear,
36:29 and then go jogging in that.
36:30 All of those will increase your shell
36:31 and your core body temperature.
36:33 Especially if you do it on a hot day,
36:34 but of course be careful, hydrate and don't overheat.
36:36 Don't become excessively hyperthermic,
36:38 'cause you can get heat stroke and you can potentially die.
36:41 But if you're going to use sauna,
36:44 often I get the question how hot should the sauna be?
36:47 Well now you know.
36:48 How long should you be in there?
36:48 Five to 20 minutes per session.
36:51 Although, I will talk in a minute about ways
36:53 to optimize hormone output,
36:54 in particular growth hormone output,
36:56 by doing four very brief sessions.
36:59 So maybe not a continuous session.
37:01 We'll get into that in a few minutes.
37:02 And, of course, you have to ask yourself
37:03 wet sauna, dry sauna.
37:05 You know what?
37:05 Doesn't matter.
37:06 Use what you prefer.
37:08 Many people ask me, "Well, what about infrared sauna?"
37:10 We have an entire episode all about the use of light
37:13 and low level light therapy, including infrared light.
37:17 It does have certain benefits for skin
37:19 and other organs and tissues of the body, if used properly.
37:23 My understanding, or at least my assessment,
37:26 of most infrared saunas out there
37:28 is that they don't get hot enough.
37:30 They don't get up to that 80 to 100 degrees Celsius range.
37:34 Some do, most don't.
37:36 So what you end up with is a situation
37:38 where you've got a red light,
37:39 low level light therapy stimulus,
37:42 and you've got a sauna that's not quite hot enough.
37:44 And there are a lot of ideas and claims
37:46 about how they work together
37:48 in order to get you improved benefits.
37:51 I personally am of the stance,
37:53 based on the literature that I've read,
37:54 that you want to get into those ranges
37:57 of 80 to 100 degrees Celsius
37:59 before you start considering whether or not
38:02 you're also going to include red light therapies, et cetera.
38:04 So there's nothing special about red light sauna.
38:07 It's really the temperature of the sauna
38:10 that you happen to get into.
38:11 So which tool?
38:12 Which sauna?
38:13 Which stimulus?
38:14 Do you run wearing plastics and a hoodie and a wool hat
38:17 or do you get into a sauna?
38:18 That's going to depend a lot on your circumstances,
38:20 your budget, and what you have access to on a regular basis.
38:22 This is a lot like our discussion about the use of cold.
38:26 Most of the studies have looked at immersion in cold water
38:29 up to the neck,
38:30 because that's a very controlled situation
38:32 that you can do in a laboratory.
38:33 They have not explored cold showers as much,
38:36 So there's just less data,
38:37 or walking around in a cold environment.
38:39 But we'll talk a little bit about those data,
38:41 because as you'll soon learn, when you talk about cold,
38:44 you're actually talking about heating as well.
38:46 So what kind of mechanisms are activated
38:48 in your brain and body
38:49 that allow for the various health benefits
38:52 of sauna or other forms of deliberate heating?
38:56 Well, we talked about reduced risk
39:00 of cardiovascular event related mortality
39:02 and all-cause mortality.
39:04 As you'll soon learn,
39:05 there are also tremendous benefits
39:07 in terms of increases in growth hormone,
39:10 reductions in cortisol, et cetera.
39:12 I will detail those.
39:13 So what happens when you do get into a hot environment?
39:16 What are the mechanisms
39:17 that allow for the various health effects of that?
39:20 Well, your shell, your skin, senses that.
39:25 And through the circuit that I described earlier,
39:27 activates neurons in the POA, the preoptic area,
39:30 which in turn activates mechanisms
39:32 in your autonomic nervous system, like vasodilation.
39:35 So blood flow increases.
39:36 Plasma volume of your blood increases,
39:39 and stroke volume.
39:41 The volume of blood that is mobilized
39:44 with each beat of your heart also increases.
39:47 And your heart rate increases
39:49 to anywhere between 100 to 150 beats per minute.
39:53 That general constellation of effects
39:55 looks a lot like cardiovascular exercise.
39:58 And in fact, for all intents and purposes,
40:01 it really is cardiovascular exercise,
40:03 except that there isn't the mobilization
40:06 and the loading of joints and limbs and things of that sort.
40:09 And of course there are additional benefits
40:11 of cardiovascular exercise
40:13 that relate to impact on the ground,
40:16 improvements in bone density, et cetera, et cetera.
40:18 But basically your heart starts beating,
40:20 more blood starts circulating,
40:22 your vasculature changes shape, literally,
40:25 to accommodate those increases
40:26 in heart rate and blood volume.
40:29 And you're basically getting a cardiovascular workout
40:32 in that hot environment, even if you're just sitting down.
40:35 Another set of positive effects
40:36 related to being in these hot environments
40:40 are hormone effects,
40:42 shifts in the output of hormones,
40:44 both from or your adrenals
40:45 and possibly from the testes and ovaries
40:48 and even within the brain.
40:49 One of the more striking examples of that
40:52 comes from a study that was published in 2021.
40:56 The title of the study is
40:58 "Endocrine Effects of Repeated Hot Thermal Stress
41:00 "and Cold Water Immersion in Young Adult Men."
41:03 And indeed, this study was, in this case, just done on men.
41:06 I'll just briefly describe the protocol they used.
41:08 They had these men attend four sauna sessions
41:11 of 12 minutes each.
41:13 So again, well within that range of five to 20 minutes,
41:15 12 minutes.
41:17 The temperature of those saunas
41:18 was 90 to 91 degrees Celsius.
41:21 So I'll just quickly do the calculation,
41:23 admittedly, not in my head.
41:25 That's 194 degrees Fahrenheit, and they did that four times.
41:30 Afterwards they had a six-minute cool down break
41:33 during which they did get into some cool water
41:36 or cold water of about 10 degrees, which is,
41:39 10 degrees Celsius is 50 degrees Fahrenheit.
41:43 And then they measured hormones at various times
41:46 throughout this study, before, during, and after.
41:48 They looked at testosterone,
41:50 they looked at DHEA, which is in the androgen pathway.
41:54 They looked at prolactin and they looked at cortisol.
41:57 The significant effects of the protocol
41:59 that I just described were on cortisol,
42:02 a so-called stress hormone.
42:04 So-called because when we are very stressed
42:06 for long periods of time,
42:07 cortisol levels tend to increase dramatically.
42:09 But I should point out that a increase in cortisol each day
42:14 right about the time of waking,
42:15 and specifically right about the time of waking,
42:17 is actually beneficial for our alertness and our energy.
42:19 So having some increasing cortisol every 24 hours
42:23 is a good thing, provided it happens early in the day.
42:26 Late day increases in cortisol
42:28 are associated with depression.
42:30 That's been shown by studies at Stanford and elsewhere.
42:33 The major effect of this study
42:34 is a significant decrease in cortisol output
42:37 in these subjects.
42:40 I think this is really interesting and important,
42:41 because many people suffer from acute,
42:44 meaning immediate, and longterm stress,
42:46 and are looking for ways to control their stress.
42:49 Controlling your cortisol is tricky.
42:51 In the episode on stress,
42:52 I talked about supplements such ashwagandha
42:54 that can be used to limit cortisol,
42:56 but you have to be careful not to use ashwagandha
42:59 for extended periods of time,
43:00 meaning for longer than two weeks,
43:02 because you can get into other issues.
43:04 I talk about breath work protocols
43:06 that can allow you to clamp or reduce
43:08 the stress response in real time.
43:10 Again, see that episode for those,
43:11 but many people are overworked.
43:13 They're overstressed.
43:14 They're, for one reason or another,
43:16 they're subjected to many too many stressors
43:19 or their level of stress resilience isn't high enough
43:22 to keep their cortisol levels clamped at a healthy level.
43:25 So the protocol I described of 12 minute exposures
43:29 to 90 degree environment,
43:30 that's again, 90 degree Celsius,
43:33 followed by a six-minute cool down break
43:36 in cool water, 50 degrees or so, that's pretty cold.
43:39 I can imagine that you could also just take a cool shower
43:42 or a cold shower afterwards,
43:44 that had a very significant effect on lowering cortisol.
43:47 So there you have a tool
43:48 that's not a completely zero cost tool,
43:50 'cause you need to heat the water
43:51 and you need to have access to hot and cold water,
43:53 at least hot and cold contrast of some sort,
43:55 but it's fairly minimal cost for most people.
43:59 Especially if you start getting creative
44:00 about maybe taking a 12-minute jog
44:03 wearing a lot of clothing if it's hot out,
44:05 then getting into a cool shower.
44:06 You might not get the same extreme
44:08 or significant reduction in cortisol
44:10 that was observed here with these very specific protocols,
44:13 but it's likely that you would get
44:14 a similar result over all.
44:17 Now, I mentioned they did look at these other hormones,
44:18 and I'll just tell you
44:20 that they did not see significant shifts in testosterone,
44:22 prolactin, DHEA, et cetera, using this protocol.
44:26 As you'll soon see, there are other sauna protocols
44:28 that can impact those other hormones.
44:30 So if you're seeking to use sauna to reduce stress,
44:32 I think this is a very interesting
44:34 and potentially useful research-backed protocol.
44:37 And again, we will provide a link to the paper
44:39 if you'd like to read more about the data.
44:42 So that is one set of biological effects on cortisol
44:45 and the related protocol.
44:48 What about some of the other benefits of sauna?
44:50 Well, we'll talk about those,
44:51 but I want to talk about those in the context
44:54 of the underlying mechanisms,
44:56 because if you understand those underlying mechanisms,
44:58 you can really tailor your sauna protocols
45:00 for your particular needs.
45:02 One of the more dramatic and important effects
45:04 of going into a hot environment for some period of time
45:08 is the activation of so-called heat shock proteins, or HSPs.
45:13 Heat shock proteins are a protective mechanism
45:15 in your brain and body to rescue proteins
45:19 that would otherwise misfold.
45:21 What do I mean by this?
45:22 Well, most of you're familiar with the fact that
45:25 if you have protein in the kitchen,
45:27 like a steak or a piece of chicken or a piece of fish,
45:29 and you heat it up, it changes it's texture.
45:33 Raw meat is different than cooked meat,
45:35 to be quite blunt about it.
45:39 Heat changes the quality of proteins,
45:42 not just in terms of how they taste,
45:43 but the way in which they are configured.
45:46 It changes it right down at the molecular level.
45:49 When your body goes through changes in temperature each day,
45:53 and we'll talk about those changes,
45:54 but in response to hot environments or cold environments,
45:57 heat shock proteins are deployed to go and rescue
46:01 and prevent the changes in proteins
46:04 that would be detrimental to your health.
46:06 So at least in the short term,
46:08 activating heat shock proteins is a good thing.
46:11 You don't want heat shock proteins
46:12 to be activated for long periods of time,
46:14 because that gets to be problematic for other reasons.
46:17 But these heat shock proteins,
46:18 of which there are many varieties,
46:20 basically have the job of traveling in your brain and body
46:23 and making sure that cells
46:25 that contain proteins that are misfolding
46:28 because they got heated up too much, don't misfold,
46:32 and they also, sort of a protective mechanism,
46:35 making sure that proteins within the cells
46:37 of your brain and body don't fold in the wrong ways.
46:41 Again, I'm describing this in very general terms,
46:43 but it's well established in animal models and in humans,
46:47 that sauna exposure of the sort that I described earlier
46:50 activates these heat shock proteins.
46:52 There's some interesting studies that were carried out
46:54 in animal models that really nicely
46:57 mechanistically support the role of heat shock proteins
47:01 in some of the benefits of deliberate heat exposure.
47:04 Some of these studies were done in flies,
47:06 meaning Drosophila, fruit flies,
47:08 'cause there are great model organism,
47:10 because you can delete genes or add genes easily.
47:13 Other studies have been done in mice.
47:14 And now there are also studies being carried out in humans,
47:17 and I will talk about those.
47:18 One of the more dramatic examples
47:20 that's always touted in this field
47:22 of deliberate heat exposure as it relates to longevity
47:25 is that if they expose these flies, these fruit flies
47:29 to 70 minutes of a heat stimulus that would,
47:34 obviously didn't kill them,
47:35 but activated heat shock proteins,
47:37 it could extend their life by 15%
47:40 in a heat shock dependent way.
47:42 Meaning if they made flies
47:44 that didn't have these heat shock proteins,
47:47 well then they didn't see this extension in life.
47:50 And this is one of the reasons to use model organisms.
47:52 This is not an experiment that you could do in people.
47:54 However, there have been interesting studies done in humans,
47:57 examining some of the downstream molecular pathways
48:00 of deliberate heat exposure
48:02 that point to the mechanisms
48:03 by which deliberate heat exposure
48:05 can help protect against different forms of mortality,
48:08 improve overall, and possibly,
48:11 and I want to highlight possibly,
48:12 possibly extend life.
48:15 One such mechanism involves a genetic program
48:18 involving a molecule called FOXO3.
48:22 FOXO3 is a very interesting molecule,
48:24 because it's involved in DNA repair pathways.
48:28 DNA repair is part of the process of remaining healthy.
48:32 We'd all like to think that we're born,
48:34 and based on the genes we have,
48:36 we are healthy, healthy, healthy,
48:38 then eventually we age and then we die.
48:40 But from the time we're born, until the time we die,
48:44 there's a constant repair of our proteins in our cells
48:47 in a modification of the genes that are being expressed,
48:50 puberty being the most dramatic example.
48:52 You see a kid before puberty and after puberty,
48:54 looks like a different kid,
48:55 sounds like a different kid, thinks like a different kid.
48:56 In fact, it basically is a different human being.
48:59 It's not just the hormones.
49:00 It's that hormones themselves have the capacity
49:02 to turn on and turn off certain genes,
49:05 literally converting certain tissues and cells
49:08 in the brain and body to do entirely different things.
49:10 So it's not just the sprouting
49:12 of new aspects of our biology.
49:15 It's literally the conversion of different brain centers
49:17 from one function to another.
49:21 That's puberty.
49:22 And we'll do a whole episode about puberty.
49:24 We actually did an episode on sexual development
49:26 that talks a little bit about those mechanisms.
49:28 But the point is that throughout our entire lifespan,
49:31 genes are being turned on, genes are being turned off.
49:33 Genes are being turned on.
49:34 Gene are being turned off.
49:35 And DNA, the stuff of genes, gets damaged in that process.
49:41 FOXO3 sits upstream in a pathway related to DNA repair,
49:47 and again, clearing of the senescent cells.
49:50 Sauna exposure,
49:52 in particular sauna exposure two to three times
49:55 or ideally four to seven times per week
49:57 in that 80 to 100 degree Celsius range
50:01 has been shown to upregulate levels of FOXO3.
50:05 FOXO3 in turn upregulates pathways related to DNA repair
50:10 and clearing out of these senescent or dead cells,
50:12 which is known to be important
50:14 for various aspects of maintaining cognition
50:17 and other aspects of maintaining health.
50:20 So these are the likely biological mechanisms
50:23 for the improvements in lifespan,
50:27 or rather, I should say,
50:29 these are the biological mechanisms
50:30 that apparently offset some of the cardiovascular risk
50:35 and other forms of mortality that were described earlier.
50:38 One especially interesting thing about FOXO3,
50:42 there are individuals out there
50:44 that have either additional copies of FOXO3
50:47 or who have versions of FOXO3 that are hyperactive,
50:52 so to speak,
50:53 those people tend to be 2.7 times more likely
50:58 to live to 100 years of age or longer.
51:01 So these are people that were just naturally,
51:03 and fortunately for them, endowed with more FOXO3,
51:06 more clearance of senescent cells,
51:08 more DNA repair, et cetera.
51:10 For the rest of us, at least to my knowledge,
51:13 I don't have one of these health-promoting FOXO3 mutations.
51:17 Remember, mutations can be beneficial
51:19 or they can be detrimental.
51:20 This, if your goal is to live longer,
51:23 is a beneficial mutation.
51:25 If you don't have these FOXO3 mutations
51:27 that allow you to be a centenarian
51:29 at 2.7 times high or likelihood than other people,
51:33 deliberate heat exposure is one way
51:35 that you can increase FOXO3 activity.
51:38 At this point in time,
51:39 meaning when looking at the research out there,
51:42 it isn't clear what the optimal sauna protocol
51:45 is going to be, specifically to increase FOXO3,
51:48 and that's probably because there isn't one.
51:50 There is no sauna protocol
51:52 designed specifically to reduce cortisol
51:55 or specifically to increase FOXO3
51:58 or specifically to activate heat shock proteins.
52:01 Any deliberate heat exposure
52:03 is likely to impact all of those mechanisms.
52:06 Again, I encourage you to use this guide
52:07 of 80 to 100 degrees Celsius
52:10 as your kind of bookends for what you can tolerate
52:14 and where you want to start and eventually transition to
52:18 in terms of deliberate heat exposure.
52:19 And I would encourage you to use
52:22 that five to 20 minutes per session for the sauna
52:26 as your rough guide of how long to remain in this sauna.
52:29 Now, there was a study published just this last year
52:32 that was mainly focused on deliberate cold exposure.
52:34 I detailed this quite extensively in the episode on cold.
52:39 This is the beautiful work of Susanna Søberg.
52:41 And that study looked at deliberate cold exposure,
52:43 but also sauna exposure.
52:45 And that study found that 57,
52:49 yes, 57 minutes per week of sauna exposure
52:53 in conjunction with 11 minutes per week total
52:57 of deliberate cold exposure
53:00 was the threshold for getting improvements
53:03 in metabolism and increases in brown fat,
53:06 this very active fat tissue
53:08 that improves mitochondrial function and thermogenesis,
53:12 meaning heating of the body.
53:13 We'll talk more about brown fat later.
53:14 Why do I mention this?
53:15 Well, for those of you that are interested
53:17 in increasing metabolism,
53:19 it does seem to be most beneficial
53:21 to do that 11 minutes per week of cold exposure, again,
53:25 divided up across two or more sessions.
53:27 So it's not 11 minutes all at once,
53:28 but shorter sessions,
53:29 and to get 57 minutes minimum per week
53:33 of sauna exposure, again,
53:35 in the temperature ranges that I've talked about here.
53:37 And again, it's not 57 minutes in the sauna all at once.
53:42 That's 57 minutes total per week as the minimum threshold.
53:46 So you might divide that into three sessions of 20 minutes.
53:49 And again, I don't think 57 is the magic number.
53:53 It could be 60, it could be 64.
53:55 It probably could be 55.
53:57 Remember your biological systems
53:59 are not counting things off minute by minute,
54:00 second by second, least not in most cases.
54:02 So for those of you that are interested
54:04 in improving metabolism, check out the episode on cold,
54:07 or just take the Søberg Protocol, as I call it,
54:11 which is 11 minutes total per week of uncomfortably cold,
54:15 but safe, cold exposure.
54:16 So uncomfortably cold means
54:18 you really, really want to get out of the shower
54:20 or the ice bath or whatever environment,
54:22 but you can stay in,
54:23 11 minutes total per week divided across a couple sessions
54:25 and then 57 minutes per week, or so,
54:29 of deliberate heat exposure,
54:32 again, uncomfortably,
54:33 but uncomfortably hot, excuse me,
54:35 but safe to stay in,
54:37 probably divided up across three or more sessions.
54:39 Okay, so we've talked about the use of sauna
54:41 to decrease cortisol.
54:43 We've talked about the use of sauna
54:44 to increase heat shock proteins.
54:47 We've talked about the use of sauna
54:48 to increase FOXO3.
54:51 Now I'd like to talk about the use of sauna
54:53 to increase growth hormone.
54:55 Growth hormone is a hormone
54:57 that we all naturally secrete from our pituitary,
54:59 which also resides near the roof of our mouth.
55:02 The signal for the pituitary to release growth hormone
55:06 arrives from neurons that exist in the hypothalamus.
55:10 So growth hormone releasing hormones,
55:13 believe it or not, that's what they're called,
55:14 stimulate the release of growth hormone
55:17 from the anterior pituitary gland
55:19 into the general circulation,
55:21 and then growth hormone impacts metabolism and growth
55:25 of cells and tissues of the body.
55:27 It is responsible for tissue repair as well.
55:30 And the growth spurt
55:31 that everyone experiences during puberty
55:33 is the consequence of growth hormone.
55:36 What I'm about to describe is a study
55:39 that found dramatic, really dramatic I should say,
55:43 increases in growth hormone,
55:45 but I also want to emphasize that these increases
55:47 in growth hormone were not of the sort
55:49 that are observed in puberty or in infants
55:51 becoming adolescents or adolescents growing into teenagers.
55:55 Those levels of growth hormone that are associated
55:57 with those massive transformations, excuse me,
56:00 of body morphology, of shape,
56:02 are far greater than the sorts that I'm talking about here.
56:06 And yet, as all of us age,
56:09 when we go from adolescence to our teenage years
56:13 and then into a young adulthood,
56:14 but then starting in our early 30s or so,
56:17 the amount of growth hormone that we secrete
56:19 is greatly diminished.
56:21 Normally we would release growth hormone every night,
56:24 after we go to sleep,
56:25 in particular in the early part of the night
56:27 when our sleep is comprised mostly of slow-wave sleep.
56:31 As we age, less growth hormone is released
56:34 during that slow wave sleep.
56:36 There are various things
56:37 that can promote the release of growth hormone,
56:39 and we will talk about some of those other things
56:42 in a moment, things like low blood sugar,
56:44 turns out, is a stimulus for growth hormone release.
56:50 And I don't mean hypoglycemia of the sort
56:52 that makes you dizzy and want to pass out.
56:54 That's bad.
56:55 I mean, not having high levels of glucose and insulin
56:57 in your bloodstream.
56:58 This is one of the reasons why many people
57:00 are drawn to intermittent fasting or even prolonged fasting,
57:04 it's because of the reported increases in growth hormone.
57:07 I'll touch on those briefly,
57:08 but if you want to learn more about those
57:10 and what their real impact is
57:13 and the extent of growth hormone,
57:14 check out the episode I did on fasting.
57:17 You can find that at hubermanlab.com.
57:19 Certain forms of exercise have also been shown
57:21 to stimulate growth hormone release.
57:23 And in a few moments,
57:24 I'll talk about how exercise and fasting can be combined
57:26 or how heat can be combined with exercise
57:30 or certain patterns of food intake
57:31 to further increase growth hormone.
57:32 But before I do that,
57:34 I want to review some of the data,
57:35 and one study in particular,
57:36 that discovered certain forms of deliberate heat exposure
57:40 using sauna can stimulate very large increases
57:44 in growth hormone output,
57:45 which for people in their 30s, 40s, and beyond
57:48 could be very useful,
57:49 and may also be useful for people
57:50 who are just trying to stimulate
57:52 the release of more growth hormone
57:53 in order to, for instance, recover from exercise
57:55 or stimulate fat loss or muscle growth or repair
57:58 of a particular injury.
58:00 The title of this paper
58:01 is "Endocrine Effects of Repeated Sauna Bathing."
58:04 And this is a paper that was published in 1986,
58:07 which is some years ago,
58:08 but nonetheless serves as a basis
58:11 for a lot of other studies that followed.
58:13 So let me describe what they did in this study.
58:16 They used an 80 degree Celsius environment,
58:18 so that's 176 degrees Fahrenheit,
58:21 and they had subjects do the sauna for 30 minutes,
58:25 four times per day.
58:27 So that's two hours total in one day,
58:30 30 minutes in the sauna, a period of cool down rest,
58:33 30 minutes in the sauna again,
58:34 cool down rest, a third, and a fourth time.
58:36 So, two hours total in this 80 degree Celsius environment.
58:41 So that's a lot,
58:42 but what they observed was really quite significant.
58:45 So they had subjects do this protocol,
58:47 and I should mention they had both male and female subjects
58:50 in this study,
58:51 and the entire study lasted a week.
58:53 They did this two hours of sauna exposure on day one,
58:56 day three, and day seven of that week.
58:59 And they measured a lot of different hormones,
59:02 cortisol, thyroid stimulating hormone,
59:05 thyroid hormone itself,
59:07 luteinizing hormone, and follicle stimulating hormone,
59:10 which are hormones that essentially drive
59:13 the production of other hormones.
59:15 We won't get into that too deeply,
59:16 but if you'd like to learn about FSH,
59:18 follicle stimulating hormone, and luteinizing hormone,
59:20 please see the episode on optimizing
59:22 testosterone and estrogen at hubermanlab.com.
59:25 They looked at prolactin and they looked at growth hormone.
59:28 I'll just cut to the chase
59:30 and tell you the effects on growth hormone.
59:33 In subjects that did this two hour a day,
59:36 80 degree Celsius protocol
59:38 experienced 16-fold increases in growth hormone.
59:43 So they measured growth hormone
59:44 before the sauna and after the sauna
59:47 and growth hormone levels went up 16 fold,
59:49 which is obviously an enormous,
59:52 and it turns out statistically significant, effect.
59:56 Now, one important caveat here.
59:59 Remember earlier when I talked about
1:00:02 people who did sauna once a week
1:00:04 versus two to three times a week
1:00:05 versus four to seven times a week,
1:00:07 and the more often people did sauna,
1:00:09 the less likely they were to die of cardiovascular events
1:00:12 or other things of that sort?
1:00:13 Well, in this case,
1:00:15 the effects of sauna exposure on growth hormone
1:00:18 actually went down the more often
1:00:21 that people did this deliberate heat exposure.
1:00:24 So as I mentioned,
1:00:25 they did this two hour a day
1:00:26 divided into 30 minute sessions protocol
1:00:28 on day one, day three, and day seven of a week.
1:00:33 And what they found was on day one,
1:00:35 there was a 16-fold increase in growth hormone.
1:00:38 On day three, however,
1:00:39 there was still a significant effect on growth hormone
1:00:42 as compared to before sauna,
1:00:44 but that effect was basically cut by two thirds.
1:00:49 So now instead of getting a 16-fold increase,
1:00:52 it was more like a three or four-fold increase,
1:00:54 which is still a huge increase,
1:00:56 but not as great as the increase observed on day one.
1:00:59 And then on day seven, there tended to be
1:01:02 a two, maybe a threefold increase,
1:01:04 but not as great as the one observed on day one.
1:01:09 What does this mean?
1:01:10 And why does this happen?
1:01:11 Well, the reason this happens is because heat,
1:01:15 just like cold, is a shock or a stressor to the system.
1:01:20 In the context of cold,
1:01:22 if you get into a very cold ice bath,
1:01:25 for instance, a five-degree ice bath, even for 20 seconds,
1:01:29 it's known to increase norepinephrine 200%.
1:01:33 It can double the amount of norepinephrine
1:01:35 that you suddenly release into your brain and body,
1:01:37 which actually can have some positive effects.
1:01:39 I'll talk about those in a little bit,
1:01:41 but if you were to do that every day,
1:01:43 you would become cold adapted.
1:01:45 This circuit that compares the shelling core of your body
1:01:50 would adjust in ways that it could either predict
1:01:53 that cold stimulus,
1:01:55 or more likely to create some thermogenetic mechanisms
1:01:58 in preparation for that cold exposure.
1:02:02 This is why, for instance,
1:02:03 people that use deliberate cold exposure
1:02:05 to try and increase lipolysis, the burning of fat,
1:02:08 oftentimes will get results for a while,
1:02:09 but then if they're doing it a lot, a lot,
1:02:11 they stop getting those effects.
1:02:13 I talk a lot about avoiding cold adaptation,
1:02:15 if that's your goal, in the episode on cold,
1:02:18 but similar mechanisms are at play here.
1:02:20 So we have to imagine that
1:02:22 when the subjects got into the sauna on day one,
1:02:24 whatever pathways went
1:02:25 from measurement of temperature at the shell
1:02:28 to changes in temperature at the core
1:02:30 led to these big increases in growth hormone,
1:02:32 which is basically a way of just describing the result
1:02:34 I already told you before.
1:02:36 But the fact that that result diminished over time
1:02:38 either means that the circuit was not as efficient
1:02:41 in communicating that shift in temperature
1:02:43 or that that shift in temperature was of less impact
1:02:46 because the downstream effectors
1:02:49 were not engaged to the same extent
1:02:51 because it wasn't as much of a shock.
1:02:52 And I think the latter explanation is far more likely.
1:02:55 This is very much akin to weight training
1:02:57 or cardiovascular exercise,
1:02:59 where if you run up a hill very fast, for instance,
1:03:01 and your lungs are burning
1:03:03 and you're heaving and breathing hard,
1:03:05 on the first day, that's a very painful thing.
1:03:07 But if you do it every day or every other day,
1:03:09 provided you allow yourself to recover,
1:03:11 pretty soon you're running up that hill
1:03:12 and you're not breathing as hard.
1:03:14 There isn't as much burning in your muscles,
1:03:16 et cetera, et cetera.
1:03:18 Your body adapts.
1:03:19 So, one of the key things to understand
1:03:21 about the use of deliberate heat exposure
1:03:23 is if you're going to use it
1:03:25 in order to try and trigger massive increases
1:03:27 in growth hormone,
1:03:28 you're going to need to be careful about
1:03:29 not doing it more than, let's say, once a week.
1:03:32 Now, I'm extrapolating from this study.
1:03:34 Maybe once every 10 days would be even better,
1:03:36 but if you start getting heat adapted,
1:03:39 it's very unlikely that you're going to get
1:03:42 these massive increases in growth hormone.
1:03:44 So I don't mean to be discouraging
1:03:45 of using deliberate heat exposure
1:03:47 to access growth hormone increases,
1:03:49 but if that's your specific goal or your main goal,
1:03:52 then I think it's reasonable to say
1:03:55 that you don't want to do deliberate heat exposure,
1:03:57 at least not of the sort that I described here,
1:03:59 more than once a week, or maybe even once every 10 days,
1:04:02 and that you would want to time that
1:04:03 to other events in your life, maybe hard workouts,
1:04:06 or if you are trying to push through a fat loss barrier
1:04:10 or simply in order to access growth hormone at peak levels,
1:04:14 maybe three times per month or four times per month.
1:04:17 If you start doing deliberate heat exposure more often,
1:04:19 you'll still get increases in growth hormone,
1:04:21 but they are not going to be nearly as large
1:04:24 as the increases in growth hormone
1:04:25 that you're going to experience if you shock your system
1:04:29 with deliberate heat exposure every once in a while.
1:04:32 An important way to frame this
1:04:34 is actually in the context of cold.
1:04:36 And while you might say, wait,
1:04:37 this is an episode on heat and heating, not cold,
1:04:39 you really can't have a conversation about heat and heating
1:04:42 without talking about cold.
1:04:43 Because, as I mentioned earlier,
1:04:45 if you cool the outside of your body, the shell,
1:04:48 you're actually heating up your body.
1:04:50 In fact, the circuits that control heating of the body
1:04:52 and that control cooling of the body,
1:04:55 for instance, the activation of things like shiver
1:04:57 or fat loss in response to cold and shiver,
1:04:59 those are also controlled by the preoptic area
1:05:02 of the hypothalamus.
1:05:03 So we can take a step back and start to think about
1:05:06 what it would take to design
1:05:08 the optimal protocol for deliberate heat exposure
1:05:12 by looking at cold,
1:05:13 and here's what I mean.
1:05:15 There have been beautiful studies
1:05:16 showing that if people get into a very cold body of water,
1:05:20 four degrees Celsius for 20 seconds.
1:05:22 As I mentioned earlier,
1:05:23 that will cause the a 200 to 300% increase
1:05:26 in norepinephrine.
1:05:28 Norepinephrine is also called noradrenaline.
1:05:30 And norepinephrine and other so-called catacholamines
1:05:33 like dopamine increased dramatically
1:05:35 in this very brief cold water exposure.
1:05:37 And those increases in norepinephrine and dopamine
1:05:40 are known to have long-lasting effects
1:05:42 that generally lead to improvements
1:05:44 in mood, focus, and alertness.
1:05:46 So they're pretty significant.
1:05:48 However, they aren't significant enough
1:05:50 to increase metabolism to a very high degree.
1:05:53 Whereas, other studies have shown
1:05:55 that if people go outside in 16 degree Celsius weather
1:05:59 with a proper amount,
1:06:01 but a fairly minimum amount of clothing,
1:06:03 you can experience even greater increases in norepinephrine.
1:06:07 But the time that's required in order
1:06:09 to experience those increases is six hours at,
1:06:13 for instance, 16 degrees Celsius.
1:06:15 So if you have six hours a day to be out there in the cold,
1:06:17 or if you can turn the air conditioning on
1:06:19 in an environment and make it very, very cold, fine.
1:06:21 But basically what I'm describing is that
1:06:22 you can sort of bookend the parameters that you can use.
1:06:25 You can use a very brief exposure to cold or to heat
1:06:29 in order to stimulate heat shock proteins,
1:06:31 growth hormone, et cetera,
1:06:32 or you can use longer exposure
1:06:34 in less intense versions of heat and cold.
1:06:38 You really have to find what's going to work for you
1:06:39 and what you can do safely.
1:06:41 And if you're confused about where to start,
1:06:44 please use the parameters that I described earlier.
1:06:46 First of all, check with your doctor.
1:06:48 As always, make sure that you're somebody
1:06:50 who can do deliberate cold or heat exposure safely,
1:06:52 but that 80 to 100 degrees Celsius,
1:06:55 meaning 176 degrees Fahrenheit to 212 degrees Fahrenheit,
1:06:58 that I keep repeating over and over,
1:06:59 'cause I know somebody's going to ask,
1:07:01 even though I repeat it over and over, which is fine,
1:07:03 I'm delighted to keep saying it,
1:07:05 and to respond if someone asks again.
1:07:07 Well, those parameters are going to kind of
1:07:09 bookend what you should do
1:07:10 in terms of the intensity of the heat stimulus.
1:07:13 How long?
1:07:14 Well, we heard earlier, five to 20 minutes.
1:07:16 Why not start with five and then ramp it up to 10 or 15?
1:07:19 And then if you're feeling really bold
1:07:21 and you really want to crank out growth hormone,
1:07:23 well, then you could do
1:07:24 that 30 minute four times in one day stimulus
1:07:26 every once in a while.
1:07:28 So you have to really figure out
1:07:29 what you're using heat exposure for.
1:07:31 This is one of the reasons why when people say,
1:07:34 is it better to get in a wet sauna or dry sauna?
1:07:36 What's the optimal temperature?
1:07:38 Is it better to take a hot shower
1:07:39 or a hot bath or a hot tub?
1:07:40 To be completely honest,
1:07:42 it depends on what you're going to be able to do regularly,
1:07:44 whether or not you want to do it regularly,
1:07:46 and what your specific goals are.
1:07:47 So the purpose of this episode
1:07:48 is really to arm you with the underlying mechanisms
1:07:51 and to arm you with the general parameters
1:07:52 that are going to allow you
1:07:53 to access the results that you're seeking.
1:07:55 For what it's worth, I personally use a protocol,
1:07:58 and I've been using a protocol for a long time,
1:08:00 that involves trying,
1:08:02 meaning I accomplish this most weeks, not all,
1:08:04 trying to get into a sauna
1:08:06 for three 20-minute sessions every week.
1:08:10 I use a dry sauna, so it's not a steam room.
1:08:12 If I don't have access to it,
1:08:14 I might take a hot bath or something of that sort.
1:08:16 But in general,
1:08:17 I just stick to doing the sauna three times a week.
1:08:19 And I generally will do that either after a workout,
1:08:23 either a cardiovascular workout or a weight workout,
1:08:26 or I will do it later in the evening.
1:08:28 Why later in the evening?
1:08:29 Well, it has to do with the circadian shifts in temperature
1:08:33 that we all experience.
1:08:34 Talked a lot about this in the circadian episodes
1:08:37 and the episodes related to sleep.
1:08:38 But in a nutshell, here's how it works.
1:08:42 Every early morning,
1:08:43 about two hours before your typical wake up time,
1:08:47 your body temperature is at its all-time lowest.
1:08:51 We call that your temperature minimum.
1:08:53 Right about waking your body temperature increases.
1:08:55 In fact, an increase in body temperature
1:08:56 is part of the reason you wake up at all,
1:08:59 unless, of course, you're setting an alarm.
1:09:02 Increases in body temperature
1:09:03 are going to be one of the major things
1:09:06 that wakes up your brain and body.
1:09:08 Body temperature will tend to continue
1:09:10 to increase through the morning.
1:09:11 You'll get that increase in cortisol.
1:09:13 That's a healthy increase in cortisol.
1:09:14 Body tempera will increase into the afternoon,
1:09:17 and then we'll start to drop in the later afternoon.
1:09:20 This general contour can be shifted
1:09:22 by whether or not you exercise, how often you eat,
1:09:24 because of the so-called thermogenetic effects of food.
1:09:27 That is, every time you eat there's a slight increase
1:09:29 in body temperature and metabolism,
1:09:30 but it's not really that significant
1:09:33 to throw off this general contour and rhythm,
1:09:35 but toward the afternoon around four or five o'clock,
1:09:38 most days, depending on time of year,
1:09:39 your body temperature will peak,
1:09:41 and then it will start to drop.
1:09:42 And as your body temperature drops by one to three degrees,
1:09:45 and here I'm referring to your core body temperature,
1:09:47 not your shell body temperature,
1:09:49 you will start to get sleepy
1:09:50 and to transition into sleep
1:09:52 and to maintain sleep throughout the night.
1:09:54 Your body temperature will remain low
1:09:57 until you hit that temperature minimum,
1:09:58 and then it'll start to come up again.
1:10:00 What that means is that when you decide
1:10:03 to do sauna, or cold exposure for that matter,
1:10:06 it's going to be important.
1:10:07 Why?
1:10:08 Well, as I mentioned earlier,
1:10:09 if you were to make the surface of your body cold,
1:10:11 at least in the immediate period after that,
1:10:14 your body temperature will increase.
1:10:16 So for those of you that are challenged in getting to sleep
1:10:20 and are still working on your sleep,
1:10:21 remember sleep is the foundation
1:10:23 of all mental and physical health and optimal performance,
1:10:25 you should try to get really quality sleep
1:10:28 of sufficient duration, at least 80% of nights.
1:10:30 That should be an ongoing goal throughout your lifespan
1:10:32 for a huge number of reasons.
1:10:35 Watch the master sleep episode
1:10:36 if you'd like to hear are more of those reasons
1:10:38 and the mechanisms to make sure that you do that.
1:10:40 But in any event,
1:10:42 cold exposure late in the evening
1:10:44 will start to increase your body temperature again.
1:10:48 And that can make it hard for some people to fall asleep.
1:10:50 Now, if you're very, very tired,
1:10:52 because you've been working hard or training hard
1:10:54 or both throughout the day,
1:10:55 might not throw off your sleep so much.
1:10:57 I've gone through bouts
1:10:58 where I'm just so, so busy from morning till night,
1:11:00 that the only time I can get into the ice bath
1:11:02 or the cold shower is late in the evening
1:11:03 and I have no trouble sleeping after that.
1:11:05 However, if you have trouble sleeping,
1:11:07 I would recommend doing the cold exposure early in the day
1:11:10 to match that natural heating,
1:11:12 that natural increase in body temperature
1:11:15 that occurs across the 24-hour so-called circadian rhythm.
1:11:19 Similarly, if you're going to use deliberate heat exposure,
1:11:24 you'd be wise to do that later in the day.
1:11:27 You'd be wise to do it later in the day
1:11:28 because when you get into a warm environment,
1:11:31 sure, the surface of your body, the shell, heats up,
1:11:34 the core of your body heats up,
1:11:36 but then it also activates cooling mechanisms
1:11:39 through the preoptic area,
1:11:41 and when you get out of that hot environment,
1:11:43 sauna or otherwise, your body will continue to cool down.
1:11:47 And so many people find that if they do sauna
1:11:49 in the later half of the day,
1:11:50 or even just before sleep
1:11:53 and then take a warmish shower afterwards,
1:11:55 then they find it easier to fall asleep.
1:11:57 And that makes sense
1:11:58 because their body temperature is dropping.
1:12:01 And in fact, if your goal is to really promote
1:12:03 the maximum amount of growth hormone release,
1:12:05 that's also going to be the best time of day to do it,
1:12:07 especially if you haven't eaten
1:12:08 in the two hours before sleep.
1:12:11 So if you're really going for growth hormone release,
1:12:13 you're really trying to optimize sleep,
1:12:15 and the two things are actually linked
1:12:16 because of the release of growth hormone
1:12:18 that happens from the pituitary in the early nights sleep,
1:12:21 well, then you would be wise to do your sauna
1:12:23 maybe once or maybe twice a week
1:12:25 in the evening or at nighttime,
1:12:28 then taking a warm or cool shower just briefly,
1:12:30 just enough to kind of rinse off all the sweat from the sauna,
1:12:33 and then get ready for sleep.
1:12:35 And to do that, not necessarily fasted,
1:12:38 but to try and keep your levels
1:12:39 of glucose and insulin somewhat low in your bloodstream.
1:12:42 The reason I say that is that having elevated blood glucose
1:12:46 and or insulin tends to blunt
1:12:49 or reduce growth hormone release,
1:12:51 and that's true for any number of different stimuli
1:12:54 including exercise and including sauna.
1:12:57 So there's a really nice study on this
1:12:59 that I can point you to,
1:13:00 is this study that was published in the journal Stress.
1:13:03 Literally, that's the name of the journal.
1:13:04 I love it when journals have these names
1:13:06 like Pain or Stress.
1:13:08 I find that somewhat amusing for reasons that escape me,
1:13:11 but nonetheless, amuse me.
1:13:13 The title of this study is "Growth Hormone Response
1:13:15 "to Different Consecutive Stress Stimuli in Healthy Men.
1:13:18 "Is There Any Difference?"
1:13:19 And I don't want to go into all the details of the study,
1:13:21 because it's pretty extensive and complicated,
1:13:23 but basically what they did is they had people
1:13:24 do sauna and then gave them a drug
1:13:28 or a condition of having low,
1:13:30 not dangerously low, but low blood sugar.
1:13:33 Or they had them in a condition
1:13:34 where they had low blood sugar and then did sauna.
1:13:37 Or they had them do an exercise protocol
1:13:39 that led them to increased growth hormone
1:13:42 and then had them do low blood sugar.
1:13:44 Basically mixing and matching the various stimuli
1:13:47 that could increase growth hormone.
1:13:49 And what they found was very straightforward.
1:13:51 What they found was that doing sauna once
1:13:54 and then waiting some period of time
1:13:56 and then later that day doing sauna again,
1:13:58 they didn't see the same increase
1:14:01 in growth hormone both times.
1:14:03 First they got a big increase in growth hormone
1:14:05 and then less if they did sauna again.
1:14:07 If they had people do exercise and then sauna,
1:14:09 what they found was exercise could stimulate growth hormone,
1:14:12 but then following it with sauna
1:14:14 did not allow you to get twice as much growth hormone.
1:14:18 In general, anytime you release growth hormone,
1:14:21 you reduce the likelihood
1:14:22 that you're going to release growth hormone again
1:14:25 later that day.
1:14:26 And this partially explains that earlier study,
1:14:28 where if people did this growth hormone promoting protocol
1:14:31 on day one, but then on day three
1:14:33 they didn't see quite as big an effect,
1:14:34 and on day seven they didn't see quite as big effect.
1:14:36 All it basically boils down to is that
1:14:38 if you really want to crank out
1:14:40 the most amount of growth hormone in response to sauna,
1:14:43 do it fasted or at least not having ingested any food
1:14:46 in the two or three hours before.
1:14:48 You don't have to be deep into a fast,
1:14:50 and the whole notion of what breaks a fast
1:14:52 is kind of an interesting conversation,
1:14:53 because it's contextual.
1:14:55 Will a sip of coffee break your fast?
1:14:57 Well, maybe probably not.
1:14:59 Will one grain of sugar break your fast?
1:15:01 No.
1:15:02 Will an entire candy bar break your fast?
1:15:05 Yes, it has to do with where your blood glucose is
1:15:07 when you ingest that particular food item.
1:15:09 Not so much what that food item, is per say.
1:15:12 But the bottom line here is if you want to crank out
1:15:14 the most amount of growth hormone,
1:15:15 wait a couple of hours after eating
1:15:17 before getting into the sauna,
1:15:18 or maybe do it before dinner and then prepare dinner...
1:15:21 Do the sauna before dinner, that is,
1:15:23 then prepare dinner, then eat dinner,
1:15:25 and then make sure that you wait a few hours
1:15:27 before going to sleep.
1:15:28 You're going to have to arrange your schedule accordingly.
1:15:31 I know most people can't arrange their schedule perfectly
1:15:34 just to get growth hormone increases,
1:15:35 nor do I think people should approach
1:15:37 health protocols that way.
1:15:38 I think for 90% of people 90% of the time,
1:15:42 just getting into the sauna once or twice
1:15:45 or three times a week is going to be beneficial
1:15:47 for the number of reasons that I described earlier.
1:15:50 And you don't want to obsess too much
1:15:52 about out the exact conditions you need
1:15:54 in order to get the greatest effect
1:15:55 out of that sauna treatment.
1:15:57 These are just some additional tweaks
1:15:58 related to food intake
1:15:59 and low level hypoglycemia and exercise,
1:16:03 that if you wanted to leverage, you could.
1:16:05 So if decreases in body temperature
1:16:06 tend to aid the transition of sleep
1:16:08 and getting out of a hot sauna
1:16:10 tends to promote decreases in body,
1:16:13 it makes sense why you would want to put
1:16:15 your sauna exposure or other deliberate heat exposure
1:16:18 in the second half of your day,
1:16:19 and maybe even right before sleep.
1:16:21 Now, regardless of what time of day you do sauna
1:16:24 or how frequently you do it,
1:16:25 you're going to want to hydrate after going in the sauna.
1:16:28 When you go in the sauna, you lose water,
1:16:31 and when you lose water,
1:16:33 you need to replace it.
1:16:34 Why?
1:16:34 Well, you need water for all your cells,
1:16:36 but you also need electrolytes.
1:16:37 So make sure that you're replacing the water
1:16:39 that you lose in the sauna.
1:16:41 Now there's no exact formula of how much water to drink
1:16:43 and whether or not you need electrolytes
1:16:45 in that water or not.
1:16:46 It's going to depend on how much you sweat,
1:16:48 meaning how heat adapted you are.
1:16:49 It's going to depend on how much salt
1:16:51 you tend to excrete in your sweat.
1:16:52 Huge amount of variation, but in general,
1:16:55 one way to approach this would be to make sure
1:16:57 that you drink at least 16 ounces of water
1:17:00 for every 10 minutes that you happen to be in the sauna.
1:17:04 You could do that before and during and after,
1:17:06 you could do it during and after, or you could do it after.
1:17:09 Now, there are other reasons to do deliberate heat exposure
1:17:12 that have nothing to do with cardiovascular effects,
1:17:15 nothing to do with growth hormone or anything of that sort,
1:17:18 but rather have to do with improvements
1:17:20 in mood and mental health.
1:17:21 In fact, the data related to sauna
1:17:25 and other forms of deliberate heat exposure
1:17:26 improving mood are very impressive,
1:17:29 both at the mechanistic level
1:17:31 and in terms of the longterm consequences
1:17:33 that people experience.
1:17:35 First of all, we need to ask,
1:17:36 how is it that deliberate heat exposure
1:17:38 can improve our mood and wellbeing?
1:17:40 Well, it turns out that it improves mood and wellbeing,
1:17:43 but it also improves our capacity to feel good
1:17:47 in response to things that
1:17:49 would ordinarily make us feel somewhat good.
1:17:51 Now, this is not a situation
1:17:53 where you're going to be walking around grinning ear to ear
1:17:56 in response to nothing at all,
1:17:58 simply because you went in a sauna.
1:18:00 What I'm talking about is the up regulation of pathways,
1:18:04 meaning chemical pathways in your brain and body
1:18:06 that allow you to experience pleasure in all its fullness.
1:18:10 So here's how this whole deliberate heat exposure,
1:18:12 sauna, mood thing works.
1:18:14 Many of you have probably heard of endorphins.
1:18:17 Endorphins are a category of molecules
1:18:19 that are made naturally in your brain and body
1:18:22 and that are released in response
1:18:23 to different forms of stressors.
1:18:26 That's right, in response to stressors.
1:18:28 So, if ever you've gone out on a long run,
1:18:30 and at some point in that run,
1:18:31 you feel like you're aching and your joints hurt,
1:18:33 or maybe you have shin splints, and you push through that,
1:18:37 part of the reason that you experience
1:18:39 a lack of pain at some point, usually,
1:18:42 or you experience a euphoria during or after that exercise
1:18:46 is the exercise-induced effects on endorphin release.
1:18:50 Or rather, to be more specific,
1:18:52 I should say the exercise-induced consequences
1:18:55 on the stress system,
1:18:56 which in turn trigger the release of endorphin.
1:18:59 In other words,
1:19:00 when we experience short term or acute stress,
1:19:04 the endorphin system is activated.
1:19:06 Now the endorphin system is not just about feeling good,
1:19:10 believe it or not.
1:19:10 It also about feeling bad.
1:19:12 And there are two general categories of endorphins.
1:19:15 The first are the ones that you normally hear about,
1:19:17 endorphins, things that bind for instance
1:19:19 to receptors like the mu opioid receptor.
1:19:22 Opioids are not just prescribed compounds
1:19:25 or unfortunately drugs of abuse,
1:19:28 which they are.
1:19:29 We have this opioid crisis
1:19:30 in the United States and elsewhere,
1:19:32 which is a very serious and tragic thing,
1:19:34 but we make endogenous opioids.
1:19:37 We make endorphins that naturally act as pain relievers
1:19:40 and that make us feel mildly euphoric.
1:19:43 We also make endorphins such as dynorphine,
1:19:47 that's D-Y-N-O-R-P-H-I-N-E, dynorphine,
1:19:52 that actually make us feel worse in response to stressors.
1:19:57 When we get into a hot sauna,
1:19:59 or a hot environment of any kind,
1:20:01 dynorphins are liberated in the brain and body.
1:20:04 And I should mention that dynorphins are made
1:20:06 by many neurons in many different areas of the brain.
1:20:10 So you might think, well, why would I want that?
1:20:12 Why would I want to release dynorphine into my brain and body?
1:20:15 Well, first of all,
1:20:15 when you get into an uncomfortably hot situation,
1:20:19 uncomfortably hot scenario, oh gosh,
1:20:21 this is sounding terrible.
1:20:22 And a deliberately hot environment
1:20:25 that you are using to try and trigger
1:20:27 some sort of biological or psychological benefit,
1:20:30 I should say,
1:20:32 the discomfort that you feel,
1:20:33 the desire to get out of that environment,
1:20:36 is in part the consequence of the release of dynorphine.
1:20:40 It's also the consequence
1:20:42 of the activation of that sympathetic nervous system.
1:20:43 Remember, the preoptic area can communicate
1:20:46 with the amygdala and trigger
1:20:47 that kind of fight or flight mode,
1:20:48 I want to get out of the sauna.
1:20:49 This is really, really hot.
1:20:51 But dynorphine is also liberated
1:20:53 from a certain number of neurons.
1:20:55 Dynorphine binds to what's called the CAPA receptor.
1:20:59 The CAPA receptor binds dynorphine
1:21:02 and triggers pathways in the brain and body
1:21:05 that lead to agitation, to stress,
1:21:07 and believe it or not to a general sense of pain.
1:21:10 This is why you want to get out of the hot sauna,
1:21:13 and remember if it's unsafe levels of hot,
1:21:15 then you should get out of that sauna
1:21:17 or other hot environment.
1:21:19 But if you're working in a range
1:21:21 or you're exposing yourself
1:21:22 to a range of heat that's uncomfortable,
1:21:23 but safe to be in, dynorphine will be liberated
1:21:27 from these neurons, bind to the CAPA receptor.
1:21:30 And as a downstream consequence of that,
1:21:33 there will be an increase in the receptors
1:21:35 that bind the other endorphins,
1:21:38 the endorphins that make you feel soothed,
1:21:40 that make you feel happy,
1:21:41 and that make you feel mild euphoria.
1:21:44 So there've been a number of studies showing
1:21:45 that initially deliberate heat exposure,
1:21:48 by sauna or otherwise,
1:21:49 causes the release of dynorphine.
1:21:51 In fact, I think it's fair to say
1:21:52 that every time we get
1:21:53 into a hot environment that's uncomfortable
1:21:55 or a cold environment that's uncomfortable,
1:21:57 dynorphine is likely released
1:21:59 and binding to the CAPA receptor.
1:22:02 But over time that binding of dynorphine
1:22:04 into the CAPA receptor leads to downstream changes
1:22:08 in the way that the feel good endorphins,
1:22:10 things like endorphin binding to the mu opioid receptor,
1:22:13 and there are still other feel good endorphins,
1:22:15 so to speak.
1:22:17 That system becomes much more efficient,
1:22:20 such that people feel an elevation
1:22:22 in their baseline level of mood,
1:22:24 and when a good or happy event comes along,
1:22:27 they feel a heightened level of happiness or joy
1:22:31 or awe or improved mood in response to that.
1:22:34 This is not unlike the effects of caffeine
1:22:36 on the dopamine receptor that I've described previously.
1:22:39 And for those of you that aren't familiar with it,
1:22:41 many of you drink caffeine and love it.
1:22:44 Part of the reason you love it
1:22:45 is because of the release of certain neurochemicals,
1:22:47 like norepinephrine, et cetera,
1:22:50 the energy that it gives you.
1:22:51 Maybe the taste, I would hope, as well,
1:22:53 but caffeine ingestion also causes increases
1:22:56 in dopamine receptor concentration and efficacy.
1:22:59 In other words, it allows the receptors for dopamine
1:23:01 to work better so that
1:23:03 for a given amount of dopamine release,
1:23:05 you experience more pleasure and motivation.
1:23:08 This is a similar mechanism,
1:23:10 but within the endorphin pathway.
1:23:11 So what does it mean?
1:23:12 It means that a little bit of discomfort
1:23:15 as a consequence of deliberate heat exposure,
1:23:17 while in the short term,
1:23:19 doesn't feel good, by definition,
1:23:21 it is activating pathways
1:23:22 that are allowing the feel molecules and neural circuitries
1:23:27 that exist in your brain and body
1:23:28 to increase their efficiency,
1:23:31 placing you in a better position to be joyful
1:23:33 in response to the events of life.
1:23:35 I confess I'm very excited about the data
1:23:37 on deliberate heat exposure
1:23:38 and improvements in the chemical systems
1:23:41 that underlie good mood.
1:23:44 And just to underscore this further,
1:23:46 the dynorphine system is not unique to heat-induced stress.
1:23:51 In fact, there are beautiful studies and reviews
1:23:54 out there about the role of dynorphine
1:23:56 in stress and depression,
1:23:58 in stress and alcoholism,
1:24:01 just as a brief aside,
1:24:02 and in the future we will do a whole episode
1:24:04 on alcohol and alcoholism,
1:24:07 but turns out that chronic alcohol use and alcoholism
1:24:10 causes changes in dopamine receptors
1:24:12 that make it very difficult for people
1:24:15 to achieve pleasure through things
1:24:17 other than alcohol, and even alcohol.
1:24:19 That's kind of the really diabolical nature of addiction,
1:24:22 which is the thing that initially brings pleasure,
1:24:24 eventually is just required
1:24:26 to maintain baseline levels of dopamine.
1:24:28 And I've talked before, and Dr. Anna Lembke,
1:24:31 when she was a guest on this podcast,
1:24:33 talked about the pleasure pain balance
1:24:36 that exists within the dopamine system.
1:24:38 It is beautifully described
1:24:39 in her book "Dopamine Nation," by the way.
1:24:41 Excellent book I recommend to all people, addicts or not.
1:24:45 Well, in that context of pleasure and pain
1:24:48 it's very clear what the pleasure molecule is.
1:24:51 It's actually a molecule more related to motivation,
1:24:53 and that's dopamine.
1:24:55 The pain molecule, however, appears to be dynorphine.
1:24:59 And the fact that dynorphine is dysregulated
1:25:03 in stress and depression and alcoholism
1:25:05 and the relationship between dynorphine and dopamine
1:25:07 is something that we should all take very seriously.
1:25:10 And for that reason,
1:25:11 I'm very excited about the fact
1:25:13 that deliberate heat exposure
1:25:14 can leverage the dynorphine system
1:25:17 in a short term and an acute way
1:25:19 that allows mood to improve after the sauna exposure.
1:25:23 So, for those of you that don't like heat exposure,
1:25:26 keep in mind that a lot of the observed positive effects
1:25:31 on our biology relate to metabolism,
1:25:33 cardiovascular function, but also mental health.
1:25:36 And along those lines, there is a wonderful study,
1:25:39 again, published in 2018.
1:25:42 I don't know why.
1:25:43 I guess 2018 was a big year
1:25:44 for deliberate heat exposure studies.
1:25:47 The title of this study is "Sauna Bathing
1:25:50 "and Risk of Psychotic Disorders."
1:25:52 And this was a prospective cohort study.
1:25:55 Again, we'll provide a link to this study.
1:25:57 It's a really interesting study
1:25:58 that explored the relationship between mental health,
1:26:01 so people suffering from various forms of psychoses,
1:26:04 schizophrenia and other forms of psychoses,
1:26:06 and use of sauna.
1:26:08 So essentially what this study did
1:26:09 is they looked at a very large number of subjects,
1:26:12 more than 2,000 subjects,
1:26:14 who had no history of psychotic disorders.
1:26:16 They were classified into three groups
1:26:17 based on their frequency of sauna use,
1:26:20 either once a week, two to three to times per week,
1:26:23 or four to seven times per week.
1:26:24 This should call to mind that earlier study
1:26:27 on all-risk mortality and cardiovascular event risk.
1:26:31 And then they explored the hazard ratio
1:26:35 for psychosis specifically,
1:26:37 meaning how likely it was that people
1:26:38 would develop psychotic symptoms
1:26:40 or full blown psychotic illness,
1:26:43 according to their frequency of sauna session.
1:26:46 So, again, this isn't causal, this is correlative.
1:26:48 And according to the data in this study,
1:26:50 what they concluded is that
1:26:52 there was a strong and inverse independent association
1:26:55 between frequent sauna bathing
1:26:56 and the future risk of psychotic disorders
1:26:58 in this population.
1:27:00 Now, this does not mean that going
1:27:03 into a sauna seven times per week
1:27:04 is going to prevent people
1:27:05 from becoming schizophrenic, necessarily,
1:27:08 or from having a psychotic episode, necessarily.
1:27:10 And of course, frequent sauna use will be
1:27:13 related to other health-promoting activities.
1:27:16 But in this study, as in the previous study,
1:27:19 they went to great lengths in order to try
1:27:21 and limit those so-called confounding variables.
1:27:24 Now, of course, this is just one study,
1:27:26 and again, it's correlative, not causal,
1:27:28 but based on the large number of subjects they included,
1:27:31 plus the rigor of the statistical analysis,
1:27:33 we're starting to see a general picture
1:27:36 that using the sorts of sauna protocols
1:27:38 that I've described throughout this episode,
1:27:41 five to 20 minutes or so,
1:27:44 done one to seven times per week
1:27:46 is associated with a general improvement
1:27:50 in cardiovascular health,
1:27:51 a general improvement in mental health,
1:27:54 and it really points to the fact that,
1:27:56 yes, sauna done acutely for three or four times a day,
1:28:01 30 minutes each session separated by cooling,
1:28:03 maybe getting into cold bath,
1:28:04 sure that can potently increase growth hormone,
1:28:08 but done on a more regular basis can reduce cortisol,
1:28:11 improve heart health, improve mental health.
1:28:13 And for that reason, and the fact that for most people,
1:28:17 it is conceivable to come up with a way
1:28:19 that you could get into deliberate heat exposure
1:28:21 for a minimum of cost.
1:28:22 If it's a hot bath, or if you had to resort to
1:28:26 bundling up and going for a jog, this sort of thing,
1:28:28 or if you have access to it, a sauna of some sort,
1:28:31 that we're really talking about a stimulus
1:28:34 to initiate a large number of different biological cascades
1:28:38 that wick out to improve multiple aspects
1:28:42 of brain and body health.
1:28:43 So up until now, I've been talking about whole body heating.
1:28:46 So for instance, putting your whole body into the sauna,
1:28:49 which of course is what most people do,
1:28:51 or getting into a hot tub or hot bath up to your neck,
1:28:55 or in the cases where we were talking
1:28:56 about deliberate cold exposure as a means
1:28:58 to increase core body temperature and metabolism,
1:29:01 getting into an ice bath or cold water of some sort
1:29:05 up to your neck or into a cold shower, et cetera.
1:29:08 Now I'd like to talk about deliberately heating or cooling
1:29:10 specific parts of the body,
1:29:13 meaning certain surface areas of your body
1:29:16 as a means to get effects on those particular areas,
1:29:19 as well as at the whole body level.
1:29:21 Numerous times throughout this episode,
1:29:23 I've talked about the dangers of overheating.
1:29:25 So what should you do if you think you or someone else
1:29:27 is hyperthermic, is too hot?
1:29:30 Well, if you understand just a little bit
1:29:32 about the cooling and heating systems
1:29:34 of your shell and core,
1:29:36 there are some terrific tools that you can use
1:29:38 in order to cool off your core quickly.
1:29:41 And remember the core consists of the nervous system,
1:29:43 the spinal cord, and the viscera,
1:29:44 which are really the organs you're trying to protect.
1:29:47 So, being able to cool off the core of your body quickly
1:29:50 can be very beneficial,
1:29:52 and in some cases, it could even save your life.
1:29:54 There is a way to more quickly heat or cool the body,
1:29:58 and that's through specific elements of your shell,
1:30:01 meaning particular skin surfaces.
1:30:03 I've talked extensively about this in the episode on cold.
1:30:06 It was also covered in the episode
1:30:09 with my guest, Dr. Craig Heller,
1:30:10 from the Biology Department at Stanford.
1:30:12 It relates to the so-called glabrous skin surfaces
1:30:16 on the upper half of our face,
1:30:18 palms of our hands, and the bottoms of our feet.
1:30:20 And for those of you that have heard this before
1:30:23 I encourage you to continue to listen nonetheless,
1:30:25 because today I'm going to talk about
1:30:26 specifically how to heat the body or cool the body
1:30:30 through these glabrous skin surfaces.
1:30:32 Very briefly, the mechanism is as follows.
1:30:35 The palms of our hands, the bottoms of our feet,
1:30:37 and the upper half of our face
1:30:39 overly specific types of vasculature,
1:30:42 meaning specific types of veins and arteries
1:30:46 that don't have capillaries between them,
1:30:48 and as a consequence,
1:30:50 heat and cold can move very quickly
1:30:54 from the palms of the hands, the bottoms of the feet,
1:30:57 and the upper half of our face,
1:30:58 and change our core body temperature.
1:31:01 There's a name for these particular vascular structures.
1:31:04 They're called AVAs or arteriovenous astemoses.
1:31:08 Basically veins and arteries interacting directly
1:31:12 without capillaries in between,
1:31:14 which allows cooling of blood or heating of blood
1:31:18 much more quickly than is possible
1:31:20 by applying colder heat elsewhere on the body,
1:31:23 where capillaries intervene between veins and arteries.
1:31:26 These AVAs, arteriovenous anastomoses,
1:31:28 can be leveraged to cool off
1:31:30 your core body temperature very quickly.
1:31:32 The key thing is to get the palms of your hands,
1:31:35 the bottoms of your feet, and the upper half of your face
1:31:37 in contact with a cold surface or fluid
1:31:40 that is cold enough to cool the blood
1:31:44 and the core of your body,
1:31:45 but not so cold that it constricts the veins
1:31:49 just below the palms of your hands,
1:31:51 the bottoms of your feet, or the upper half of your face.
1:31:54 So, not placing ice packs necessarily,
1:31:57 but maybe placing cool towels on the bottoms of feet,
1:32:00 the palms of the hands, and the upper half of the face,
1:32:02 and as they warm up, replacing those with other cool towels.
1:32:06 The exact temperature will depend
1:32:07 on how hot you happen to be.
1:32:08 I can't know that without
1:32:10 knowing your particular circumstances.
1:32:12 If you'd like to learn more about
1:32:13 how to cool off your core very quickly,
1:32:16 and some of the details and some of the technologies
1:32:18 that are being developed to do that,
1:32:20 please see the episode I did with Craig Heller
1:32:21 or the episode on cold.
1:32:23 If you don't want to go to those episodes,
1:32:25 here is a good procedure that you could use.
1:32:27 You could grab, for instance,
1:32:28 a package of frozen broccoli or frozen blueberries.
1:32:32 If someone is really, really warm,
1:32:33 make sure they take off their shoes and socks,
1:32:34 get their feet on top of those.
1:32:36 Ideally get some into their hands as well.
1:32:37 Get some cool compresses and get them onto people's face.
1:32:41 You could, of course,
1:32:42 also put a cool compress on the back of the neck,
1:32:44 on the top of the head.
1:32:45 That would be an especially good idea
1:32:47 if someone were hyperthermic
1:32:48 because of the way that cooling of the brain occurs
1:32:51 under conditions of hyperthermia.
1:32:53 But the key point here is that
1:32:56 just putting cold compresses or cold materials
1:32:58 onto somebody's torso is not going to be as efficient
1:33:01 as cooling those glabrous skin surfaces,
1:33:02 the bottoms of the feet, the palms of the hands,
1:33:04 and the upper half of their face.
1:33:06 Similarly, or I suppose to be more accurate,
1:33:09 I should say, conversely,
1:33:10 there are times when it is desirable
1:33:13 to heat the core of the body.
1:33:15 And once again,
1:33:16 just simply throwing a hot towel over somebody
1:33:18 is not going to be the most efficient way.
1:33:21 If someone is hypothermic, they're too cold,
1:33:24 it is not a problem to cover them with a blanket.
1:33:27 But ideally what you do is you use some warm object
1:33:33 or warm fluid to warm the bottoms of their feet,
1:33:36 their hands, and the upper half of their face.
1:33:38 Of course not so warm that you burn those skin surfaces.
1:33:41 This has actually been examined in studies
1:33:43 from the Heller Lab.
1:33:44 Turns out that, for instance,
1:33:45 to get people out of anesthesia,
1:33:47 it is beneficial to warm their core body temperature.
1:33:51 And of course there is fever,
1:33:52 which you should know is an adaptive response.
1:33:55 While fever is uncomfortable,
1:33:57 and in fact often involves a mismatch
1:33:59 between our perception of our shell
1:34:01 and a perception of our core temperature.
1:34:03 In other words,
1:34:04 there are times when our body temperature is really high,
1:34:05 we have a fever, and yet we're shivering and we're cold.
1:34:08 And that's because under conditions of fever,
1:34:10 the immune system liberates certain molecules
1:34:13 that impact, and in some ways,
1:34:16 intentionally disrupt the preoptic area, the POA,
1:34:19 and the way it normally functions
1:34:21 so that it can override peripheral signals
1:34:24 and simply try and heat the body
1:34:25 and kill whatever pathogen has infected the body.
1:34:29 So for those of you that think about fever
1:34:32 as always a bad thing, it's not.
1:34:34 Now, of course we don't want our core body temperature
1:34:36 to go so high that tissues of the brain and body are damage.
1:34:39 This is one reason why, if a fever ever goes above 103,
1:34:43 you need to start getting a little bit worried, 104.
1:34:46 There are times when you need to call an ambulance
1:34:48 or go to a hospital,
1:34:49 you really need to employ cooling methods
1:34:52 of the sort that I talked about before
1:34:53 to prevent hyperthermia.
1:34:55 Of course, safe ranges for body temperature
1:34:57 vary between infants and adults.
1:34:59 So you can look those up online,
1:35:01 depending on the person's age, what is a safe range,
1:35:03 what is not.
1:35:04 But keep in mind that if you are taking compounds,
1:35:06 pills to reduce your fever,
1:35:08 you are actually short circuiting
1:35:10 the protective mechanism for burning up the pathogen.
1:35:13 And that's because most pathogens,
1:35:15 bacteria and virus, don't survive well at high temperatures.
1:35:18 In fact, in laboratories,
1:35:19 if we want to preserve a virus for use,
1:35:21 we put it into a freezer.
1:35:23 If we want to kill a virus, we heat inoculate it.
1:35:26 So in many ways, fever is your natural form
1:35:28 of heat inoculation designed to kill pathogens
1:35:31 of various kinds.
1:35:32 Now last, but certainly not least,
1:35:33 I want to refer to the study that I described
1:35:35 at the very beginning of this episode,
1:35:38 involving what's called local hyperthermia
1:35:41 in order to trigger a number of biological processes
1:35:44 in fat tissue in order to convert white fat to beige fat,
1:35:49 which is the metabolically active form of fat.
1:35:51 Many of you, or at least some of you,
1:35:53 should be familiar with the fact
1:35:55 that deliberate cold exposure
1:35:57 can increase brown fat stores,
1:35:59 these mitochondrial dense fat stores that can, in turn,
1:36:02 allow a person to feel more comfortable
1:36:05 in cold temperatures, water, or otherwise,
1:36:07 and increase core metabolism.
1:36:10 I talked about this in the episode on cold,
1:36:12 but very briefly, the general protocol, again,
1:36:14 is to get 11 minutes total per week of uncomfortable,
1:36:17 yet safe deliberate cold exposure,
1:36:19 either through ice bath, cold shower,
1:36:21 cold immersion up to the neck,
1:36:23 or some other form of cold exposure.
1:36:26 That triggers increases in brown fat.
1:36:29 That's been beautifully shown by Dr. Susanna Søberg.
1:36:32 And that increase in brown fat
1:36:34 in turn increases core metabolism
1:36:36 and one's ability to feel comfortable in cool temperatures.
1:36:40 This was a study done in humans,
1:36:42 and there's now ample evidence from animal models
1:36:44 to support that this is a general phenomenon
1:36:47 that I think most people could use and benefit from.
1:36:50 Local hyperthermia is a distinctly different phenomenon.
1:36:53 It involves heating a particular surface of the body
1:36:56 as a way to convert the white fat at that location
1:37:00 to beige fat, which in turn leads to more systemic increases
1:37:04 in thermogenesis and increases in metabolism,
1:37:07 and believe it or not, in fat loss.
1:37:09 Now, the study that I'm referring to
1:37:11 is a very recent study that was published,
1:37:12 again, in this terrific apex journal, Cell,
1:37:16 Cell Press Journal.
1:37:17 And again, one of the three top journals,
1:37:19 Nature, Science, and Cell are the three top journals.
1:37:21 Top because they're the most competitive,
1:37:23 but also generally, not always,
1:37:25 but generally the most stringent
1:37:27 in terms of the review process.
1:37:28 Papers that make it into these three journals
1:37:30 generally are of very, very high quality.
1:37:32 And certainly enough people see them that
1:37:34 if they're not of high quality,
1:37:35 they get shot down pretty quickly in a short amount of time.
1:37:37 Whereas papers in other journals
1:37:39 can sometimes last a long time
1:37:40 before they're ever replicated, et cetera.
1:37:43 The title of this paper
1:37:44 is "Local Hyperthermia Therapy Induces Browning of White Fat
1:37:48 "and Treats Obesity."
1:37:50 This was a study that was performed on mice and humans
1:37:54 in the same study.
1:37:55 What this study involved was heating
1:37:57 of a local patch of skin to 41 degrees Celsius,
1:38:00 which is a 105.8 degrees Fahrenheit,
1:38:04 but not damaging the skin.
1:38:06 So the methods of heating
1:38:08 did not involve placing something
1:38:10 on the skin that would damage it.
1:38:12 In fact, in the study on the mice,
1:38:13 they used this kind of clever molecular chicanery
1:38:17 in order to do it.
1:38:18 And in humans, they used a thermocouple
1:38:20 that would allow them to heat the skin up
1:38:22 just locally in particular locations on the body
1:38:25 that I'll talk about in a moment.
1:38:27 They refer to this process as LHT, or local heat therapy.
1:38:33 The reason they did this is worth considering.
1:38:36 It's long been known from clinical data.
1:38:40 And in fact, from a bit of research data
1:38:42 that people that experience burn on a small,
1:38:46 or unfortunately in some circumstances,
1:38:48 significant portion of their body
1:38:50 experience overall decreases in body fat
1:38:54 and increases in metabolism that can last many years,
1:38:58 Now, of course, is not reasonable nor would one
1:39:01 ever want to induce burn in order to induce fat loss.
1:39:05 But the observed increases in metabolism and fat loss
1:39:08 in response to skin surface burn
1:39:11 couldn't be explained by reductions in activity
1:39:14 related to the burn, for instance.
1:39:17 And in fact, there are molecular pathways
1:39:19 related to something called UCP1,
1:39:22 which is uncoupling protein one.
1:39:24 I talked about this also in the cold episode,
1:39:25 but don't worry if you didn't see that episode,
1:39:27 or if you choose not to.
1:39:28 UCP1 has the ability to increase mitochondrial function
1:39:34 in ways that increase core body temperature overall,
1:39:37 in particular, in beige and brown fat,
1:39:39 which are these fat cells that exist
1:39:42 generally along our spine, and in particular,
1:39:44 in the upper part of our back
1:39:46 and around our neck and clavicles.
1:39:48 And they're responsible for acting as this sort of a candle,
1:39:51 or I should say the fuel or the fat of a candle
1:39:55 that can be burned up to manufacture heat in the body.
1:40:00 So, if you normally think about fat
1:40:02 and you think about blubbery fat,
1:40:03 you're thinking about white fat,
1:40:05 which again is just a storage site.
1:40:06 Beige fat and brown fat exist at just a few locations,
1:40:09 mainly internally, around our spinal cord and our clavicles,
1:40:13 and those fat stores are responsible
1:40:15 for generating heat in our body.
1:40:16 So they're a very metabolically active form of fat.
1:40:20 Small children have a lot of brown fat and beige fat,
1:40:23 in particular because very young children can't shiver.
1:40:27 A number of you probably didn't know that,
1:40:28 but very young children can't shiver,
1:40:30 so they need some way to generate heat
1:40:31 in order to make sure that they stay alive
1:40:33 if they were ever to get cold.
1:40:35 This is also probably the reason why little kids
1:40:37 can run around on a cold day outside without their shirt on
1:40:39 and they don't even seem to notice,
1:40:40 whereas adults are freezing cold.
1:40:43 As we get older, the amount of beige and brown fat
1:40:45 tends to either reduce or shrink or disappear entirely.
1:40:51 It's still debated which happens.
1:40:53 But we know that white fat can be converted
1:40:55 to this more metabolically active form of beige fat
1:40:59 by deliberate cold exposure,
1:41:02 according to the protocol I talked about earlier,
1:41:04 and now it seems, based on this new study,
1:41:07 that local heating of skin tissue can also induce UCP1
1:41:12 and the effects of UCP1 on increasing mitochondria.
1:41:15 And in fact, that local hyperthermia, 41 degrees Celsius,
1:41:20 that is 105.8 degrees Fahrenheit,
1:41:23 can actually induce the conversion
1:41:25 of white fat to beige fat.
1:41:28 Now that's pretty interesting,
1:41:29 and I can already predict the way this is probably going to go
1:41:31 in the kind of wellness and biohacking
1:41:33 and longevity communities.
1:41:34 I'm sure that pretty soon there are going to be
1:41:36 people putting heating pads
1:41:37 on different fat pads of theirs on their body,
1:41:40 trying to reduce,
1:41:40 or at least convert the white fat into beige fat.
1:41:43 And who knows, maybe that'll work.
1:41:44 There have not been many controlled studies of this yet.
1:41:47 This is the first, at least to my knowledge,
1:41:49 of such studies looking at this in non-burn conditions.
1:41:53 Nonetheless, the data are mechanistically
1:41:56 even more interesting than this whole business
1:41:58 about UCP1, and here's why.
1:42:01 Local hyperthermia,
1:42:03 using the protocol that I described before,
1:42:06 resulted in the increase of a promoter,
1:42:09 which is essentially a mechanism
1:42:11 by which certain genes regulate their activity.
1:42:14 This is a DNA binding of something called HSF1.
1:42:18 We don't have to go too deep into the mechanism here
1:42:21 or the nomenclature,
1:42:21 but HSF stands for heat shock factor one.
1:42:25 And HSF1 binding to a particular location
1:42:30 in the genome allowed for a different molecule
1:42:35 with a very long name.
1:42:36 I'll just tell it to you for fun,
1:42:37 but you can just let the numbers and letters stream by.
1:42:40 It's not important.
1:42:41 HNRNPA2B1, shortened to A2B1,
1:42:45 which frankly is not that short to begin with, A2B1,
1:42:48 is still a name that should be meaningless
1:42:49 to most everybody, but here's what's really cool.
1:42:52 A2B1 is directly involved in glucose and lipid metabolism
1:42:57 and regulates the genes that control
1:42:59 glucose and lipid metabolism.
1:43:01 So here we have a situation where local heating of skin
1:43:04 converted a metabolically sluggish or inactive cell type,
1:43:08 the white fat cell, into the metabolically charging,
1:43:13 so to speak, beige fat cell, which in turn
1:43:16 led to systemic, meaning body-wide increases in metabolism,
1:43:20 through two mechanism.
1:43:21 One mechanism is this increase in UCP1,
1:43:24 which for those of you that want to know,
1:43:26 UCP1 causes shifts in the way
1:43:28 that potential energy is pushed from the protons
1:43:32 through the mitochondria,
1:43:33 basically more mitochondrial function,
1:43:34 which means more ATP,
1:43:36 which means cells are more active,
1:43:37 AKA, increased metabolism,
1:43:39 and increases in things like heat shock factor one and A2B1,
1:43:43 which are involved in lipid
1:43:44 and glucose metabolism and regulation.
1:43:46 So I want to be very clear,
1:43:48 this study does not say that spot reduction
1:43:51 is possible with local heating of tissue.
1:43:54 I just can see it now that once this paper
1:43:56 gets out into the press, people are going to say,
1:43:58 oh, heating up a certain patch of skin
1:44:00 is going to burn fat or convert fat
1:44:02 to some other cell type at that location.
1:44:04 Sorry, that's not the way it works.
1:44:07 They did observe increases in beige fat cells
1:44:11 at certain locations in the body.
1:44:13 But those increases in beige fat
1:44:15 occurred where beige fat cells always reside,
1:44:18 around the spine, the upper neck,
1:44:20 the clavicles, and so on.
1:44:22 This is exciting because it provides
1:44:24 yet another potential mechanism
1:44:26 in addition to deliberate cold exposure
1:44:28 to increase beige fat,
1:44:30 meaning the metabolically active form of fat cell.
1:44:34 It also nicely provides a mechanism,
1:44:36 or at least a potential mechanism,
1:44:38 for the observation that burn,
1:44:41 either small patch of skin being burned,
1:44:44 or again, sadly large patches of skin being burned,
1:44:47 leading to these very extreme and very long lasting
1:44:52 increases in body fat loss and metabolism.
1:44:56 What, if anything, should you do with this information?
1:44:58 Well, first of all, I want to very much caution people
1:45:02 about putting anything so hot that it can damage
1:45:05 the surface of your skin onto your skin.
1:45:08 That would be a terrible idea.
1:45:10 However, I do predict a time not too far from now
1:45:14 where people will start to explore the use
1:45:17 of local skin heating as a means
1:45:20 to increase the conversion of white to beige fat,
1:45:24 and in turn for beige fat stores
1:45:26 to increase metabolism overall,
1:45:28 and maybe even improve glucose metabolism and thermogenesis.
1:45:31 If you'd like more detail else about this study,
1:45:33 we will provide a link to it in the show notes caption.
1:45:36 I should mention that the study,
1:45:38 at least the portion of the study
1:45:39 that was focused on humans,
1:45:41 involved roughly equal numbers of males and females.
1:45:44 The subjects followed their normal daily schedule,
1:45:47 including time and composition of meals, they say,
1:45:49 rest and active hours, et cetera, et cetera.
1:45:52 The local hyperthermia therapy was done
1:45:54 in the following way.
1:45:55 Here I'm paraphrasing from their methods section.
1:45:58 Subjects were seated in an upright posture.
1:46:00 They were wearing a standard test robe
1:46:03 with the head and neck and shoulders unclothed
1:46:05 and one meter away from a thermal imaging camera,
1:46:08 which could basically measure the temperature
1:46:10 at their skin surface to make sure
1:46:11 that it remained constant across subjects and yet safe.
1:46:15 The supraclavicular fat deposits,
1:46:18 meaning the upper shoulders and upper back area,
1:46:21 were exposed to this thermal source,
1:46:22 again, 41 degrees for 20 minutes.
1:46:26 So it was 41 degrees for 20 minutes.
1:46:29 And their core temperatures and skin temperatures
1:46:31 were monitored before and after
1:46:34 this local hyperthermic therapy.
1:46:35 The subjects were exposed to this local hyperthermia therapy
1:46:39 three days per week, separated by day,
1:46:41 Monday, Wednesday, and Friday,
1:46:42 so they had weekends off, for five weeks total,
1:46:46 after which their data were collected.
1:46:48 And the study has a number
1:46:49 of other really interesting features
1:46:50 that are sure to lead to increased understanding
1:46:53 of both mechanism and new protocols,
1:46:55 such as analysis of the genes and proteins
1:46:57 that are activated downstream
1:46:59 of this local hyperthermia therapy.
1:47:01 I find these data incredibly interesting,
1:47:03 in part because of the ways
1:47:04 that local hyperthermia therapy
1:47:06 mimics deliberate cold exposure therapy.
1:47:09 Same downstream mechanisms, UCP1,
1:47:10 and some of the other pathways are involved,
1:47:13 and all of that points to a somewhat new,
1:47:15 but certainly an important concept.
1:47:18 Many of you have probably heard of hormesis,
1:47:19 which is the subjecting of one's self,
1:47:22 or others, I suppose,
1:47:23 to enough stress to induce an adaptation of some kind.
1:47:27 So hormesis is the reason why
1:47:29 if you get into cold water repeatedly,
1:47:32 at first, it's very painful psychologically,
1:47:34 and over time you get used to it.
1:47:36 You never get completely used to it,
1:47:37 but you get more used to it.
1:47:38 Hormesis is also used to describe the adaptation
1:47:42 to cardiovascular exercise or to the hard rep sets
1:47:46 of resistance training and the growth of muscles
1:47:48 or the strengthening of muscles
1:47:49 or the improvement in cardiovascular function
1:47:50 to endurance exercise and so forth.
1:47:52 Hormesis is a somewhat common term nowadays.
1:47:55 If you haven't heard it, now you've heard it.
1:47:58 In this paper they describe what is called mitohormesis,
1:48:01 which is, in essence,
1:48:02 the fact that any number of different stressful stimuli,
1:48:05 provided they activate UCP1
1:48:07 and some of these other pathways that I just described,
1:48:10 like HSF1, can induce changes in the mitochondria
1:48:13 that lead to increases in metabolism.
1:48:16 So it shouldn't surprise us that cold and heat
1:48:20 can both lead to increases in metabolism and conversion
1:48:23 of white fat to beige fat.
1:48:25 It shouldn't surprise us because both pathways are stress.
1:48:28 Local hyperthermia is stress.
1:48:30 Burn certainly is stress.
1:48:32 Sauna is a form of stress.
1:48:34 Deliberate cold exposure is a form of stress.
1:48:38 Exercise is a form of stress.
1:48:39 And the adaptation to those stressors is not infinite.
1:48:43 All of those protocols, any protocol for that matter,
1:48:46 is going to be effective
1:48:47 because it's going to converge
1:48:48 on an existing internal biological mechanism.
1:48:51 So there's no unique mechanism for each protocol.
1:48:55 Each protocol that I've talked about today,
1:48:57 whether or not it's five minutes or 20 minutes
1:48:58 or four times in a day
1:49:00 or three times per week or seven times per week
1:49:02 is tickling or pushing or stomping, if you will,
1:49:06 on a given pathway and really activating it
1:49:08 to a mild or to a severe degree.
1:49:10 What I've tried to do
1:49:11 is to illustrate the general mechanisms
1:49:14 by which heat in particular
1:49:16 can activate certain biological pathways
1:49:18 so that you can devise protocols
1:49:20 that are going to be optimal for you and your needs.
1:49:23 So just to briefly recap,
1:49:25 if you want to get the greatest growth hormone increases,
1:49:28 do sauna or other deliberate heat exposure fairly seldom,
1:49:33 probably no more than once per week, maybe even less,
1:49:36 and do it a lot that day.
1:49:37 Just make sure that you break it up into multiple sessions.
1:49:39 In the study I described earlier they did four sessions,
1:49:42 30 minutes each.
1:49:43 But that was just once a week.
1:49:46 If you're interested in the cardiovascular benefits
1:49:49 and the potential longevity benefits of sauna,
1:49:51 well then it's clear that doing it three to four,
1:49:53 maybe even seven times per week
1:49:55 is going to be more beneficial
1:49:56 than doing it just one or three times per week.
1:49:58 It stands to reason that for those of you interested
1:50:00 in the general health effects of sauna,
1:50:03 about an hour per week broken up into three sessions
1:50:06 makes the most sense based on my read of the data.
1:50:09 And again, that range of 80 to 100 degrees Celsius
1:50:12 is going to be your guide.
1:50:13 And in terms of the mental health benefits,
1:50:15 it seems that getting a little bit uncomfortable
1:50:18 in that heat environment, sauna or otherwise,
1:50:21 provided it's safe, is going to be the best way
1:50:23 to access those mental health effects
1:50:25 by way of increasing dynorphine, which, as you recall,
1:50:29 will then increase the ability of endorphin
1:50:32 to have its positive effects on mood
1:50:34 after you get out of the sauna
1:50:36 or other deliberate heat exposure.
1:50:37 And in terms of timing, after a workout of any kind,
1:50:41 morning or afternoon,
1:50:43 or if you're not doing it after a workout,
1:50:46 certainly in the later part of the day
1:50:47 is going to be most beneficial
1:50:48 as it relates to sleep.
1:50:50 But of course, there's a caveat there,
1:50:51 which I will mention again,
1:50:53 which is that for those of you
1:50:54 that have no trouble sleeping 'cause you're exhausted
1:50:56 or you're just one of these phenomenal sleepers,
1:50:58 well then do it any time of day or night.
1:51:00 But for most people doing it later in the day
1:51:02 is going to be more beneficial
1:51:04 because of the post sauna cooling effect
1:51:07 and the relationship between cooling by a degree or more
1:51:10 as a way to enter sleep.
1:51:12 Thank you for joining me today for my discussion
1:51:14 about the science of heat and heating for health.
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