Dr. Bo Beard makes a simple but important point: this isn't a competition. Sauna versus hot tub is the wrong frame. The right frame is: what does your body need today, and which thermal tool delivers it?
That reframing matters. Most people approach heat therapy as either/or — they pick one and stick with it. But sauna and hot tub work through meaningfully different mechanisms, and understanding the difference lets you be intentional rather than habitual.
The cardiovascular and longevity data behind sauna is some of the most compelling in the thermal therapy space. Rhonda Patrick's work synthesizing the Finnish cohort studies — nearly 1,700 participants tracked over years — shows a 50% reduction in cardiovascular mortality for those using sauna four to seven times per week. The Alzheimer's numbers are equally striking: 66% lower risk compared to once-weekly users. These aren't marginal effects.
The mechanism Bo Beard highlights — heat shock proteins — is exactly why. When your core temperature rises significantly, misfolded proteins in your cells get either repaired or cleared out. You're doing cellular housekeeping. And the higher the ambient temperature, the more your core temperature rises, and the stronger that signal becomes. A traditional Finnish sauna at 220 degrees Fahrenheit achieves something physiologically that a 104-degree hot tub simply cannot replicate at equivalent exposure times.
Hot tubs have their own distinct advantage, though: hydrostatic pressure. The water pushes against your tissues from all sides, improving venous return and supporting lymphatic circulation. If you've been on your feet all day, or you've just finished a hard training session, that mechanical pressure does work that dry heat alone doesn't.
There's broad agreement on the fundamentals: heat increases heart rate, promotes vasodilation, puts the nervous system into parasympathetic mode, and supports recovery. Both modalities share that common ground. Where the literature diverges is in the intensity of the adaptive response. Heat shock protein induction, growth hormone release, the cardiovascular training effect — all of these are dose-dependent. Higher temperatures, held for appropriate durations, drive stronger adaptations. The hot tub is gentler. That's not a weakness; it's a different application.
Here's what I find underappreciated in Dr. Beard's transcript: the evening hot tub as a sleep protocol. Your core body temperature needs to drop to fall asleep deeply. If you spike it a couple of hours before bed — in a hot tub, sauna, or even a hot bath — your body's natural cooling response amplifies. You fall asleep faster, sleep deeper. This is the same mechanism Huberman has discussed extensively, and it's one of the most accessible sleep interventions available. No supplements. No blue-light blockers. Just heat, followed by time.
If you have access to both: use sauna for your cardiovascular and longevity protocol — three to four times per week, 15 to 20 minutes, high temperature. Use the hot tub for evening recovery and sleep priming — 104 to 105 degrees, 10 to 15 minutes, two hours before bed. If you only have one, you still have a tool. If you have neither, Bo Beard is right: exercise, fasting, and smart heat exposure from a shower will get you much of the way there.
The principle underneath all of this is the same one running through every thermal modality: controlled stress, followed by adequate recovery, produces adaptation. The sophistication isn't in picking the right machine. It's in understanding what your body needs, and matching the tool to the moment.