If there's one scientist whose work I recommend everyone in the contrast therapy space should know, it's Dr. Susanna Søberg. Her research on cold water immersion and brown adipose tissue is the scientific backbone behind much of what we do at Contrast Collective. And this Huberman Lab episode is the single best distillation of her findings for a general audience.
What strikes me most about Søberg's framework is how she connects temperature exposure to something most people never think about: the activation threshold. Not everyone responds to cold the same way, and the research now suggests this isn't just about pain tolerance — it's about the baseline state of your autonomic nervous system. People who are already in a chronic state of low-level stress or sympathetic arousal tend to perceive cold as a greater threat. This means that for stressed, anxious individuals, the protocol matters even more — you need a gentler on-ramp, not a more aggressive one.
Here's what our knowledge base consistently shows across multiple sources, from Rhonda Patrick to Peter Attia to Søberg herself: the minimum effective dose for metabolic benefits from cold exposure is approximately 11 minutes per week, spread across at least two sessions. That's it. You don't need to be Wim Hof sitting in ice for hours. Eleven minutes, split thoughtfully through the week, activates brown fat, elevates noradrenaline, and begins retraining your thermoregulatory system. The diminishing returns curve kicks in surprisingly early.
The heat side of this equation is equally important, and here Søberg's protocol aligns beautifully with the Finnish research from Dr. Jari Laukkanen that we've indexed in our database. Laukkanen's long-term studies (tracking thousands of Finnish men over decades) show that sauna use 4–7 times per week at high temperatures correlates with dramatically reduced all-cause mortality, cardiovascular disease risk, and even dementia. The mechanism appears similar to what Søberg describes: heat stress proteins (HSP70, HSP90) are upregulated, cardiovascular demand mimics moderate aerobic exercise, and there's a powerful anti-inflammatory cascade.
What this episode adds that's often overlooked in the "should I do cold or heat" debate: they are synergistic, not competitive. Cold exposure activates the sympathetic nervous system and drives catecholamine release. Heat exposure does the same through a different pathway, while additionally triggering growth hormone and activating HSPs. When you alternate between them — contrast therapy — you get both sets of adaptations without having to choose. The "pump" effect from vasodilation and vasoconstriction cycling also improves vascular function over time in ways that neither heat nor cold alone produces as efficiently.
One nuance I want to highlight: the temperature of the cold matters more than the duration, up to a point. Water that feels "cold" but is actually 18–20°C will produce some response but activates brown fat far less than water at 10–12°C. Søberg's threshold for meaningful brown fat activation appears to be around 14°C or below. If your "cold plunge" isn't actually cold enough, you may be doing a lot of psychological work for less physiological payoff.
My recommendation: Use Søberg's minimum effective dose as your baseline — 11 minutes of cold per week (not per session), split across sessions, in water colder than 15°C. Pair it with at least 57 minutes of sauna per week. End your contrast sessions on cold when your goal is metabolic. End on heat when recovery is the priority. Track how you feel across two weeks, then adjust. Temperature is your training tool — learn to use it precisely.