Billy's Colloidal Silver + Starfire Gold duo — A sauna is a small room heated to a high temperature so that the body warms up, sweats and then cools off again. The traditional Finnish sauna heats the air to roughly 80 to 100 °C at head height with low humidity, while infrared cabins and steam rooms deliver heat in different ways. Most of the research behind talk of sauna benefits comes from long-running Finnish population studies, which found that frequent sauna use was statistically associated with lower rates of fatal cardiovascular events, without proving that the sauna itself was the cause.
It matters because sauna has moved from a Nordic custom to a staple of biohacking routines, and the claims around it now range well beyond what the data shows. The Finnish cohort is one of the larger observational datasets in the whole heat-and-cold debate, and short laboratory studies explain what heat does to the body during a session. Both have limits, and the safety record is clear on who should be careful.
Safety first. Drink water, cool down gradually and leave the sauna straight away if you feel dizzy, faint or unwell. Never combine sauna with alcohol. If you have heart disease (including unstable angina, a recent heart attack, severe aortic stenosis, uncontrolled high blood pressure or heart failure), get light-headed when you stand up, or are pregnant, consult a clinician before using a sauna. Children should always be supervised. Men trying to conceive may want to discuss regular sauna use with a clinician.
What is a sauna, and how do the types differ?
A sauna is a heated room used for short bathing sessions, and the three common types differ mainly in how they deliver heat and how humid the air is.
The traditional Finnish sauna uses a stove, electric or wood-fired, to heat the air to about 80 to 100 °C at head height. The air is dry, with relative humidity around 10 to 20 percent, raised briefly when water is thrown on the hot stones to make a burst of steam, known in Finnish as löyly. A typical stay lasts 5 to 20 minutes and is followed by cooling off in a shower, a swim or fresh air, often repeated two or three times.
An infrared sauna uses infrared emitters that warm the body more directly, so the surrounding air can be kept at a lower temperature, as the Mayo Clinic's overview of infrared saunas explains. That makes it a genuinely different exposure, and it has far less long-term research behind it. It is also not the same thing as a red-light panel: red light therapy, or photobiomodulation, uses low-power light at specific wavelengths and is designed not to heat tissue, while an infrared sauna works through heat.
Steam rooms and Turkish baths sit at the opposite end: high humidity, often near saturation, at lower air temperatures.
What happens in the body during a sauna session?
During a session, skin and core temperature rise, blood vessels near the skin widen, sweating increases and the heart beats faster, a pattern that resembles moderate exercise but without the working muscles.
Jari Laukkanen, Tanjaniina Laukkanen and Setor Kunutsor reviewed this response in their 2018 paper in Mayo Clinic Proceedings. As the skin heats, blood is redirected toward it to shed heat and the heart works harder; the same Finnish group reports that heart rate can climb to around 120 to 150 beats per minute, comparable to light to moderate physical activity.
The best-documented single session is a 2012 study by Iguchi and colleagues in the Journal of Athletic Training. Twenty-five young adults sat for 30 minutes in a heated room at 73 °C. Core temperature rose by about 0.8 °C, heart rate reached about 131 beats per minute and blood pressure fell. In the 13 participants who gave blood samples, plasma noradrenaline rose 58 percent, the hormone prolactin rose 285 percent and the heat shock protein HSP72 rose by about 49 percent. It is a useful snapshot of acute physiology in healthy young people, not evidence of any long-term effect.
What are heat shock proteins?
Heat shock proteins are a family of "chaperone" proteins that cells make in larger amounts under stress, including heat, and that help other proteins keep or regain their correct shape.
Proteins only work when they are folded properly, and heat makes them prone to unfolding and clumping. Heat shock proteins bind to these vulnerable proteins and help them fold correctly or be cleared away. HSP70, and the inducible form HSP72 measured in the Iguchi study, are among the best known.
That is why heat shock proteins come up so often in sauna discussions. The honest position is that much of the interest comes from cell and animal research, and human data are small and short-term. A rise in HSP72 in a blood sample after one session shows that the body registers heat as a stress and responds to it. It does not show what, if anything, repeated rises mean for health over years, and claims that sauna-induced heat shock proteins "repair" the body or slow ageing go well beyond the evidence.
What did the Finnish sauna studies find?
The best-known evidence comes from the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD) in eastern Finland, where frequent sauna use was associated with lower rates of fatal cardiovascular events and death from all causes.
The landmark paper is Tanjaniina Laukkanen, Hassan Khan, Francesco Zaccardi and Jari Laukkanen, "Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events," published online in JAMA Internal Medicine in February 2015 and in print that April. The team followed 2,315 men aged 42 to 60, recruited between 1984 and 1989, for a median of 20.7 years. At the start, 601 men used a sauna once a week, 1,513 two to three times a week and 201 four to seven times a week.
After adjusting for other known risk factors, the men who used the sauna more often had statistically lower rates of sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease and death from any cause during follow-up. Longer sessions were linked to lower rates of the three cardiac outcomes, but not of death from any cause.
A 2018 follow-up in BMC Medicine, led by Tanjaniina Laukkanen, widened the lens to women. It studied 1,688 men and women from the Kuopio area, 51.4 percent of them women, with a mean age of 63, examined between 1998 and 2001 and followed for a median of 15 years. It reported a similar association between more frequent sauna use and lower rates of fatal cardiovascular events.
What the Finnish studies do and do not show
The Finnish studies show an association between sauna habits and outcomes in one population; they do not show that sauna causes those outcomes.
They are observational: nobody was assigned a sauna schedule, and habits were self-reported at the start of the study. Healthier people may simply use saunas more, a problem known as reverse causation, since someone with poor heart health or low energy is less likely to take frequent hot baths. Wealthier or more active people may also have more access to a sauna and more time to use it, and no statistical adjustment can remove every such factor, which researchers call residual confounding.
The population is also specific. In Finland sauna is a near-universal custom, and the KIHD participants used traditional Finnish saunas. Those results cannot be transferred to infrared cabins, which deliver heat differently and lack comparable long-term data, or to steam rooms. The researchers themselves have said further studies are needed, and until randomised trials exist, none of this makes sauna a substitute for medical care or a recommended therapy for any condition.
Is sauna safe? Who should be careful
For most healthy adults, a sauna used sensibly is low-risk, but it places real demands on the heart and circulation, and a few groups need a clinician's advice first.
Three habits cover most of the risk. Drink water before and after, because a session draws a meaningful amount of fluid out through sweat. Cool down gradually rather than leaping from the heat to standing and walking, since blood pressure can drop when blood has pooled in the skin. And leave immediately if you feel dizzy, nauseous, faint or unwell.
Alcohol is the single biggest avoidable hazard. In a Finnish forensic study of deaths in saunas between 1990 and 2002, half of those who died were under the influence of alcohol, which worsens dehydration, lowers blood pressure further and blunts the judgement that tells someone to get out.
People with heart disease, including unstable angina, a recent heart attack, severe aortic stenosis, uncontrolled high blood pressure or heart failure, should consult a clinician before using a sauna. So should people who get light-headed when standing up and anyone who is pregnant. Children should always be supervised.
Sauna and male fertility
Heat also affects sperm production. In a 2013 study in Human Reproduction, Garolla and colleagues had 10 men use a Finnish sauna at 80 to 90 °C for two 15-minute sessions a week for three months. Their sperm count and motility dropped markedly, and both fully recovered six months after the sessions stopped. The effect was reversible, but men trying to conceive may want to discuss sauna use with a clinician.
Billy Carson's reading
There is no Billy Carson lecture devoted to sauna, and this article does not attribute any sauna claim to him. Heat has come up on his podcast as part of the wider biohacking conversation, but no documented Carson position on sauna was found, so the evidence above is left to speak for itself.
Where his work does set the frame is in the site's pillar on biohacking for beginners, which presents his approach as consciousness-first: sleep, movement, food timing, breath and practices like heat or cold are maintenance for the body, valued for the energy and clarity they free up for meditation and inner work rather than as metrics to chase. Read that way, a sauna session sits alongside the science of sleep and everyday self-care as a deliberate pause, not a fix-all, with the same evidence-first caution the pillar applies to everything else.
Watch, read and go deeper
The biohacking topic hub gathers every evidence-led guide on the subject in one place. Start with biohacking for beginners for how sauna compares with cold exposure, sleep, fasting and exercise, then read the companion guides on breathwork and the Wim Hof Method, which covers the cold side of the heat-and-cold debate, and grounding, or earthing. If you are weighing an infrared cabin against a light panel, the guide to red light therapy explains why the two work in completely different ways.
Frequently asked questions
What are the main sauna benefits supported by research?
The strongest data are observational. In the Finnish KIHD cohort, men who used a traditional sauna more often had statistically lower rates of fatal cardiovascular events and death from all causes over about 20 years. These are associations, not proof of cause and effect, and people commonly report relaxation as the most immediate effect.
How hot is a Finnish sauna, and how long should a session last?
A traditional Finnish sauna runs at about 80 to 100 °C at head height with low humidity of around 10 to 20 percent. Typical stays last 5 to 20 minutes, separated by cooling off in a shower, a swim or fresh air. Leaving early if you feel unwell matters more than hitting a set time.
Is an infrared sauna the same as a traditional sauna?
No. Infrared saunas warm the body more directly with infrared emitters at lower air temperatures, while Finnish saunas heat the air itself. The long-term Finnish findings came from traditional saunas and cannot be transferred to infrared cabins, which have far less research behind them.
What do heat shock proteins do?
Heat shock proteins are chaperone proteins that help other proteins hold their shape under stress such as heat. A 2012 study found HSP72 rose by about 49 percent after a 30-minute session at 73 °C. Most of the wider interest comes from cell and animal studies, and long-term human data are lacking.
Who should avoid the sauna or check with a clinician first?
People with heart disease, including unstable angina, a recent heart attack, severe aortic stenosis, uncontrolled high blood pressure or heart failure, should consult a clinician first, as should anyone who is pregnant or gets light-headed on standing. Never use a sauna after drinking alcohol, and always supervise children.
Sources and further reading
- Laukkanen T., Khan H., Zaccardi F. and Laukkanen J.A., "Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events," JAMA Internal Medicine, 2015.
- Laukkanen T. et al., "Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study," BMC Medicine, 2018.
- Laukkanen J.A., Laukkanen T. and Kunutsor S.K., "Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence," Mayo Clinic Proceedings, 2018.
- Iguchi M. et al., "Heat stress and cardiovascular, hormonal, and heat shock proteins in humans," Journal of Athletic Training, 2012.
- Garolla A. et al., "Seminal and molecular evidence that sauna exposure affects human spermatogenesis," Human Reproduction, 2013.
- Kenttämies A. and Karkola K., "Death in sauna," Journal of Forensic Sciences, 2008.
- Mayo Clinic, consumer health guidance on infrared saunas.
This article is for general information. Talk to a qualified clinician before starting regular sauna or heat therapy, especially if you have a heart condition, low blood pressure or are pregnant. These statements have not been evaluated by the Food and Drug Administration. This content is for information only and is not medical advice.
