The claim
“Sauna switches on heat shock proteins that slow aging.”
Stretched. In one sauna study, blood levels of heat shock protein 72 rose 48.7% on average after 30 minutes at 73°C. A review of 51 controlled heating studies found no change overall, and the idea that these proteins slow aging comes from animal research.
Updated Sep 24, 2026 · 2 studies reviewed
The claim pulls a real finding well past what the study showed.
People say it in places like these
Huberman Lab website
Heat shock proteins climb after 30 minutes at 73°C and help keep proteins from clumping as they do in Alzheimer's.
See an example ↗Rhonda Patrick's FoundMyFitness
Thirty minutes at 73°C raised heat shock proteins by 49%, and they stay high for 48 hours.
See an example ↗Peter Attia's blog
He ties heat shock proteins to a rare case of resilience against dementia and calls the chain speculative.
See an example ↗
The research found this
One sauna study supplies the numbers. At the University of Iowa, 25 young adults sat in random order for 30 minutes in a sauna-style chamber at 73°C on one day and at 26.1°C on another.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗ In the 13 who gave blood, the form of heat shock protein 72 that circulates outside cells rose 48.7% on average after the heat. The variation between people (±53.9%) was larger than the average rise.
Hot-water studies point in different directions. In people with type 2 diabetes who sat in 40°C water for an hour before a glucose test, blood heat shock protein 70 (HSP70) reached 402 pg/mL, against 203 pg/mL without heat.Source 2 · Crossover trialTiming of acute passive heating on glucose tolerance and blood pressure in people with type 2 diabetes: a randomized, balanced crossover, control trialJames TJ, Corbett J, Cummings M, et al.. Journal of Applied Physiology, 2021.Read the paper ↗PubMed ↗ An hour of hot water that held core temperature at 38.5°C or more changed neither blood nor cell levels in a second group with diabetes.Source 3 · Crossover trialAcute effect of passive heat exposure on markers of cardiometabolic function in adults with type 2 diabetes mellitusBehzadi P, Ravanelli N, Gravel H, et al.. Journal of Applied Physiology, 2022.Read the paper ↗PubMed ↗ Overweight men who spent an hour in 39°C water showed no change in the protein inside their immune cells, and after two weeks of sessions their blood level had fallen 17%.Source 4 · Crossover trialAcute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adultsHoekstra SP, Bishop NC, Faulkner SH, et al.. Journal of Applied Physiology, 2018.Read the paper ↗PubMed ↗
A 2025 meta-analysis pooled 51 controlled studies of heating without exercise and found heat shock proteins unchanged after one session or many.Source 5 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗ Heat aimed straight at a muscle does raise them in that muscle. In one study, two hours a day of deep heat from a shortwave diathermy device raised muscle HSP70 by 45% after six days.Source 6 · Clinical trialRepeated exposure to heat stress induces mitochondrial adaptation in human skeletal muscleHafen PS, Preece CN, Sorensen JR, et al.. Journal of Applied Physiology, 2018.Read the paper ↗PubMed ↗ Another found a 25% rise during 10 days of immobilization.Source 7 · Clinical trialDaily heat treatment maintains mitochondrial function and attenuates atrophy in human skeletal muscle subjected to immobilizationHafen PS, Abbott K, Bowden J, et al.. Journal of Applied Physiology, 2019.Read the paper ↗PubMed ↗
Heat also switches on the genes behind these proteins. In a depression trial, blood drawn 30 minutes after a session of medical whole-body heating showed more activity in several heat shock protein gene families than blood drawn after a sham.Source 8 · Clinical trialWhole-blood transcriptomic response to whole-body hyperthermia in participants with major depressive disorderAkonom TN, Allen MA, Begay TK, et al.. Brain, Behavior, & Immunity - Health, 2026.Read the paper ↗PubMed ↗
The dial reads 74°H for four reasons
How the reading adds up
20 + 20 + 22 + 12 = 74°H
EvidenceWhat kind of human evidence exists?
20/25Studies in people measured the proteins in blood and muscle, and none of them measured aging.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗Source 5 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗ For the aging part, the claim borrows from animal research.
ConsistencyHave other studies found the same thing?
20/25The one sauna study found a rise, and hot-water studies split. Pooled across 51 controlled studies, heat shock proteins didn't change after one heating session or many.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗Source 2 · Crossover trialTiming of acute passive heating on glucose tolerance and blood pressure in people with type 2 diabetes: a randomized, balanced crossover, control trialJames TJ, Corbett J, Cummings M, et al.. Journal of Applied Physiology, 2021.Read the paper ↗PubMed ↗Source 3 · Crossover trialAcute effect of passive heat exposure on markers of cardiometabolic function in adults with type 2 diabetes mellitusBehzadi P, Ravanelli N, Gravel H, et al.. Journal of Applied Physiology, 2022.Read the paper ↗PubMed ↗Source 5 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
MagnitudeDoes the claim match the size of the effect?
22/25The average rise of 48.7% came with a spread of ±53.9% between people.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗ Nobody has measured the slower aging that the claim promises.
DoseDoes the studied dose match how people use it?
12/25The sauna study held young adults at 73°C for 30 unbroken minutes.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗ That's longer than the 5 to 20 minutes a Finnish review gives for a typical round.Source 9 · ReviewCardiovascular and Other Health Benefits of Sauna Bathing: A Review of the EvidenceLaukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018.Read the paper ↗PubMed ↗
The claim drifts from the data here
The claim treats heat shock proteins as something every session switches on. Across 51 controlled studies they didn't budge, and in the one sauna study the person-to-person spread was bigger than the average rise.Source 5 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗
In the sauna study, 30 unbroken minutes at 73°C took rectal temperature to 38.5°C. A normal 10-minute round adds about 0.4°C to core temperature.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗Source 10 · Clinical trialTemperature and humidity independently influence thermoregulatory responses during Finnish sauna bathingLaatikainen-Raussi I, Mikkola T, Ihalainen JK, et al.. Temperature, 2026.Read the paper ↗PubMed ↗
Sauna studies in people stop at a blood test, and the promise of slower aging comes from animal work.
Put it to use
Treat heat shock proteins as an open question. If you want a sauna for your health, the evidence runs deeper for blood pressure than for anything measured inside cells.
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People also ask
How long do you need to sit in a sauna to raise heat shock proteins?
The one sauna study with published numbers used 30 unbroken minutes at 73°C. Blood heat shock protein 72 rose 48.7% on average, and the results varied widely from person to person.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗ A study that ran a series of ten saunas also measured HSP70, and its abstract doesn't report the values.Source 11 · Clinical trialThe effects of a single and a series of Finnish sauna sessions on the immune response and HSP-70 levels in trained and untrained menPilch W, Szarek M, Olga CL, et al.. International Journal of Hyperthermia, 2023.Read the paper ↗PubMed ↗
Do heat shock proteins slow aging?
That idea comes from animal research. Human studies haven't tied heat shock proteins raised by a sauna to slower aging, and a review of 51 controlled heating studies found the proteins unchanged overall.Source 5 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
Check these claims next
95°H
Hot air
“Sauna activates the FOXO3 longevity gene.”
We found no study that measured FOXO3 in people after a sauna or any other heat treatment. The claim ties that untested gene effect to a longevity link from one long-running Finnish study of men.
60°H
Stretched
“A sauna session raises your growth hormone 16-fold.”
The 16-fold rise came from ten men doing two hour-long saunas a day for a week, and it faded after the third day. One ordinary session gives a small, brief bump in younger men and none in older men.
36°H
Likely
“Regular sauna use helps you live longer.”
One long-running Finnish study ties frequent sauna use to fewer deaths. The 2015 paper put the most frequent bathers' risk of death 40% lower, and later papers with longer follow-up and broader groups put it about 14% lower. The link didn't show up in the fitter half of the men or in the women the study added later.
We cited these sources
- 01Iguchi M, Littmann AE, Chang SH, Wester LA, Knipper JS, Shields RK. Heat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in Humans. Journal of Athletic Training. 2012;47(2):184-190. doi:10.4085/1062-6050-47.2.184 PMID 22488284
- 02James TJ, Corbett J, Cummings M, Allard S, Young JS, Towse J, et al.. Timing of acute passive heating on glucose tolerance and blood pressure in people with type 2 diabetes: a randomized, balanced crossover, control trial. Journal of Applied Physiology. 2021;130(4):1093-1105. doi:10.1152/japplphysiol.00747.2020 PMID 33411640
- 03Behzadi P, Ravanelli N, Gravel H, Barry H, Debray A, Chaseling GK, et al.. Acute effect of passive heat exposure on markers of cardiometabolic function in adults with type 2 diabetes mellitus. Journal of Applied Physiology. 2022;132(5):1154-1166. doi:10.1152/japplphysiol.00800.2021 PMID 35323077
- 04Hoekstra SP, Bishop NC, Faulkner SH, Bailey SJ, Leicht CA. Acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults. Journal of Applied Physiology. 2018;125(6):2008-2018. doi:10.1152/japplphysiol.00407.2018 PMID 30335579
- 05Price BS, Lucas SJE, Akerman AP, Gilworth RE, Lucas RAI. Heat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysis. Experimental Physiology. 2025:EP092404. doi:10.1113/EP092404 PMID 41166412
- 06Hafen PS, Preece CN, Sorensen JR, Hancock CR, Hyldahl RD. Repeated exposure to heat stress induces mitochondrial adaptation in human skeletal muscle. Journal of Applied Physiology. 2018;125(5):1447-1455. doi:10.1152/japplphysiol.00383.2018 PMID 30024339
- 07Hafen PS, Abbott K, Bowden J, Lopiano R, Hancock CR, Hyldahl RD. Daily heat treatment maintains mitochondrial function and attenuates atrophy in human skeletal muscle subjected to immobilization. Journal of Applied Physiology. 2019;127(1):47-57. doi:10.1152/japplphysiol.01098.2018 PMID 31046520
- 08Akonom TN, Allen MA, Begay TK, Mason AE, Cole SP, Raison CL, et al.. Whole-blood transcriptomic response to whole-body hyperthermia in participants with major depressive disorder. Brain, Behavior, & Immunity - Health. 2026;54:101225. doi:10.1016/j.bbih.2026.101225 PMID 42004495
- 09Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence. Mayo Clinic Proceedings. 2018;93(8):1111-1121. doi:10.1016/j.mayocp.2018.04.008 PMID 30077204
- 10Laatikainen-Raussi I, Mikkola T, Ihalainen JK, Ahokas E. Temperature and humidity independently influence thermoregulatory responses during Finnish sauna bathing. Temperature. 2026;13(3):289-299. doi:10.1080/23328940.2026.2698162 PMID 42694940
- 11Pilch W, Szarek M, Olga CL, Anna P, Żychowska M, Ewa SK, et al.. The effects of a single and a series of Finnish sauna sessions on the immune response and HSP-70 levels in trained and untrained men. International Journal of Hyperthermia. 2023;40(1):2179672. doi:10.1080/02656736.2023.2179672 PMID 36813265