Inside Your Cells
Heat Shock Proteins, Inflammation, and Immunity Benefits
When we discuss saunas, we often focus on how they relax us or support heart health. But there are even more interesting things occurring below the surface, at the cellular level. When we’re sitting in that intense, dry heat, we aren’t just feeling good, our body begins to change gears that influence our cells, proteins, immune function, and inflammation.
Much of what we know has been learned from traditional Finnish sauna studies, specifically studies focused on long-term sauna use. Let’s take a closer look at what regular sauna bathing could possibly impact on the cellular level.
Heat Shock Proteins
When our body heats up due to exercise or sauna bathing, we initiate a stress response in the body. Part of that stress response is to produce heat shock proteins (HSP), which function somewhat like quality control workers within our cells.
The first thing I want to mention is the usage and benefits of heat shock proteins (HSPs). These proteins help other proteins to fold correctly, repair damage to proteins, and maintain a functional state under stress. Even though that sounds small, it is important. Abnormal protein folding, particularly in the brain, is associated with some serious neurological diseases, including Alzheimer’s and Parkinson’s. HSPs play a role in maintaining a stable cellular environment, which scientists refer to as protein homeostasis.
Interestingly, one study found that repeated sauna use led to the expression of specific HSPs and heat shock factors (HSFs) in semen, indicating sauna-induced adaptations may have impacts beyond what we initially presumed.
Inflammation & Oxidative Stress
Chronic inflammation and oxidative stress are related with a long list of modern-day health-related issues (e.g. heart disease, cognition). Strikingly, sauna bathing seems to moderate both.
Regular Finnish Sauna bathing has been linked to a decreased number of inflammatory markers (C-reactive protein (CRP), fibrinogen and leukocytes). Additionally, some studies document reductions in certain reactive oxygen species and proinflammatory pathways. Also, sauna bathing may increase the body’s innate antioxidant defenses.
That said, the research isn’t 100% aligned. While there are many studies that show decreased oxidative stress, there are some studies that show an initial increased period of oxidative stress. Still, many scientists posit that the net overall effect is likely beneficial, especially in the long run, and relevant to brain health. Less inflammation in the brain may be part of the reason sauna bathers experience better cognition.
Immune Support: Why Sauna Bathers Tend to be Sick Less
There is an emerging body of research indicating that sauna bathing can act to support immune function, and not just because you feel yummy and toasty warm. In fact, one study found that people who bathed on a regular basis in a sauna, reduced their odds of catching the biomarkers of the common cold by half over a 3-month period.
Other longitudinal studies have linked frequent sauna bathing (2 – 7 times/week) with reduced risk of respiratory illnesses such as asthma, chronic obstructive pulmonary disease (COPD), and even pneumonia.
The theory is that consistent exposure to extreme heat conditions—while a sauna bath temperature can range from 80 – 100ºC—will condition the immune system the same way exercise does, and that exposure to heat acts as a mild stressor. Upon returning from the sauna, the body serves to adapt and build the ability to respond stronger when challenged.
Detoxification: A Frequently Misunderstood Subject
Let’s talk about detoxification. The idea of sauna therapy to “sweat your toxins out” is widely held, but also very controversial.
On one hand, research indicates that sweating can help eliminate small amounts of toxic substances, with heavy metals such as lead, mercury, and arsenic being among the small amounts one can sweat out. Some research even indicates that sweat can excrete synthetic chemicals, such as BPA, phthalates, flame retardants, and certain pesticide residues, at times with faster rates than one could urinate the chemicals out of their system.
That said, a systematic review published in 2019 confirmed that sweating, as a means of detoxification by sauna sweating alone, is not an evidence-based detoxification strategy. Most of the over-the-top claims of detoxification come from personal stories, rather than valid studies that are grounded in science. Simply stated, you may feel cleaner after sweating it out, but you cannot fully and completely detox your system by sweating it all out.
Important takeaway? The detoxification thing is still being explored. One thing is quite evident: there is value for a variety of sauna uses, some truly evidenced and some under review.
Final Thoughts
It may feel like you’re just sitting in the heat and relaxing, but sauna bathing initiates a long chain reaction of cellular processes that can support anything from protein permeability to immune resilience. While many of these effects, such as detoxification, are still being investigated, several others, like reduced inflammation and enhanced immune defense, are increasingly backed by research.
That’s just one dimension of sauna use and how it influences the body. If you’re interested in what other functions are happening behind the scenes, continue reading this Health Benefits of Sauna series; we have only begun.
Sauna Health Benefits Research Resources
We asked, what research is actually out there? How do we know what is sales words, and what is grounded research. Through that, we decided to compile a library of all the literature on the health benefits of sauna.
Sauna & Heart Health
Sauna benefits to vascular endothelial cardiac function
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Vascular endothelial function improved: Sauna therapy significantly increased flow-mediated dilation (%FMD), showing better blood vessel function.
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Cardiac stress decreased: Levels of BNP (a marker of heart failure severity) dropped after two weeks of sauna treatment.
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Clinical symptoms improved: 17 out of 20 patients reported better symptoms and overall cardiac function after repeated sauna sessions.
Sauna & Heart Health
Sauna effect on heart rate variability
Significant plasma volume increase: Post-exercise sauna use expanded plasma volume by about 18% after just four sessions.
Heart rate and HRV changes were small or unclear: Only minor reductions in resting heart rate and small shifts in HRV markers were observed, with unclear correlations to plasma volume.
Sauna enhanced training adaptation: Adding sauna to normal training improved physiological capacity in trained cyclists beyond training alone.
Sauna & Arthritis
Infrared Sauna in Arthritis and Spondylitis
Pain and stiffness significantly reduced: During IR sauna sessions, both RA and AS patients showed marked decreases in pain and stiffness (p < 0.05 and p < 0.001, respectively).
No adverse effects or disease flare-ups: Treatments were well tolerated, with no signs of increased disease activity or other side effects.
Short-term comfort, modest long-term benefit: Patients reported feeling comfortable and relaxed during and after sessions. Clinical improvements persisted during treatment but faded post-therapy.
Sauna & Heart Health
Advertising in Saunas and Positioning
Digital promotion gained momentum: Social media emerged as a powerful channel for business growth, offering wide reach and precise audience targeting for tailored advertising.
Marketing strategies adapted post-crisis: The health crisis reshaped the economy and reduced ad spending, pushing companies—including sauna brands—to prioritize customer acquisition through focused advertising efforts.
Medicinal benefits reinforced: Positioning centered on health advantages, with studies showing that 2–3 or ≥4 weekly sauna sessions significantly reduced the risk of respiratory diseases compared to ≤1 session per week.
Sauna & Exercise Recovery
Effects of Thermal Modalities on Exercise Recovery
- Effectiveness depends on participant type: Warm Water Immersion (WWI) was found to be more effective for athletes in increasing recovery and preventing muscle cell damage. Conversely, Infrared Sauna (IRS) and Traditional Sauna (TRS) were more effective for recovery in nonathletes.
- Significant reduction in fatigue markers: All recovery modalities played a role in reducing the blood lactate level (BLL) after physical activity, and all modalities were effective in significantly reducing heart rate (HR) in both groups after exercise.
- WWI minimized perceived pain: The WWI modality resulted in the least amount of pain in both athletes and nonathletes. Passive recovery (PAS), in contrast, tended to cause severe pain.
Sauna & Mortality
Sauna Use and Mortality Reduction
- High frequency reduces overall and cardiovascular death: Increased frequency of sauna bathing is associated with a reduced risk of sudden cardiac death (SCD), fatal coronary heart disease (CHD), fatal cardiovascular disease (CVD), and all-cause mortality.
- Maximum protective effect seen in frequent users: Compared with men bathing once per week, those reporting 4 to 7 sauna sessions per week had a significantly lower adjusted hazard ratio for SCD (0.37) and experienced a 40% reduction in all-cause mortality.
- Longer duration also lowers SCD risk: Longer sauna sessions were inversely associated with fatal cardiac events; sessions lasting more than 19 minutes were linked to a 52% lower risk of SCD compared to sessions lasting less than 11 minutes.
Sauna & Therapies
Benefits and Scope of Passive Heat Therapies
- Finnish Sauna is the most studied modality: Finnish saunas are the most widely studied passive heat therapy, characterized by high temperatures (80–100°C) and dry air (10–20% relative humidity).
- Demonstrated health benefits and disease prevention: Finnish saunas have robust evidence showing they decrease the risk of hypertension, cardiovascular disease (CVD), dementia, and respiratory conditions. They may also improve sleep, mental well-being, and longevity.
- Potential for synergistic effects and mechanism: Passive heat therapies may augment the beneficial effects of physical activity and their positive effects are linked to anti-inflammatory, cytoprotective, and anti-oxidant properties.
Sauna & Respiratory Diseases
Sauna Reduces Respiratory Diseases
- Lower respiratory disease risk: Men taking 2–3 sauna sessions per week showed a 27% reduction in respiratory disease incidence compared to ≤1 session.
- Stronger benefits with higher frequency: Those bathing ≥4 times weekly had up to a 41% lower risk, indicating a dose-response relationship.
- Pneumonia risk reduced: Frequent sauna users experienced 28–37% lower pneumonia incidence after long-term follow-up and risk adjustment.
Sauna & Health Benefits
Finnish Sauna Health Benefits
- Offers vascular and nonvascular benefits: Traditional Finnish sauna bathing, characterized by high temperatures (80°C–100°C) for brief periods, is linked to reduced risk of vascular diseases like high blood pressure and cardiovascular disease (CVD), as well as nonvascular conditions such as pulmonary diseases.
- Physiological effects mimic moderate physical activity: The physiological responses during an ordinary sauna bath correspond to those produced by moderate- or high-intensity physical activity, such as walking. This is linked to mechanisms like reduction in systemic blood pressure, improvement in endothelial function, and beneficial modulation of the autonomic nervous system.
- Sauna is generally safe, even for stable CVD patients: Sauna bathing is a safe activity and can be used in patients with stable CVD, provided it is used sensibly, though patients with unstable disease conditions like recent myocardial infarction or uncontrolled hypertension should exercise caution.
Sauna & Dementia Risk
Sauna Bathing Frequency and Dementia Risk
- Frequent use suggests reduced dementia risk: A long-term prospective cohort study suggests that frequent sauna bathing may be associated with a reduced subsequent risk of dementia in both men and women.
- Highest protection seen in moderate users: Individuals reporting 9–12 sauna sessions per month (approximately three times per week) had a significantly lower adjusted hazard ratio for dementia (HR=0.47) during the first 20 years of follow-up, compared to those bathing 0–4 times per month.
- Temperature influences protective effects: The most favorable sauna temperature range for dementia protection was 80–99 ◦C. Bathing at temperatures higher than 100 ◦C, however, was associated with an elevated risk during the initial 20 years of follow-up.
Dry Sauna & Clinical Effects
Clinical Effects of Regular Dry Sauna
- Review found benefits across multiple conditions, but studies were heterogeneous: The systematic review included 40 clinical studies involving regular dry sauna bathing (Finnish-style and infrared) and concluded there is potential evidence of health benefits across cardiovascular disease (CVD), rheumatological, pain, and respiratory conditions.
- Frequent sauna use linked to lower CVD and mortality risks: Frequent Finnish sauna use (4–7 sessions per week) was strongly associated with a reduced risk of sudden cardiac death (63% reduction), dementia (66% reduction), and a 40% reduction in all-cause mortality over a 20-year period in middle-aged men.
- Generally safe, though reversible spermatogenesis impairment noted: Regular dry sauna bathing appears to be safe and generally well-tolerated in clinical settings, but one study showed reversible reduction in sperm count and motility in healthy men after repeated sessions, with all effects reverting to normal six months after cessation.
Sauna & Health Benefits
Cardiovascular and Other Health Benefits of Sauna
- Focus on Traditional Finnish Sauna: This passive heat therapy is characterized by exposure to high environmental temperatures (80°C–100°C) and dry air (10%–20% relative humidity), traditionally used for pleasure and relaxation.
- Linked to Reduced Risk of Vascular Disease and Mortality: Emerging evidence suggests sauna bathing reduces the risk of vascular diseases such as high blood pressure and cardiovascular disease (CVD). Frequent use (4–7 sessions/wk) was associated with a reduced risk of sudden cardiac death and all-cause mortality.
- Physiological Effects and Safety Profile: The physiological responses produced during a sauna bath correspond to those of moderate- or high-intensity physical activity (like walking). Sauna bathing is generally safe for patients with stable CVD, but those with unstable conditions (e.g., uncontrolled hypertension) or those combining it with alcohol should exercise caution.
