This article offers an in-depth exploration of sauna health benefits.
Historically, people in cold climates used saunas during winter to heat their bodies and induce relaxation.
Many believe that saunas offer an alternative therapy for promoting health and that sauna-induced sweating detoxifies the system (read: sauna and excretion of heavy metals).
We shall examine the research studies that appear to support claims about the health benefits of saunas, steam baths, and hot tubs.
Sauna benefits: The science-based evidence
A sauna is a heated room where people experience heat-induced sweating (perspiration) while relaxing.
Saunas temperatures generally range from 45°C to 100°C (113°F to 212 °F), depending on the type.
Traditional Finnish saunas are dry saunas heated to 150-195°F (65.6-90.56°C) at a relative humidity of 10-20%. Turkish-style saunas are wet saunas heated to 110-120°F (43-49°C) at higher humidities close to or equal to 100%.
Infrared saunas use infrared rays for heating the body at 120-140°F (49-60°C).
Here are some health benefits of sauna (passive heating) use based on evidence from research studies:
1. Sauna effect is similar to moderate-intensity exercise
But the researchers warned against people interpreting the study to mean they can take sauna as a substitute for aerobic exercise.
They concluded that saunas offer health benefits when combined with regular exercise.
Studies also suggested that sauna, steam baths, and hot baths have similar cardiovascular health benefits.
The cardiovascular health benefits are due to the ability of heat therapy to increase core temperature. It also increases metabolic and heart rate and improves blood flow.
2. Sauna reduces risk of cardiovascular disease-related death
Studies suggest that frequent sauna use significantly decreased cardiovascular disease-related mortality.
Laukkanen and associates (2015) investigated the relationship between the frequency and duration of passive heating and the risk of heart disease-related death.
The study looked at mortalities due to sudden cardiac death (SCD), fatal coronary heart disease (CHD), fatal cardiovascular disease (CVD), and all-cause mortality.
The participants included 2315 middle-aged (aged 42-60 years) Finnish men.
The authors concluded that increased sauna bathing frequency was associated with decreased risk of SCD, CHD, CVD, and all-cause mortality.
They reported that subjects who engaged in multiple sauna sessions a week (4-7 sessions) halved their risk of dying from cardiovascular disease (CVD) compared with those who had only one session a week.
3. Reduces cardiovascular risk in overweight women with PCOS
Ely and colleagues (2019) reported that passive heating offered multiple cardiovascular health benefits in sedentary and obese women.
According to the researchers, heat therapy (“repeated passive heat exposure”) reduced cardiovascular disease risk in obese women with polycystic ovary syndrome (PCOS).
The health benefits of sauna include:
- Reduced cardiovascular disease risk
- Improved blood pressure and arterial health
- Improved fasting blood glucose
- Reduced total cholesterol levels
- Alleviating inflammation
The authors reported that passive heating may help delay or prevent the onset of cardiovascular diseases. They proposed that more widespread use of saunas may reduce the healthcare burden associated with the high incidence of cardiovascular diseases.
The study involved obese women (BMI 41.3 ± 4.7 kg/m2) with PCOS who underwent 30 one-hour heat therapy sessions during 8-10 weeks.
Heat therapy reduced sympathetic activity and significantly improved the subjects’ cardiovascular risk profiles.
4. Sauna and congestive heart failure treatment
Tei and Tanaka (1996) found that passive heating may play a role in congestive heart failure treatment. The authors reported that heat therapy multiple times a week enhanced cardiac function in patients with chronic heart failure.
Miyamoto and associates (2005) investigated the safety and efficacy of repeated sauna bathing (60°C) in patients with chronic systolic congestive heart failure (CHF).
The study included 15 patients who underwent sauna bathing daily for 4 weeks. The authors reported improvement in the condition of 13 of the 15 hospitalized patients after 4 weeks.
The patients with improved health recorded lower systolic blood pressures without a heart rate increase. Echocardiography showed an improvement in left ventricular function, exercise tolerance, and respiratory function.
The researchers concluded that passive heating was safe for patients with CHF and that it improved disease symptoms.
They suggested that sauna bathing may offer effective adjunctive therapy in chronic systolic CHF.
5. Relieves symptoms of coronary heart disease (CHD)
Sauna bathing may reduce the risk of coronary heart disease (CHD) (also known as ischemic heart disease).
Coronary heart disease (CHD) refers to heart problems caused by narrowing or plaque buildup in the walls of the arteries (coronary arteries) that supply the heart muscles.
[Note: Waon therapy is a Japanese term for sauna therapy.]
The authors conducted a study to determine whether sauna (waon) therapy improved blood supply to heart muscles (myocardial perfusion) in patients with ischemia due to chronic total occlusion (CTO) of coronary arteries.
The study involved 24 patients with ischemic heart disease associated with CTO. The patients were divided into two groups. The first group (n=16) received daily waon (sauna) treatment for three weeks (60 °C far infrared-ray sauna bath for 15 min). The control group did not receive any passive heating.
Based on test results from myocardial scintigraphy tests to measure the severity of ischemia, the researchers reported that the waon therapy improved CTO-related myocardial ischemia.
They also reported an improvement in vascular endothelial function.
[Note: Endothelium is the thin membrane that lines the inside of blood vessels and the heart.]
The researchers concluded that waon therapy could play a complementary role in the treatment of patients with severe coronary heart disease lesions.
6. Sauna may improve arterial blood flow
Laukkanen and associates (2015) reported that frequent sauna reduced the risk of coronary heart disease (CHD) and other cardiovascular diseases.
The authors also reported that passive heating improved hemodynamic function (blood flow).
According to Brunt and colleagues (2016), sauna therapy improved endothelial function, arterial stiffness, and blood pressure in sedentary patients.
Cheng and MacDonald (2019) reported that research suggested that acute and chronic heat therapy (sauna, steam, and hot bath) may help improve arterial health and function.
Heat therapy improved microvascular function (microvessels are tiny blood vessels such as arterioles, venules, and capillaries).
Ukai and associates (2020) reported that hot baths may prevent cardiovascular diseases by improving blood flow or circulation (hemodynamic function).
The researchers investigated the long-term effects of hot baths on cardiovascular disease (CVD) risk. The study involved 30076 participants (40-59 years) with no previous cardiovascular disease and cancer histories.
The authors followed up the participants from 1990 until 2009. They grouped them according to the frequency of hot bathing sessions: 0-2 hot baths/week; 3-4 hot baths/week; more than 4 hot baths/week.
They collected data about the incidence of cardiovascular diseases among the participants from 1990 to 2009. They concluded that the frequency of hot bathing was inversely associated with the risk of CVD.
In other words, frequent hot bathing appeared to reduce the risk of CVD.
7. Heat therapy may act as an anti-depressant
Janssen and colleagues (2016) suggested that heat therapy may play a role in alleviating the symptoms of major depressive disorder.
They noted that previous studies found that a single session of heat therapy alleviated depression symptoms.
The team designed a 6-week randomized, double-blind study to test the suggestion that heat therapy had anti-depressant effects. The study involved 338 patients (aged 18 to 65) who met the criteria for major depressive disorder.
The authors reported that the group that received heat therapy showed a significant reduction in depression symptoms measured on the Hamilton Depression Rating Scale.
They concluded that heat therapy was safe and effective for treating depression and may have a prolonged therapeutic benefit.
8. Reduced risk of neurodegenerative conditions
Laukkanen and colleagues (2017) investigated the effect of sauna bathing on the risk of developing age-related neurodegenerative diseases, such as dementia and Alzheimer’s disease.
The study involved 204 patients with dementia and 123 with Alzheimer’s disease.
The researchers analyzed data adjusted for several health factors. The health factors included age, alcohol use, BMI, blood pressure, smoking, diabetes, and previous myocardial infarction.
They concluded that frequent passive heating exposure was associated with a lower risk of dementia and Alzheimer’s.
However, they recommended more studies to determine how sauna helped to reduce dementia and Alzheimer’s risk.
9. Role in managing type 2 diabetes
Hooper (1999) proposed that partial immersion of subjects in a hot tub may simulate the effects of physical exercise. He argued that since exercise was an effective therapy for type 2 diabetes, hot tubs may also have health effects that mimic exercise.
Hooper and his assistants asked eight patients — 5 men and three women aged 43 to 68 — to sit in a hot tub up to their shoulders.
The patient sat in the hot tub (37.8°C to 41.0°C) for 30 minutes, 6 days a week for 3 weeks. During the trial, they continued on the diet, exercise, and treatment regime they had previously received.
Hooper reported the following observations during the treatment period:
- The patients’ mean weight decreased by 1.7±2.7 kg
- Fasting plasma glucose decreased significantly from 182±37 mg per deciliter (10.1±2.0 mmol per liter) to 159±42 mg per deciliter (8.8±2.3 mmol per liter)
- After 10 days of heat therapy, one patient had to have their insulin doses reduced by 18 percent to prevent hypoglycemic reactions (low blood sugar)
- The patients reported improved sleep
- They also reported improvement in the general sense of wellbeing
Hooper suggested that based on the results of their trial, further studies were needed to assess the effectiveness of hot-tub therapy for managing type 2 diabetes.
10. Cardiometabolic health benefits of sauna exposure
Sauna may lower the risk of cardiometabolic syndrome and cardiometabolic disease (CMD).
Henderson and associates (2021) reported that individuals exposed to chronic stressors have an increased risk of cardiometabolic syndrome and cardiometabolic disease (CMD).
The stressors include poor nutrition, sleep deprivation, and psychological stress.
Cardiometabolic syndrome includes high blood pressure, insulin resistance, overweight/obesity, and atherosclerosis.
People exposed to chronic stressors, especially people in high-stress occupations, such as first responders, firefighters, police officers, and the military, have an increased risk of CMD.
Henderson and associates (2021) investigated the mechanisms by which acute and chronic sauna bathing may affect the markers of CMD.
The authors concluded that heat stress associated with sauna therapy is a hormetic stressor at the cellular level.
According to Henderson and associates (2021), passive heating is a potentially effective alternative intervention for cardiometabolic disease.
Cryotherapy (cold therapy) also has health benefits for people with cardiometabolic syndrome.
A study found that whole-body cryotherapy reduced belly fat in women with cardiometabolic disease.
11. Sauna use may extend healthspan
Healthspan is the proportion of a person’s total lifespan during which they are in good health.
According to Patrick and Johnson (2021), there was a growing body of observational, interventional, and mechanistic evidence that sauna bathing may increase healthspan.
Sauna bathing increases healthspan by improving cardiorespiratory health and protecting against neurodegenerative disease.
It may also help preserve muscle mass and counter sarcopenia in older adults.
The authors reported that evidence from large, prospective, population-based cohort studies suggested a positive dose-dependent relationship between sauna use and reduced morbidity and mortality.
That is, frequent use of the sauna was associated with improved healthspan.
Patrick and Johnson (2021) reported that the health benefits of sauna use were due to the ability to simulate the physiological responses to exercise and optimize stress responses through hormesis.
The authors noted that passive heating induces mild hyperthermia and triggers thermoregulatory responses that involve neuroendocrine, cardiovascular, and cytoprotective (cell protective) mechanisms that work synergistically to maintain homeostasis.
The homeostatic mechanism helps acclimate the body to heat and optimizes the response to future exposures.
12. Sauna bathing reduces risk of respiratory diseases
Kunutsor and colleagues (2017) reported that sauna bathing has many health benefits, including a reduced risk of respiratory diseases.
The researchers conducted a study to determine the relationship between the frequency of sauna bathing and the risk of respiratory diseases, such as pneumonia, chronic obstructive pulmonary disease, and asthma.
The study involved 1935 males (caucasian) aged 42-61 years. The participants recorded a total of 379 diagnoses of respiratory diseases during a follow-up period of 25.6 years (median value).
After adjusting for multiple risk factors, the authors found a positive association between the frequency of sauna baths and the risk of acute and chronic respiratory illnesses.
Kikuchi and associates (2014) conducted a study to evaluate the health effects of repeated waon therapy (Japanese term for sauna heat therapy) on patients with chronic obstructive pulmonary disease (COPD) (see also Umehara et al., 2008; Cox et al., 1989).
The study assigned a group of COPD patients (n=10) to waon therapy and conventional therapy with medications. Another group of 10 patients received only conventional therapy with medication (β2 agonists and anticholinergics) and pulmonary rehabilitation therapy.
The researchers exposed the waon therapy group to 15-minute sauna sessions at a temperature of 60°C once a day, five days a week for four weeks (a total of 20 sessions).
They assessed pulmonary function after four weeks and found a significant improvement in the waon therapy group compared with the control group.
The authors concluded that waon therapy could play an adjuvant role in the conventional treatment of COPD patients.
13. Promotes growth hormone release
Sauna therapy stimulates growth hormone release. The degree of stimulation depends on the frequency of exposure, duration, and temperature.
A study found that two 20-minute sauna sessions (80 °C/176 °F) with 30 minutes of cooling between sessions increased growth hormone secretion two-fold. However, two 15-minute sessions (100 °C/212 °F) with a 30-minute cooling period between sessions increased growth hormone production five-old (Patrick and Johnson, 2021; Hannuksela and Ellahham, 2001; Kukkonen-Harjula and associates (1989).
Repeated exposure to sauna also further boosted growth hormone production.
Sauna may prevent the loss of muscle mass (Ihsan and associates, 2020).
14. Sauna may relieve lower back pain
Cho and colleagues (2019) investigated whether dry sauna therapy relieved lower back pain.
The study involved 37 patients who had suffered lower back pain for up to two decades. They received 5 minutes of dry sauna therapy at 90°C for 5 consecutive days, twice daily for 15 minutes.
The researchers asked the participants to assess the effect of sauna exposure on their back pain. They rated the responses on the verbal numerical rating scale (VNRS) and the Oswestry disability index (ODI).
According to the researchers, the results showed that dry sauna exposure significantly reduced the measures of pain. Median pain scores on the VNRS decreased from 5 (before sauna) to 3 (after sauna). The median score on the ODI scale decreased from 12 (before sauna) to 8 (after dry sauna therapy).
Masuda and colleagues (2005) reported that passive heating relieved pain and improved outcomes in patients with chronic pain.
The study involved 22 hospitalized patients undergoing multidisciplinary treatment for chronic pain. The treatment combined infrared ray sauna therapy, cognitive behavioral therapy, rehabilitation, and exercise therapy.
The subjects received infrared sauna therapy daily for 4 weeks during hospitalization.
The control group included 24 patients with chronic back pain undergoing multidisciplinary treatment (cognitive behavioral therapy, rehabilitation, and exercise therapy) without sauna therapy.
The authors measured the participants’ subjective assessment of their symptoms using the visual analog scale (VAS) and other rating tools such as the depression scale and anger score.
A comparison of the scores before and after heat therapy, and outcomes 2 years after discharge from the hospital, suggested significant improvement due to heat therapy.
Sauna heat may relieve pain partly by improving circulation and partly by inducing muscle relaxation.
Other therapies claimed to reduce body aches and pain include pressure point or acupressure therapy.
15. Heat therapy promotes physical fitness
Patrick and Johnson (2021) reported that sauna improved physical fitness by improving cardiorespiratory health, endurance, and muscle mass.
According to the authors, sauna heat has a positive effect on the components of physical fitness, such as:
- Cardiorespiratory fitness
- Musculoskeletal strength
- Body composition (such as lean mass or fat percent)
Scoon and associates (2007) found that sauna use improved endurance in male distance runners.
They found that a 30-minute post-training sauna session twice a week for 3 weeks significantly increased the time it took for the athletes to run to exhaustion by 32%.
The authors suggested that increased endurance could be due to the subjects’ physiological adaptation to heat stress during sauna bathing.
Other studies found that passive heating improved performance during endurance exercise by improving heat tolerance and efficiency of thermoregulatory mechanisms.
16. Sweating and excretion of heavy metals
Multiple studies found significant levels of heavy metals in sweat and concluded that sweating may play a role in the excretion of toxic heavy metals (Patrick and Johnson, 2021).
However, the subject remains controversial, with some medical experts pushing back against seemingly exaggerated claims that sauna sweating detoxifies the system.
Patrick and Johnson (2021) reported that studies found that sweating may play a role in the excretion of toxic heavy metals.
Citing Genuis and colleagues (2011), Patrick and Johnson (2021) noted that toxic heavy metals have been detected in sweat at higher concentrations than in urine:
- Aluminum: 3.75-fold
- Cadmium (25-fold)
- Cobalt (7-fold)
- Lead (17-fold)
Sears and associates (2012) conducted a systematic review of scientific literature about arsenic, cadmium, lead, and mercury levels in sweat. According to the authors, studies showed that individuals with high exposure to heavy metals had higher concentrations in sweat than in urine and plasma.
In arsenic-exposed individuals, dermal (skin) excretion was seven-fold higher than in unexposed individuals, while cadmium levels were generally higher in sweat than in blood plasma.
The authors cited a study that reported higher lead levels in sweat collected after endurance exercise (such as long-distance jogging) than intensive exercise (100m sprint).
But most significantly, the researchers noted that mercury levels in sweat normalized with repeated sauna exposure.
Based on these results, the authors suggested that sweating may play a role in toxic element detoxification.
“Sweating offers potential and deserves consideration, to assist with removal of toxic elements from the body,” the authors wrote.
They recommended studies to assess the role that sweating may play in improving health outcomes for individuals with high exposure to toxic heavy metals.
In a recent study, Kuan and associates (2022) noted that physiologists have long believed sweating could play a role in heavy metal detoxification.
The authors reported that dynamic exercise (such as running on a treadmill) was more effective for the excretion of heavy metals than passive heating in a sauna.
The team investigated the levels of heavy metals, such as nickel (Ni), lead (Pb), copper (Cu), arsenic (As), and mercury (Hg) in sweat.
The study involved 12 healthy university students (males=6; female=6). They collected sweat samples
while the subjects performed various exercises and also while resting in a sauna.
Analysis of the samples revealed that sweat contained significant levels of heavy metals. Concentrations of nickel (Ni), lead (Pb), copper (Cu), and arsenic (As) were significantly higher in sweat samples collected during dynamic exercise than during sauna sessions.
[Note: Dynamic exercise involves movement through rhythmic muscle activity.]
However, the concentration of mercury (Hg) in sweat did not appear to be affected by the sweating method.
They concluded that dynamic exercise was more effective for the excretion of heavy metals from the body than sauna exposure.
17. Sauna and skin diseases
Hannuksela and Väänänen (1988) reported that sauna heat kills dermatophytes (pathogenic fungi that grow on the skin) and microbes that cause skin infection.
Sauna bathing also facilitates the elimination of hyperkeratotic scales associated with psoriasis.
But the authors noted that dry sauna-induced sweating causes intense itching in some people with atopic dermatitis. It may also cause cholinergic urticaria in susceptible individuals.