THE TOP SCIENCE-BACKED BENEFITS OF SAUNAS
Hormesis – The Good Stress
A study out of Finland followed 2,315 men (aged 42-60) for 20 years (studies this long are very rare) and found that those using the sauna 2-3 times per week (as opposed to just one time per week) were a whopping 24% less likely to die from all causes. But there’s even more – the effects continued to increase the more one used the sauna. Those using the sauna 4-7 times per week were an amazing 40% less likely to die from all causes.
One of the mechanisms for this may be the activation of heat shock proteins (HSPs). Aging is associated with a progressive accumulation of molecular damage and reduced cellular defense mechanisms. HSPs can repair damaged cells, promote autophagy (the recycling of damaged cell parts) and also prevent future damage by scavenging free radicals and increasing antioxidant capacity through the maintenance of glutathione, a master antioxidant.
Higher levels of HSPs have been linked to longevity, as women with a gene polymorphism that leads to increased expression of HSPs live longer.
Heat stress also activates FOXO3, which has been called the longevity gene since polymorphisms in this gene are associated with the ability to attain exceptional old age. FOXO3 affects the expression of a number of other genes, such as those involved in DNA repair and cell death, immune function, stress resistance, autophagy, tumor suppression, and the activation of stem cells. These are all critical functions that decline as we age, so a robust activation of FOXO3 via sauna use is a powerful anti-aging strategy!
Heat stress is a powerful type of hormesis, and heat shock proteins (that special type of proteins that are strongly elevated in response to heat exposure) play a big role in improving mitochondrial health and function.
Why is that important?
Simple: Mitochondria are the energy generators in our cells, and our energy/vitality depend directly on their size, power, number, and function.
If your mitochondria are damaged, weak, small, fragile, and unhealthy, then you will be too. Moreover, a huge body of emerging research is now pointing to mitochondrial health/function as a major root cause of dozens of chronic diseases and even aging itself. While there are only a few studies testing this directly, heat stress has been shown to induce profound changes in mitochondrial health.
Saunas may also be the single most powerful tool we have for detoxification from environmental chemicals and heavy metals. Sauna use shows real promise for detoxification from heavy metals, PCBs, PBBs, BPA, drugs, and organochlorine pesticides such as DDT (which has been banned for decades but is still ubiquitous).
Many toxicants have long half-lives and bioaccumulate up the food chain, so even if you are avoiding new exposures to the extent possible by cleaning up your immediate environment and being careful about household and personal care products, no one can avoid all exposures and most people likely already have significant stores of toxicants. In our current world, even newborn babies have already been exposed, as a total of 287 toxic chemicals were identified in umbilical cords in a recent study.
In short, even if you’re a health-conscious person who goes out of your way to avoid environmental toxicants, it’s still a safe bet that your body has accumulated some significant burden of nasty chemicals and heavy metals. (And if you haven’t been a health-conscious person who is aware of how to avoid such chemicals, then it’s a safe bet that you have a fairly high body load of accumulated toxicants.) Thus ongoing detoxification is very important.
Cardiovascular disease is the leading cause of death worldwide.
Sauna bathing is inversely associated with the risk of sudden cardiac death, coronary heart disease (CHD), and cardiovascular disease (CVD) independent of conventional risk factors. A Finnish study (mentioned above) following 2,315 men for 20 years found that the risk of fatal CHD events was 23% lower for 2-3 sauna sessions per week and 48% lower for 4-7 times per week. Risk of dying from cardiovascular disease was 27% in the group using the sauna 2-3 times per week, and a whopping 50% lower for those using the sauna 4-7 times per week.
Another study following 2,227 men for 26 years found that sauna use was associated with lower risk of cardiovascular mortality independent of cardiorespiratory fitness. That means the sauna was conferring benefits above and beyond exercise alone. The authors concluded that the combination of the two may confer additional survival benefits since those who had high cardiorespiratory fitness and high sauna use (3-7 times per week) had the lowest CVD and all-cause mortality. After adjusting for age, BMI, smoking status, Type II diabetes, cholesterol, current CHD, alcohol consumption, socioeconomic status, and C-reactive protein levels, those with high cardiorespiratory fitness and high sauna use had a 58% lower risk of CVD mortality and a 40% lower risk of all-cause mortality. Adjusted for age alone, the reduction in risk was 73% and 55%, respectively.
Research has shown that sauna use in combination with exercise is more effective at lowering blood pressure than exercise alone.
For high blood pressure, even sauna bathing as little as every other week had benefit. A group of hypertensive men using the sauna every two weeks for three months experienced a drop in blood pressure equivalent to that caused by hypertensive medications.
Researchers in Finland studied more than 1,600 middle-aged men and found that those who took sauna baths four to seven times a week lowered their risk of high blood pressure by nearly 50% (compared to those using the sauna only once per week).
In one study, people participated in either 15 minutes of exercise followed by 30 minutes of infrared sauna, or 15 minutes of exercise only (the control group). Participants in the sauna group lost 1.8 times as much weight and 4.6 times as much body fat as controls. Adding to this, we also have other lines of evidence suggesting a link between HSPs and fat loss. Mice with high expression of HSPs have lower body fat mass, better insulin tolerance and glucose clearance, less intramuscular lipid accumulation, more oxidative enzymes and higher number of mitochondria.
How Saunas Help With Weight Loss
Sauna use can also modulate appetite. In one study, normal-weight patients with appetite loss increased ghrelin (a hormone associated with hunger) concentrations, leading to normal daily caloric intake and feeding behavior. Obese patients, on the other hand, did not have an increase in ghrelin and instead, using the sauna reduced “abnormal feeding behavior” such as overeating and snacking between meals. Their body weight and body fat significantly decreased after two weeks of sauna therapy. Sauna uses increases metabolic rate and oxygen consumption similar to moderate exercise. This may help with weight maintenance for those unable to exercise due to illness or injury. Thus, there are likely multiple mechanisms at play in why saunas promote fat loss.
Sauna use can increase endurance. In one study, male distance runners using the sauna for 30 minutes post-workout for just three weeks increased their run time to exhaustion by a whopping 32%!
How Saunas Improve Physical Performance
Cardiovascular improvements gained via hyperthermic conditioning – like increased plasma volume, increased red blood cells and blood flow to the heart – improve athletic endurance and performance. These benefits apply to athletes at all levels: highly trained, moderately trained, and untrained. Hyperthermic conditioning improves thermoregulatory mechanisms, which means your body stays cooler and performs better at higher temperatures, like those induced during exercise. Increased blood flow to skeletal muscles improves nutrient delivery, reducing reliance on glycogen stores during exercise. One study noted that heat acclimation reduced glycogen depletion during exercise by 40-50%. In other words, sauna use seems to help the body perform exercise more efficiently and with greater ease. The effects on performance have led some to call sauna use a “performance enhancing drug.”
Sauna use increases muscle growth (hypertrophy) and reduces muscle breakdown.
HSPs repair damaged cells and help prevent future damage by reducing oxidative stress, which is a major cause of muscle degradation. This results in reduced muscle breakdown.
Why Increased Muscle Growth Is One Of The Many Health Benefits of Saunas
Sauna use causes a major increase in growth hormone levels. Depending on the temperature, duration, and frequency of sauna exposure, these increases are generally between 2- and 5-fold, but one study showed that after two one-hour sessions per day at 80°C (176°F) for seven days, growth hormone levels increased 16-fold on the third day! Growth hormone increases levels of insulin-like growth factor I (IGF-1), which increases protein synthesis and decreases protein breakdown, resulting in muscle hypertrophy. Studies in rats have shown that heat treatment reduces oxidative stress and protects muscle mass (reduces atrophy) during immobilization and enhances muscle regrowth and reduces oxidative stress during regrowth. In one study this resulted in a 30% increase in muscle regrowth compared to mice not exposed to heat.
Lactic acid build-up in the muscles after exercise is reduced as the result of hyperthermic conditioning. Sauna use reduces exercise-induced muscle damage and delayed-onset muscle soreness. Researchers have found that infrared heat improves recovery of the neuromuscular system after maximal endurance performance.
How Saunas Speed Up Post-Workout Recovery
As mentioned above, sauna use enhances muscle regrowth and reduces oxidative stress after a period of immobilization. So don’t forget to make the sauna part of any injury recovery! HSPs may protect against rhabdomyolysis, a serious condition caused by excessive muscle breakdown due to overuse which can cause kidney failure. Hyperthermic conditioning leads to higher expression of HSPs under both normal conditions and subsequent exposure to heat, so pre-conditioning is key here. Sauna use is a potent tool for accelerates recovery in between exercise sessions.
Sauna use also increases brain-derived neurotrophic factor (BDNF). It increases neuroplasticity, which is important for learning and long-term memory. Importantly, low BDNF has been linked with both depression and chronic fatigue syndrome (CFS). Other research has shown that sauna use has a huge impact on other hormones like norepinephrine and prolactin, which play roles in focus and attention, as well as promotes nerve myelin growth and nerve repair.
How Saunas Improve Brain Performance, Neuron Repair, and Growth of New Brain Cells
Sauna use significantly increases norepinephrine and prolactin levels, which has benefits for mental performance. During sauna, norepinephrine increases 2- to 4-fold, while prolactin increases from 2- to 10-fold. Norepinephrine improves focus and attention. Heat stress also increases the capacity of norepinephrine to be stored for later use. Prolactin promotes myelin growth. Myelin insulates nerve fibers and increases the speed at which nerve impulses are conducted, which makes your brain work faster. It is also important for repairing nerve cell damage. In addition, the “runner’s high” – the sense of euphoria that accompanies prolonged exercise – is thought to be related to heat stress, and research has shown that sauna use affects these same endorphin pathways.
Passive heat therapy improves skin microvascular function, which means better nutrient delivery to skin cells.
How Saunas Improve Skin Health
Mild heat stress has anti-aging hormetic effects on the growth of human skin fibroblasts (cells in connective tissue that produce collagen and other fibers). In other words, it temporarily stresses your skin cells and induces them to build up their anti-oxidant defense systems and stimulating cell repair processes, which protect them from future stresses (like sun exposure or toxins). Regular sauna use has a beneficial effect on skin health, improving hydration, maintaining surface pH, and resulting in less oil on the forehead of participants measured. Sauna may benefit people with psoriasis because it aids the removal of scales. In short, sauna use is a powerful tool for improving your skin health.
Sauna use also increases red blood cell count, which means greater oxygen delivery to muscles. Greater capacity to deliver oxygen to your cells means better energy, as well as better brain performance and physical performance. You may remember back to the Tour de France scandals involving competitors injecting their own stored blood (that had been removed weeks prior) to increase red blood cells, and injecting erythropoietin (EPO) to stimulate their body to produce more red blood cells. (Note: Athletes often train at altitude to stimulate some of these benefits as well).
How Saunas Improve Oxygen Delivery
Well, it turns out that sauna use mimics many of these effects and can also boost EPO and red blood cell count. This is likely because the body increases plasma volume (the overall amount of fluid in your blood vessels) – likely as a way to adapt to sweating so much – and then the body increases red blood cells to keep the concentration of red blood cells to plasma optimal. The end effect of increased red blood cells is that saunas don’t make you better at tolerating heat – they actually help your stamina, endurance, performance (physical and brain performance), perceived exertion during exercise, and overall energy levels.
Fibromyalgia patients receiving thermal therapy combining sauna and underwater exercise reported 31-77% reductions in pain and symptoms after the 12-week program. These improvements continued throughout the 6-month follow-up period, which also noted also an improved quality of life.
Why Saunas Decrease Pain and Fibromyalgia Symptoms
Regular sauna use has also been found to reduce headache pain intensity in those suffering from chronic tension-type headaches (CTTH).
In people with leg pain from peripheral artery disease (PAD) – a common form of cardiovascular disease where plaque builds up in the arteries and hinders blood flow, causing pain while walking – researchers found that 6 weeks of daily 15-minute sauna sessions caused a nearly 70% reduction in pain (compared to no change in pain in the control group that didn’t use a sauna)! In addition, the group that used the sauna was able to walk twice as far without pain, compared to the control group which had no change in walking distance.
Researchers in Japan studied the effects of infrared (Waon) sauna sessions in 13 women with fibromyalgia. They were given infrared sauna therapy (at 140°F) for 15 minutes either two or five days per week. Following the sauna, they laid down in a warm room and were covered with a blanket for another 30 minutes. Pain was reduced by nearly half following just the first session (but this pain-killing effect only lasted for a few days initially). However, the effect became persistent and lasting following about ten treatments, at which point, the women reported pain reductions between 20%-78%! Again, that is after just ten 15-minute sauna sessions, which was completed in just 2-5 weeks of sauna use.
Inflammation has been implicated in almost every major disease. Although inflammation results from the attempt of the body to heal itself, chronic systemic inflammation can form a negative feedback loop that can prevent or delay healing. Reducing inflammation is critical for health. Chronic inflammation is also a major cause of chronic fatigue. HSPs play a role as an anti-inflammatory protein, suggesting that sauna use may have benefits for chronic inflammation. Indeed research confirms that it does have benefits.
Participants engaged in daily infrared sauna therapy for two weeks had lower markers of oxidative stress, which can lead to inflammation. Using the sauna is associated with lower levels of C-reactive protein (CRP), an important marker of systemic inflammation. Men in a study who used the sauna 2-3 times per week had 17% lower levels of CRP and those using the sauna 4-7 times per week had 32% lower levels of CRP compared to those only using it once per week. (And we don’t know how much higher the levels were for those not using the sauna at all!)
Heat stress bolsters the immune system. Part of the mechanism for this is that HSPs stimulate both innate and adaptive immunity.
How Saunas Improve Immune Function
Regular exposure to sauna can reduce the incidence of the common cold. In one study, half of the participants engaged in sauna use once or twice per week while the other half did not. The incidence of the common cold was similar for the first three months of the study, but in the second three months, the sauna group had less than half the number of colds. High sauna temperatures easily kill infectious microbes on the skin, which can be beneficial for skin infections of many kinds. Many practitioners swear by the effectiveness of sauna use for hard-to-treat chronic infections.
Evidence suggests that hyperthermia can cause apoptosis, or cell death, in both normal and tumor cells, but the damage caused by hyperthermia is not evident in normal cells. This might be due to what has been called (in the context of fasting) “differential stress resistance,” in which our own cells can adapt to stress but cancer cells cannot.
How Saunas Can Help Prevent Certain Types of Cancer
The FOX family proteins (such as FOXO3) play a critical role in tumor suppression. Since we know that sauna use affects FOXO3, it is reasonable to suspect there may be a link here. Cells with high acidity and low pH such as cancer tumor tissues are more susceptible to heat due to insufficient blood flow. Meanwhile, the effectiveness of radiation and some types of chemotherapy are enhanced by heat. Therefore, in many cancer treatments, the addition of hyperthermia results in an additive effect. Hyperthermia alone (local, regional, or whole-body) has shown complete response rates of 13% in several cancers, and clinical trials adding hyperthermia to radiation and/or chemotherapy have resulted in as much as a 50% improvement in response rates, tumor control, and overall survival. The addition of hyperthermia to other treatments has shown significantly improved outcome in cancers of the head and neck, breast, brain, bladder, cervix, rectum, lung, esophagus, vulva and vagina, and also for melanoma. Hyperthermia induces cell death in melanoma and non-melanoma skin cancer cells.
The accumulation of misfolded proteins in the brain is thought to play a critical role in the development of many neurodegenerative conditions, such as Alzheimer’s. Research suggests that elevating HSPs and FOXO3 (e.g. via sauna use) may activate the repair of misfolded proteins, restoring their proper structure. This can prevent them from clumping together and forming plaques, which have been implicated in both Alzheimer’s and cardiovascular disease.
How Saunas Fight Neurological Diseases Like Alzheimer’s and Dementia
A Finnish study that followed 2,315 men for 20 years found that those who used the sauna 2-3 times per week (compared to only once per week) had a 22% and 20% risk reduction of dementia and Alzheimer’s disease, respectively. Importantly, this was after adjusting for age, alcohol consumption, BMI, blood pressure, smoking status, exercise habits, Type 2 diabetes, previous heart attack, resting heart rate, and cholesterol levels. This is important in this type of long-term observational study so that we know that these results are not confounded by a person’s other lifestyle habits or health history. But here’s the even more impressive part: Those who used the sauna 4-7 times per week had a 66% reduced risk of dementia and a 65% reduced risk of Alzheimer’s disease compared to those who only used the sauna once per week!
A large observational study found that those who used the sauna 4 or more times per week had a 41% lower risk of respiratory diseases over a 26-year follow-up period than those who used the sauna less than once per week. Those who used the sauna 2-3 times per week had a 27% lower risk. Sauna use decreases lung congestion, and increases the vital capacity, tidal volume, minute ventilation, and forced an expiratory volume of the lungs. Patients with asthma or chronic bronchitis report that sauna improves their breathing. Patients with obstructive lung disease experienced improved lung function with sauna use. It is possible that the hot air of the sauna may initiate a hormetic response in the lung tissues and help stimulate cell repair and build up the internal antioxidant defense systems of the lung cells, thus protecting them from damage from a broad range of stressors.
Sauna use has been shown to combat depression in numerous ways. Depression has been linked in numerous studies to elevated core body temperature. the Research shows that, counterintuitively, giving people with depression a brief hit of even higher body temperature (e.g. via sauna use or other body heating devices) can lead to remarkable improvement in depression.
How Sauna Use Act As An Anti-Depressant and Fights Depression
- Temporarily increasing body temperature and spiking inflammation (and increasing heat-shock proteins) actually lowers baseline body temperature and inflammation (normalizes body temperature regulation and inflammatory/immune pathways), through hormesis.
- Heat hormesis also may promote autophagy in the brain, which makes brain cells more resilient and resistant to a range of stressors.
- Sauna use has been shown to cause a massive release of beta-endorphins in the brain, leading to better mood and fewer negative effects of stress.
- Heat acclimation also has the longer-term effect of making you more sensitive to endorphins. When the body is under heat stress, a substance called dynorphin is released. Dynorphin has a role in thermal regulation but it also produces dysphoria or discomfort. To counter this, the body responds by not only producing more endorphins but more endorphin receptors and increasing the sensitivity of those receptors. This means you need less to feel good even when you are not heat-stressed, so you can get more pleasure from everyday activities, like watching a sunset.
Sauna use might help the treatment of autoimmune diseases such as Type 1 diabetes and rheumatoid arthritis. This is because certain HSPs can regulate the immune system, suppressing overactive responses in autoimmune diseases.
How Saunas May Help People With Autoimmune Diseases
In a case report, a woman with Sjogren’s syndrome underwent 20 sessions of infrared sauna treatment over the course of 4 weeks. She experienced “dramatic” improvements in dry mouth and arthritis and her antigen levels dropped into the normal range. Studies based on interviews of approximately 200 patients with rheumatoid arthritis have found that 40% to 70% experience alleviated pain and improved joint mobility with sauna use. However, approximately half of the patients temporarily experience worse pain the following day before seeing the improvements in symptoms. Many reported that this could be prevented by a cool shower after the sauna.
Reduction in HSPs has been shown in individuals with Type 2 diabetes and correlates with insulin resistance and glucose control
How Saunas Improve Insulin Sensitivity and Help Combat Diabetes
Researchers have suggested that therapies utilizing HSPs might serve as a treatment tool for Type 2 diabetes and metabolic diseases.
FOXO increases insulin sensitivity by inducing expression of the insulin receptor. Diabetic mice exposed to whole-body hyperthermia 3 times per week for 12 weeks had a 31% reduction in insulin levels and significantly decreased fasting blood glucose levels. The ability of hyperthermia to increase insulin sensitivity was further established in glucose tolerance tests and insulin tolerance tests. Increasing physical activity has a beneficial effect on metabolic health, but sometimes people who would benefit most are unable to do it due to medical conditions or disability. Sauna use cannot replace all the benefits of exercise, but it may replicate some of the benefits and alleviate some of the symptoms associated with Type 2 diabetes.
In a case report, two CFS patients received infrared sauna therapy (Waon therapy) once a day for 35 days, and then once or twice per week thereafter for one year. They experienced improvements in physical and mental complaints, fatigue, depression, confusion, and sleep. Energy levels and hours of non-sedentary activity increased. Both patients were able to return to work 6 months after beginning therapy.
How Sauna Use Helps Combat Symptoms of Chronic Fatigue Syndrome (CFS/ME)
A pilot study found that sauna use (Waon therapy) improved cerebral blood flow and brain function in all 11 participants with CFS. This correlated with self-rated improvements in CFS symptoms. Another study found that perceived fatigue, anxiety, depression, and performance status improved in patients with CFS following 4 weeks of Waon therapy.