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Whole-body hyperthermia featured article

Hyperthermia, a state of elevated core body temperature, stresses the body, activating molecular mechanisms that mitigate protein damage and aggregation and promote endogenous antioxidant, repair, and degradation processes. Whole-body hyperthermia is a therapeutic strategy used to treat various medical conditions, including cancer, fibromyalgia, and others. Emerging evidence suggests that whole-body hyperthermia might be useful in treating depression.

While similar conceptually to recreational sauna use, whole-body hyperthermia may differ in that the nature of the duration and temperature of clinical interventions specifically targets levels of functional stress that drive key physiological responses, such as protein denaturation, alteration of cellular structures (such as the cytoskeleton and membranes), and changes in enzyme complexes needed for DNA synthesis and repair.

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Q&A #69 with Dr. Rhonda Patrick (4/5/25)

Posted on April 28th 2025 (about 2 months)

Dr. Rhonda Patrick covers lithium microdosing, reducing homocysteine, aluminum's link to cancer, and beta-alanine and alpha-lipoic acid supplements.

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The Biggest Benefit of Saunas No One Is Talking About

Posted on April 1st 2025 (3 months)

In this clip, Dr. Rhonda Patrick and Brady Holmer discuss how sauna use enhances fitness, supports muscle health, and boosts longevity.

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Q&A #67 with Dr. Rhonda Patrick (2/8/25)

Posted on February 18th 2025 (4 months)

Dr. Rhonda Patrick discusses microdosing nicotine, GlyNac benefits, intermittent fasting and hair loss, and cold & flu relief.

Topic Pages

  • Sauna

    A sauna is an enclosed, heated, low-humidity environment elevating core temperature and provoking vasodilatory, sudomotor, and cardiovascular thermoregulatory responses.

  • Whole-body hyperthermia

    Sauna exposure passively induces whole-body hyperthermia via convective and radiant heating, elevating core temperature and thermoregulatory responses.

News & Publications

  • Regular infrared sauna use increases blood vessel density in aged muscles by 33%, though muscle size, strength, and protein synthesis remain unchanged. pubmed.ncbi.nlm.nih.gov
    Aging Heat Stress Muscle Sauna Protein

    Scientists have speculated that regular heat exposure, such as that experienced in a sauna, might help aging muscles adapt in ways that preserve strength and mass. A recent study found that older adults who engaged in infrared sauna sessions regularly experienced a 33% increase in the number of small blood vessels surrounding their muscle fibers.

    Researchers asked 14 healthy older adults (65 to 85 years old) to sit in an infrared sauna (60°C, 140°F) for 45 minutes, three times weekly, for eight weeks. They collected muscle biopsies before and after the heat exposure to measure capillarization—the number of capillaries around each muscle fiber—as well as muscle size. They also tracked muscle protein synthesis using amino acid infusions and ultrasound imaging to assess how well blood flowed through muscle tissue after eating. Finally, they measured leg strength using a one-repetition maximum test.

    After eight weeks of heat therapy, participants had 31% to 33% more capillaries surrounding both type I and type II muscle fibers. However, muscle blood flow, protein synthesis rates, leg strength, and muscle size did not improve. Body weight, body composition, and walking speed also stayed the same. The only physical performance measure that improved was handgrip strength, which increased slightly. Interestingly, systolic blood pressure dropped by 2%, while diastolic pressure and resting heart rate were unchanged.

    These findings suggest that passive heat treatment can increase blood vessel density in older muscle tissue, but this change alone doesn’t improve nutrient delivery, muscle building, or strength. Heat exposure might support muscle health in other ways, but it doesn’t appear to be a replacement for resistance or aerobic exercise. Learn more about the benefits of heat exposure in Aliquot #96: Thermal Stress, Part I: The Science Behind Heat Stress and its Positive Effects on Health.

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  • Post-exercise hot tubs and saunas show minimal, inconsistent benefits in exercise performance enhancement, despite potential physiological effects. bmcsportsscimedrehabil.biomedcentral.com
    Exercise Heat Stress Sauna

    Training in hot conditions can drive marked improvements in endurance by triggering cardiovascular and thermoregulatory adaptations. However, access to heat training chambers is limited, and the physical demands of exercising in high temperatures can be risky or impractical. A recent study found that sitting in a sauna or soaking in hot water after exercise—a practice known as “passive heat acclimation"—might offer some of the same benefits as working out in the heat, but the evidence was weak and inconsistent.

    Researchers reviewed 10 studies involving nearly 200 healthy adults, comparing those who used post-exercise heat exposure via sauna or hot water immersion to those who did not. All participants completed similar exercise training programs, and the researchers analyzed outcomes related to performance in hot or neutral conditions, aerobic capacity, heart rate, body temperature, sweat response, and perceived exertion.

    The analysis revealed little to no improvement in performance for those using passive heat acclimation, identifying only a 4% difference between groups—an effect that was statistically weak and inconsistent across individuals. Heat exposure slightly improved maximum oxygen uptake, sweat rate, and thermal discomfort ratings. However, the overall certainty of the evidence was low to very low, due to small study sizes and inconsistent reporting.

    These findings suggest that while passive heat exposure may exert some physiological effects, its ability to improve exercise performance remains unclear. More rigorous, well-controlled trials are needed before recommending hot tubs or saunas as a reliable substitute for training in the heat. Learn more about heat exposure in this peer-reviewed article by Dr. Rhonda Patrick.

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  • Post-exercise infrared sauna use contributes to a 25% increase in jump height and a 6.8% peak power boost in female athletes—a potential tool for enhancing power production. pmc.ncbi.nlm.nih.gov
    Exercise Performance Muscle Sauna

    Infrared saunas are gaining in popularity among athletes as a recovery tool, but their effects on strength training adaptations remain uncertain. While traditional saunas can impair performance, infrared saunas may offer a more effective and comfortable recovery option. A recent study found that using infrared saunas after exercise enhances power production but doesn’t influence muscle growth.

    Forty female team sport athletes participated in the study, with half using an infrared sauna after training sessions for six weeks. Sauna sessions were done three times weekly for 10 minutes at 50°C (122°F) following their training. All participants underwent body composition measurements and physical performance tests, including sprint tests, jumps, and leg press exercises, before and after the training period.

    Both groups improved in neuromuscular performance and muscle size. However, the infrared sauna group showed greater jump height and peak power improvements, with a 25% increase in jump height and a 6.8% increase in peak power. Five-minute sprint times were also faster in the infrared sauna group, though not statistically significant. While both groups gained lean mass, the infrared sauna group experienced small body mass and fat mass increases. There were no marked differences between the groups in muscle hypertrophy or other body composition changes.

    These findings suggest that post-exercise infrared sauna use enhances power output over time but doesn’t affect muscle growth. Learn more about the benefits of infrared and traditional sauna use in our overview article.

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  • More than 3,600 food-contact chemicals used in packaging and storage detected in humans, including several toxic substances associated with cancer, fertility issues, and hormone disruption. www.nature.com
    Cancer Bisphenol A Pollution Sauna

    Despite the perceived safety of the U.S. food supply, many chemicals used in food packaging and storage may be hazardous. In fact, food scientists have found that more than 1,800 food-contact chemicals migrate into foods—many of which have never undergone toxicity testing. New research demonstrates that more than 3,600 of these toxic compounds have been detected in humans.

    Researchers compared a list of more than 14,000 known food-contact chemicals to five major biomonitoring programs and several databases that track chemicals in the human body. They then prioritized chemicals frequently found in food packaging and examined evidence for their presence in humans.

    They found that 3,601 of these chemicals have been detected in humans. Of these, 194 were identified in biomonitoring programs, 80 of which carry a high toxicity risk. They also confirmed that 63 of 175 chemicals of concern were present in the human body, and most lacked safety data.

    These findings suggest that human exposure to food-contact chemicals is widespread, highlighting the need for stricter safety regulations. Many food-contact chemicals include bisphenol A, phthalates, and other toxic substances that promote cancer, impair fertility, and disrupt hormone signaling. Although many of these compounds accumulate in the body over time, some are preferentially excreted in sweat. Learn how sauna use promotes sweating, helping the body rid itself of some toxic substances.

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  • Warming muscles prior to high-intensity exercise boosts power and performance by 11%, suggests a small study on cyclists. link.springer.com
    Exercise Heat Stress Cold Stress Sauna

    Study link:

    Athletes often warm up before a big race, but does heating your muscles make a difference? An early study found that warming muscles boosts performance by 11% during intense exercise—but at a cost.

    Researchers asked four young, healthy adults to perform 20-second high-intensity sprints on an exercise bike under four different muscle temperature conditions: room temperature, after leg immersion in hot water (44°C/111.2°F), and after immersion in cool water (18°C/64.4°F and 12°C/53.6°F). They measured the participants' muscle temperature and analyzed their peak force and power output during each sprint.

    They found that increasing muscle temperature using warm water immersion boosted peak force and power 11% more than resting at room temperature. In contrast, cooling the legs in 18°C (64.4°F) and 12°C (53.6°F) water decreased power output 12% and 21% more, respectively. However, higher muscle temperatures also led to quicker fatigue during the sprints. The beneficial effect of temperature was greater at higher pedaling speeds, with a 10% increase in power for every degree (1°C/1.8°F) increase in temperature at the fastest speed.

    It’s important to note that this was a small study that was conducted several years ago. However, the findings suggest that warming muscles before high-intensity exercise enhances power and performance, particularly at faster speeds. This benefit comes with a trade-off of earlier fatigue, potentially limiting endurance activity performance. Cooling, on the other hand, may reduce power output but could extend endurance by slowing the onset of fatigue.

    Interestingly, research shows that warming the body after exercise—in a sauna, for example—can boost performance. In contrast, cCooling the body after exercise may improve glucose and lipid metabolism, decrease inflammation, improve cognitive performance, and enhance immune function — possibly at the cost of reductions in hypertrophy. Learn more in this episode featuring Dr. Rhonda Patrick.

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  • Frequent sauna use reduces the risk of psychosis by 51 percent, regardless of fitness levels. www.sciencedirect.com
    Exercise Mental Health Sauna

    Psychosis is a neuropsychiatric condition characterized by a disconnection from reality, often manifesting as hallucinations or delusions. Evidence suggests that lifestyle factors reduce the risk of developing psychosis. A recent study found that using a sauna three or more times a week reduces the risk of psychosis by more than half, regardless of fitness levels.

    Researchers drew on data from the Kuopio Ischemic Heart Disease Risk Factor Study, an ongoing investigation of adult men living in Finland. The researchers assessed the men’s cardiorespiratory fitness and collected information about their weekly sauna use, categorized as low use (fewer than two sessions) or high use (three or more sessions). They identified participants who had been diagnosed with psychosis during a period of about 25 years.

    They found that cardiorespiratory fitness markedly reduced the risk of psychosis, with medium fitness reducing risk by 35 percent and high fitness reducing risk by 25 percent. However, they found that high sauna use reduced the risk of developing psychosis by 50 percent compared to low use, even when they took fitness levels into account.

    These findings suggest that frequent sauna use and medium to high cardiorespiratory fitness independently reduce the risk of psychosis. However, frequent sauna use might lower the risk of psychosis regardless of fitness levels and could be a stronger predictor of reduced psychosis risk than cardiorespiratory fitness.

    Sauna use exposes the body to extreme heat, stressing the body. Heat stress reduces systemic inflammation, oxidative stress, and cortisol levels, which may play roles in the development of psychosis. Learn more about the brain benefits of sauna use in this episode featuring Dr. Rhonda Patrick.

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  • Exposure to flame retardants in everyday household items increases the risk of cancer death more than fourfold. www.dailymail.co.uk
    Cancer Mortality Sauna

    Polybrominated diphenyl ethers (PBDEs) are flame retardants – a broad class of compounds commonly applied to fabrics, carpets, furniture, cell phones, and many other household items. New evidence suggests that exposure to flame retardants more than quadruples the risk of dying from cancer.

    Researchers analyzed blood samples from 1,100 adults enrolled in the National Health and Nutrition Examination Survey and tracked their health for about 16 years. They found that PBDE exposure markedly increased the risk of dying from cancer. Participants with the highest serum PBDE levels were more than four times more likely to die of cancer than those with the lowest levels, even after considering age, sex, race, ethnicity, lifestyle, and other factors that influence cancer death risk.

    These findings suggest that PBDE exposure increases the risk of dying from cancer. Although this observational study did not establish a cause-and-effect relationship between PBDEs and cancer risk, PBDEs are known endocrine disruptors. Endocrine disruptors mimic or interfere with normal hormonal processes in the human body and may influence health throughout the lifespan.

    Interestingly, evidence suggests that sweating promotes PBDE elimination. Sweat losses during a typical sauna session may reduce PBDE burden in the body, potentially reducing cancer death risk. Learn more about how sauna use facilitates the elimination of various toxicants in our overview article.

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  • Higher cardiorespiratory fitness mitigates high blood pressure risks, reducing cardiovascular disease-related death. www.sciencedaily.com
    Exercise Sauna Blood Pressure Cardiovascular

    Nearly 1.3 billion people worldwide have high blood pressure, the primary risk factor for cardiovascular disease-related death. However, findings from a recent study suggest that greater cardiorespiratory fitness offsets some of the risks associated with having high blood pressure.

    The study involved nearly 2,300 middle-aged men enrolled in the Kuopio Ischemic Heart Disease Risk Factor Study, an ongoing study of heart disease risk factors among men and women living in Finland. Researchers measured the participants' blood pressures (classified as normal or high) and cardiorespiratory fitness levels (classified as low, medium, or high).

    They found that high blood pressure increased a person’s risk of cardiovascular disease-related death by 39 percent, and low fitness increased risk by 74 percent. These findings were consistent even after considering other risk factors, including age, body mass index, cholesterol levels, smoking status, type 2 diabetes, coronary heart disease, physical activity, socioeconomic status, and high sensitivity C-reactive protein (a marker of inflammation).

    Men with high blood pressure and low fitness levels were more than twice as likely to die from cardiovascular disease than those with normal blood pressure and high fitness levels. However, men with high blood pressure and high fitness levels were only 55 percent more likely to die from cardiovascular disease.

    These findings suggest that exercise markedly reduces the risk of dying from cardiovascular disease, even among men with high blood pressure. Interestingly, sauna use also reduces blood pressure and the risk of cardiovascular disease-related death. Learn more in this clip featuring Dr. Jari Laukkanen (one of the authors of this study.)

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  • Platelet-derived 'exerkines' produced during exercise promote neurogenesis, boosting brain health and cognition. www.sciencedaily.com
    Exercise Memory Heat Stress Sauna Blood-Brain Barrier

    The benefits of physical activity on the brain’s aging process are widely known. Evidence suggests that exerkines, a class of molecules released into the bloodstream in response to exercise, drive many of these benefits. Findings from a recent study in mice found that PF4, an exerkine derived from platelets, promotes the production of hippocampal precursor cells in the brains of older mice.

    Researchers injected PF4 into mice and assessed its effects on hippocampal neurogenesis (the growth of new brain cells). Then they investigated the effects of exercise on blood platelets.

    They found that systemic elevation of PF4 levels mitigated age-related declines in brain regeneration and cognitive function, an effect that was dependent upon hippocampal neurogenesis. They also found that exercise triggered platelet activation, which in turn increased the production of hippocampal precursor cells in the brains of older mice.

    These findings underscore the crucial role of platelets in mediating the rejuvenating effects of exercise on the aging brain. It also sheds light on the potential mechanisms that link physical activity with improved brain health in aging, with possible implications for people who are unable to exercise due to advanced age, mobility issues, or various health conditions.

    Interestingly, heat stress also promotes PF4. In a study involving endurance cyclists exercising in hot conditions, PF4 increased by as much as 150 percent. Sauna use has similar effects on PF4. Learn about other effects of heat stress from sauna use in our overview article.

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  • Exercise promotes the excretion of heavy metals in sweat. www.ncbi.nlm.nih.gov
    Exercise Sauna

    A 2022 study showed that sweating while exercising promoted the excretion of heavy metals. The sweat produced during exercising contained more heavy metals than that produced during low-temperature sauna use.

    The study involved 12 young, healthy young adults. Researchers collected sweat samples from the participants after 20 minutes of either running on a treadmill or sitting in a sauna cabinet (at ~113°F). Then they measured concentrations of the heavy metals nickel, lead, copper, arsenic, and mercury in their sweat.

    They found that engaging in exercise promoted higher concentrations of nickel, lead, copper, and arsenic in sweat, while sitting in a low temperature sauna did not produce such elevated levels. On the other hand, the sweating method did not affect sweat concentrations of mercury.

    Heavy metals are naturally occurring metallic elements that are toxic or poisonous even at low concentrations. Exposures to heavy metals in everyday products such as arsenic in agricultural products, cadmium in cigarette smoke and automobile exhaust, lead in toys, and mercury in dental amalgam and certain types of fish, are common occurrences.

    These findings suggest that sweating through exercising facilitates heavy metal excretion from the body more effectively than a very low temperature sauna. This was a very small study, however, and larger studies are needed to confirm these findings.

    It’s noteworthy that these findings don’t undermine the utility of sauna use to promote heavy metal excretion in sweat. The average person loses 0.6 to 1.0 kilograms of sweat per hour in a typical traditional sauna session, which is typically considerably hotter (158°F to 212°F) than the experimental conditions used in this study. Consequently, sauna use likely induces considerably greater sweat losses than exercise, depending on the conditions and duration.

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  • Frequent sauna bathing offsets the increased risk of death due to low socioeconomic status
    Mortality Sauna

    Sauna use offsets the increased risk of premature death associated with low socioeconomic status.

    A person’s socioeconomic status – a measure of their income, education, and occupation – is a robust predictor of their overall health and longevity. For example, people of low socioeconomic status typically have less access to financial, educational, social, and health resources than those with a higher socioeconomic status and are at greater risk of developing cardiovascular disease. Findings from a recent study suggest that sauna use negates some of the harmful effects of low socioeconomic status.

    Sauna use induces hyperthermia, an increase in the body’s core temperature that stresses the body and switches on physiological responses involving neuroendocrine, cardiovascular, and cytoprotective mechanisms. These mechanisms work together to restore homeostasis and condition the body for future heat stressors, a phenomenon known as hormesis. Sauna use also mimics many of the cardiovascular effects of exercise, including increased heart rate and blood pressure

    The investigators drew on data from the Kuopio Ischemic Heart Disease Risk Factor Study, an ongoing prospective population-based cohort study of health outcomes in more than 2,500 middle-aged men (42 to 61 years) from eastern Finland, where saunas are readily available. They calculated the men’s socioeconomic status based on information the men provided about their income, education, occupational prestige, standard of living, and housing conditions. They also collected information about the men’s sauna habits and categorized them as infrequent users (two times per week or less) or frequent users (three to seven times per week).

    They found that over a 27-year period, men who were frequent sauna users were 14 percent less likely to die from all causes of premature death than infrequent users. However, men who were infrequent users but had low socioeconomic status were 35 percent more likely to die than men who were infrequent users but had high socioeconomic status. Men who were frequent users but had low socioeconomic status were just 7 percent more likely to die.

    These findings suggest that sauna use offsets some of the increased risk of premature death associated with low socioeconomic status. Although saunas are not as readily available in many locations outside Finland, evidence suggests that very hot baths provide similar health benefits.

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  • Combined exercise and sauna bathing drastically improves cardiovascular fitness. journals.physiology.org
    Exercise Sauna Cardiovascular

    Physical activity is perhaps the most important lifestyle factor in the promotion of heart health because of the beneficial stress it puts on the heart. Sauna bathing puts similar stress on the heart by increasing cardiac output in an effort to cool the body, making it a good choice for people unable to meet exercise guidelines; however, people who combine activities may experience unique benefits. Findings from a report released this month demonstrate the robust beneficial effects of combined physical activity and sauna bathing on cardiovascular fitness and metabolic health.

    Both sauna use and exercise increase pulse and blood pressure, activating a negative feedback loop that lowers blood pressure after the activity is over and for an extended period afterward. Adaptations to the metabolic and mechanical stress of exercise include an increase in heart size and mitochondrial density associated with better cardiovascular output, increased elasticity of blood vessels, and a reduction in white blood cells and inflammation. Previous research shows that sauna bathing provides some of the same benefits; however, because sauna use has just recently moved into the mainstream of clinical research, less is known about its mechanisms of action and effects when combined with exercise.

    The authors recruited 47 participants (average age, 49 years) who did not exercise regularly and were at high risk of cardiovascular disease and randomly assigned them to complete eight weeks of exercise training with or without sauna or no exercise training at all. Participants in the exercise groups completed three days of exercise per week that included a 10-minute warm-up, 20 minutes of weight training, and 30 minutes of aerobic exercise. Participants in the sauna group followed their exercise training with 15 minutes of sauna bathing at 150 degrees Fahrenheit. The temperature of the sauna was increased by 40 degrees Fahrenheit every two weeks as participants acclimated to the heat stress. The participants completed a cardiorespiratory fitness test at the beginning and end of the study during which they peddled an exercise bike at increasing resistance levels to increase heart rate. They also provided blood samples and had their body composition measured.

    Eight weeks of exercise training increased maximal heart rate (measured by VO2max or maximal oxygen intake) and reduced fat mass; however, participants did not experience a significant reduction in blood pressure, arterial stiffness, or total cholesterol compared to the participants who did not exercise. Participants who completed sauna bathing in addition to exercise experienced an even greater increase in maximum heart rate and lower systolic blood pressure (reduction of 8 mmHg in systolic blood pressure and 3 mmHg in diastolic blood pressure) and total cholesterol (12 milligrams per deciliter reduction). Participants in the exercise without sauna group experienced no reduction in systolic blood pressure and only a minor reduction in diastolic blood pressure (0.6 mmHG).

    The findings of this study demonstrate the unique benefits of sauna use in addition to exercise. Future studies with a greater number of participants and more diverse sauna bathing conditions would be valuable additions to this research.

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  • Potential role of passively increased muscle temperature on contractile function link.springer.com
    Heat Stress Muscle Sauna Strength

    Declines in muscle force, power, and contractile function can be observed in older adults, clinical populations, inactive individuals, and injured athletes. Passive heating exposure (e.g., hot baths, sauna, or heated garments) has been used for health purposes, including skeletal muscle treatment. An acute increase in muscle temperature by passive heating can increase the voluntary rate of force development and electrically evoked contraction properties (i.e., time to peak twitch torque, half-relation time, and electromechanical delay). The improvements in the rate of force development and evoked contraction assessments with increased muscle temperature after passive heating reveal peripheral mechanisms’ potential role in enhancing muscle contraction. This review aimed to summarise, discuss, and highlight the potential role of an acute passive heating stimulus on skeletal muscle cells to improve contractile function. These mechanisms include increased calcium kinetics (release/reuptake), calcium sensitivity, and increased intramuscular fluid.

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  • A high-protein diet resulted in 100 percent remission of prediabetes in a small randomized-controlled trial. journals.physiology.org
    Exercise Heart Disease Sauna Blood Pressure Cardiovascular

    Type 2 diabetes is characterized by insulin resistance and chronically elevated blood sugar levels. Weight loss is often part of the primary treatment of type 2 diabetes; however, some weight loss diets may have more insulin-sensitizing effects than others. Findings of one report show that a high protein weight loss diet can reverse prediabetes by increasing insulin-sensitizing hormones.

    Digestion of carbohydrates begins when sweetness receptors in the mouth are activated, leading to the release of insulin and hormones that augment insulin metabolism, such as incretins. In type 2 diabetes, incretins such as glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic peptide (GIP) are reduced, contributing to insulin resistance and increasing abdominal obesity. Pharmaceutical treatments for type 2 diabetes include GLP-1 activators, which can be effective at reducing blood sugar levels and increasing feelings of satiety after eating. High protein diets (30 percent of calories) have also been shown to enhance incretin signaling, making them an important strategy for treating prediabetes.

    The authors recruited 24 participants who had obesity and prediabetes and randomly assigned them to either a high-carb diet (55 percent carbohydrate, 30 percent fat, 15 percent protein) or a high-protein diet (30 percent protein, 30 percent fat, 40 percent carbohydrate) for six months. The diets were designed to produce a 500 calorie per day deficit so that participants would lose weight. Participants completed an oral glucose tolerance test, during which they consumed 75 grams of glucose (equivalent to the amount of sugar in two 12 ounce cans of soda). The researchers measured blood glucose, insulin, GLP-1, and GIP levels during the test.

    After six months, 100 percent of participants consuming the high-protein diet had remission of their prediabetes, while only 30 percent of participants consuming the high-carb diet experienced remission. Participants in both groups experienced weight loss (about 10 percent of their body weight) and improved insulin sensitivity; however, the participants consuming the high-protein diet had higher levels of GLP-1 and GIP and larger reductions in insulin resistance. Importantly, participants consuming the high-protein diet had increased lean muscle mass, while participants in the high-carb protein lost muscle mass.

    These results demonstrate that high protein diets may be an effective strategy for improving insulin sensitivity and reducing type 2 diabetes risk. Learn more about high-protein diets and how to implement them in our new interview with Dr. Stuart Phillips.

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  • Hsp70 shown to preserve locomotor function and reduce cell death through a stable binding to toxic amyloid-beta42, blocking ability to attack neurons www.sciencedaily.com
    Brain Alzheimer's Heat Stress Sauna Neurodegeneration

    Heat shock proteins suppress amyloid-beta toxicity in the brain.

    Amyloid-beta is a toxic peptide that aggregates and forms plaques in the brain with age. These plaques are widely considered a hallmark of Alzheimer’s disease, a progressive neurodegenerative disease that occurs with age and is the most common cause of dementia. Findings from a 2016 study suggest that heat shock proteins suppress amyloid-beta toxicity in the brain.

    Heat-shock proteins comprise a large, highly conserved family of proteins that are present in all cells, across many species. They play prominent roles in many cellular processes and facilitate several aspects of the protein synthesis machinery, including assembly and folding. Increased expression of heat shock proteins prevents protein disorder and aggregation by repairing proteins that have been damaged or misfolded and may offer protection against neurodegenerative diseases and inhibit the aggregation of amyloid-beta, reducing plaque formation.

    The study involved fruit flies, which serve as useful models for studying amyloid-beta anomalies. The investigators engineered a form of heat shock protein 70, called Hsp70, that could pass into the extracellular space and interact with amyloid-beta and studied its effects on the flies' neurological health.

    They found that Hsp70 suppressed the toxicity of amyloid-beta in cells of the flies' eyes, reduced cell death in brain neurons, and helped maintain the neurons' architecture and function. The investigators posited that these neuroprotective effects were directly related to Hsp70’s capacity to bind to amyloid-beta rather than via refolding mechanisms.

    These findings indicate that heat shock protein 70 may suppress amyloid-beta toxicity, thereby reducing amyloid-beta plaque formation in the brain and serving as a potential therapeutic strategy for Alzheimer’s disease. Heat stress, such as that experienced during sauna use, robustly induces expression of heat shock proteins. Learn more about heat shock proteins and sauna use in our overview article.

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  • Whole-body hyperthermia improves aspects of mood. www.tandfonline.com
    Depression Sauna

    A growing body of evidence demonstrates that whole-body hyperthermia improves mood and reduces symptoms of depression. The devices used in many hyperthermia studies have not received FDA approval for investigations conducted in the United States, hindering research progress. Findings from a recent study suggest that a commercially available infrared sauna device induces whole-body hyperthermia and improves aspects of mood.

    Traditional saunas are typically wood-paneled rooms heated by infrared or conventional heaters. However, in recent years, single-person tent-like infrared saunas that spare the head from high temperatures have become popular due to their portability, ease of use, and relatively low cost.

    The study involved 25 physically and mentally healthy males and females (average age, 31 years). Participants completed one whole-body hyperthermia session in a Clearlight Sauna Dome until they achieved a core body temperature of 101.3°F (38.5°C) and maintained that temperature for two consecutive minutes. They remained in the sauna for a 30-minute cool-down period, with the heat turned off. Research staff provided the participants with water and applied cool cloths and ice to their head and neck throughout the sessions. Participants completed questionnaires about their mood and affect before the session and one week later.

    The investigators found that participants reported fewer depression symptoms and less negative affect one week after the sauna session, compared to prior to the session. None of the participants experienced any adverse effects from their session, and most reported only minor complaints related to feeling hot or thirsty.

    These findings indicate that sauna use may reduce symptoms of depression and may be accessible via a widely available commercial sauna device. Learn more about this research in this episode featuring Dr. Ashley Mason.

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  • Winter-swimming alters thermogenesis and resting metabolic rate. www.sciencedaily.com
    Cold Stress Sauna

    Traditional Scandinavian culture promotes sauna bathing, sometimes combined with brief periods of winter-swimming. This exposure to extreme cold promotes the formation of brown adipose tissue, which may enhance metabolic health. Findings of a new report show that winter swimmers have an increased metabolic response to cold temperatures.

    Brown adipose tissue is a type of fat involved in thermogenesis – the production of body heat. Cold-induced thermogenesis involves uncoupling of the mitochondrial electron transport chain, reducing the efficiency of ATP synthesis. This less efficient mode of energy production consumes more calories than normal ATP production and gives off heat as a byproduct. Brown fat activity contributes to overall energy expenditure and the regulation of body fat. Previous research has reported an association between increased brown adipose tissue and better whole-body glucose and insulin sensitivity in adults.

    The authors recruited eight young, healthy males between ages 18 and 35 who participated in winter swimming two to three times per week. Seven participants also used sauna bathing during their winter swimming practice. The authors recruited an additional eight participants who did not participate in winter swimming or sauna bathing and who were matched for age, body mass index, and maximal metabolic rate. The participants provided a blood sample and completed an oral glucose tolerance test to measure glucose sensitivity. The researchers measured body temperature using infrared thermography, body composition using x-ray absorptiometry, and oxygen consumption during a strenuous cycling exercise, a measure of maximal metabolic rate. Finally, the participants completed a sleep study to determine the effects of circadian rhythm on brown adipose tissue metabolism.

    Winter swimmers had a lower core body temperature and reduced uptake of glucose by brown adipose tissue at a comfortable room temperature. They also had lower plasma glucose levels at the end of the glucose tolerance test, suggesting better glucose utilization by skeletal muscle and adipose tissue. When exposed to cold, winter swimmers had a greater increase in thermogenesis compared to participants who did not participate in winter-swimming. Finally, during the sleep study, winter swimmers had increased thermogenesis a few hours prior to waking. Combined with a lower body temperature, these fluctuations in body temperature during the night may improve sleep quality; however, the authors did not measure this variable in the current study.

    The authors conclude that winter-swimming combined with sauna bathing has distinct effects on thermoregulation at room temperature and upon cold exposure. These alterations in metabolism may improve health through increased resting metabolic rate and improved sleep quality. The authors noted that because participants participated in both sauna bathing and winter-swimming, it is not possible to attribute these differences to cold exposure alone.

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  • Whole-body hyperthermia activates muscle hormone irisin and increases neuroprotective factors. www.sciencedirect.com
    Exercise Brain Muscle Sauna BDNF Neurodegeneration

    Exposure to high heat while sauna bathing causes mild hyperthermia – an increase in the body’s core temperature – that induces a thermoregulatory response to restore homeostasis and condition the body for future heat stressors. These adaptations to high temperatures involve increased production of brain derived neurotrophic factor (BDNF), a promoter of neuroplasticity, and irisin, a biomarker of exercise. Findings of a new report demonstrate that whole-body hyperthermia increases BDNF and irisin in healthy young adults.

    Whole-body hyperthermia is a therapeutic strategy used to treat various diseases, including cancer and depression. Previous research has shown that use of a hyperthermia chamber increases BDNF to a greater extent than light intensity exercise. Some research has suggested that BDNF production is stimulated by irisin, a hormone secreted from muscle in response to exercise. Irisin may mediate some of the beneficial effects of exercise and sauna use in humans, but additional research is needed.

    The authors recruited 20 male participants (average age, 22 years) and assessed their baseline heat tolerance using a hyperthermia protocol. Participants reclined in a hyperthermia chamber while the researchers increased the temperature of the chamber by 50 degrees F every ten minutes until the participant reached their personal heat threshold. Next, participants completed ten hyperthermia sessions tailored to their baseline conditioning, during which the hyperthermia chamber was set to a temperature of 150 to 175 degrees F. Following a three-week wash-out period, they completed ten sham treatments over two weeks, during which the hyperthermia chamber was set to a temperature of 75 to 77 degrees F.

    Participants had an average core body temperature of 102 degrees F at the end of each whole-body hyperthermia treatment. Following ten whole-body hyperthermia treatments, participants had a significant increase in circulating irisin levels (6.3 micrograms per milliliter) compared to their baseline levels (5.0 micrograms per milliliter) and compared to their irisin levels following the sham treatment (5.4 micrograms per milliliter). Whole-body hyperthermia treatment also significantly increased BDNF levels (28.3 picograms per liter) compared to baseline (25.9 picograms per liter).

    In healthy young adults, ten whole-body hyperthermia significantly increased irisin and BDNF levels. The authors noted that future studies should explore the effects of whole-body hyperthermia on adipose tissue, which also produces irisin.

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  • Sauna use increases muscle and bone mass. www.mdpi.com
    Sauna

    Aging induces many changes in body composition, even in the absence of changes in body weight. Typically, as a person ages, their fat mass increases, and the muscle mass and bone mineral density decrease. Findings from a recent study suggest that sauna use increases muscle and bone mass.

    Sauna use involves transient exposure to heat, stressing the body and eliciting a wide range of protective responses. Evidence indicates that heat stress may promote muscle growth via activation of pathways involved in protein synthesis and drive osteogenesis via activation of heat shock proteins.

    The intervention study involved 23 healthy young males (average age, 20 years). Participants completed questionnaires regarding their physical activity and nutritional intake. Half of the participants engaged in 12 sauna sessions, performed three times per week for four weeks. Each session consisted of five sets of 10-minute exposures at 100°C (212°F), with five minutes of recovery at 22°C (room temperature, ~72°F) between sets. The other half carried out normal activities for the duration of the study. The participants underwent bioelectrical impedance and dual-energy X-ray absorptiometry (DEXA) to gauge body composition prior to the first sauna session, at the completion of the last sauna session, and two weeks later.

    None of the participants experienced any changes in fat mass during the study. However, the DEXA scans revealed that the men who engaged in the sauna sessions experienced increases in their muscle mass, bone mineral content, and bone mineral density, compared to the men who did not engage in sauna sessions.

    These findings suggest that heat stress encountered during sauna use exerts favorable changes in lean body composition. Learn more about the health benefits of sauna use in this review by Dr. Rhonda Patrick.

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  • Sauna bathing ameliorates the harmful effects of high stress occupations. www.mdpi.com
    Stress Sauna

    Stress is essential to human survival. Long-term exposure to stress, however, increases a person’s risk of developing many chronic diseases. A recent review suggests that sauna bathing protects the body from the harmful effects of high stress occupations and describes the mechanisms that drive the protection.

    People who work in high-stress occupations, such as firefighters, first responders, and military members, are exposed to both physiological and psychological stressors – often referred to as dual stressors. These dual stressors activate physiological responses to stress that ultimately drive inflammation, the underlying cause of many chronic diseases, including atherosclerosis, diabetes, rheumatoid arthritis, and dementia. Many people in high-stress occupations also work long or irregular hours and may have poor or inconsistent dietary patterns.

    Sauna bathing exposes the body to extreme heat. This exposure – a form of stress – increases the body’s core temperature and activates a wide array of protective mechanisms that work together to condition the body for future stressors, a biological phenomenon known as hormesis. Hormesis is a compensatory defense response to a stressor that is disproportionate to the stressor’s magnitude.

    The mechanisms that drive the effects of sauna bathing include activation of heat shock proteins and pro- and anti-inflammatory cytokines; decreased blood pressure and arterial stiffness; and multiple improvements in cardiovascular function. Sauna bathing also improves several aspects of metabolic function, primarily via activation of adenosine monophosphate-activated protein kinase (AMPK), a master regulator of cellular energy homeostasis. AMPK activation influences gene expression and inhibits cellular processes that drive oxidative stress.

    The findings summarized in this review suggest that sauna bathing shows promise as a strategy to ameliorate the harmful effects of the dual stressors experienced by people working in high-stress occupations. Learn more about sauna bathing in our overview article.

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  • Sauna use after endurance exercise improves heat tolerance. link.springer.com
    Sauna

    Exercising in high temperatures stresses the body and reduces performance. Acclimation in a heat chamber improves performance but is costly and time-consuming. A recent study found that supplementing normal endurance training with intermittent post-exercise sauna bathing improves heat tolerance.

    The study involved 20 male and female trained middle-distance runners between the ages of 18 and 22 years. Participants completed 30-minute sauna sessions (101° to 108°C; 214° to 226°F) three times a week for three weeks within roughly five minutes of engaging in low-intensity, continuous outdoor exercise. They underwent heat tolerance tests before and after the intervention.

    The heat tolerance tests revealed that the sauna users' peak rectal temperature decreased 0.2°C (0.36°F); skin temperature decreased 0.8°C (1.4°F); and heart rate decreased 11 beats per minute, compared to those who did not use the sauna. Those who used the sauna also saw improvements in VO2max and speed. The improvements appeared to plateau, however, with four weeks of additional sauna exposure eliciting improvements in rectal temperature only (decrease of 0.1°C, 1.8°F).

    These findings suggest that sauna bathing after engaging in endurance training improves heat tolerance and boosts performance.

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  • Infrared sauna use reduces frailty in older adults. onlinelibrary.wiley.com
    Sauna

    Sauna use is associated with reduced risk for a wide range of age-related conditions, including cardiovascular disease, metabolic dysfunction, and neurodegenerative disease. Evidence from a new study suggests that infrared sauna use reduces frailty in older adults.

    The heat in a sauna is typically provided by conventional electric heaters or infrared heaters. Conventional heaters warm the air to a high temperature, ranging from 70°C to 100°C (158°F to 212°F), and the heat of the warmed air transfers to the body. Infrared heaters emit thermal radiation, which heats the body directly while also warming the surrounding air. They operate at lower temperatures than conventional saunas, typically at 45°C to 60°C (113°F to 140°F).

    Frailty is a progressive biological syndrome defined by the presence of three or more of the following characteristics: unintentional weight loss, fatigue, weakness, slowness, and physical inactivity. Evidence indicates that frailty increases a person’s risk of death.

    The intervention study involved 67 adults between the ages of 66 and 93 years who had been classified as having some degree of frailty. The participants sat in a 60°C infrared sauna for 15 minutes and then rested while lying down and covered with a warm blanket for an additional 30 minutes. The sauna sessions were conducted twice a week for three months.

    The authors of the study assessed the participants' muscle mass, body mass, physical strength, walking speed, cardiorespiratory fitness, cognitive function and mood before and after the intervention. They weighed the participants before and after each sauna session and instructed them to drink sufficient water to compensate for sweat losses.

    They found that 26 percent of the participants showed improvements on measures of frailty. The remainder showed no change (~71 percent) or declined (~2 percent). These findings suggest that infrared sauna use ameliorate measures of frailty in older adults.

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  • Whole-body heat exposure alters skeletal muscle signaling and mitochondrial biogenesis in humans. www.frontiersin.org
    Muscle Sauna

    Muscle loss can occur as part of a disease process, trauma, or aging. Although exercise can prevent muscle loss, some medical conditions or physical limitations can make exercise difficult or even impossible. Findings from a new study indicate that hyperthermia may preserve or increase muscle mass and increase mitochondrial biogenesis.

    Hyperthermia is a state of elevated core body temperature that activates molecular mechanisms that mitigate protein damage and drive the body’s in-house repair systems. Mitochondrial biogenesis is the process by which new mitochondria are made inside cells. Many factors can activate mitochondrial biogenesis including exercise, hyperthermia, and others.

    The study involved nine healthy young men (average age, 35 years) who underwent two 60-minute sessions of passive heat treatment, separated by one week. One session was a whole-body treatment at 44˚C to 50˚C (111˚F to 122˚F) and 50 percent humidity. The other session was a single-leg treatment using a water-perfused suit at approximately 50˚C (122˚F). The authors of the study monitored core, skin and quadriceps muscle temperatures throughout the sessions and took muscle biopsies before, 30 minutes after, and three hours after the heat treatments.

    The whole-body heat treatment switched on the activity of molecules involved in the Akt/mTOR biological pathway, a critical regulator in maintaining skeletal muscle mass. It also increased the expression of heat shock proteins and Nrf2. Nrf2 is a cellular protein that regulates the expression of antioxidant and stress response proteins. Its activity is an indicator of mitochondrial biogenesis. These changes were not evident when the participants received single-leg heat treatment, suggesting that whole-body hyperthermia elicits systemic improvements involved in muscle maintenance and mitochondrial health.

    Interestingly, whole-body heat inhibited the activity of some FOXO proteins and switched on the activity of some genes involved in atrophy. Further study is needed to determine the full effects of whole-body hyperthermia on muscle atrophy.

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  • Sauna use reduces pneumonia risk in healthy, middle-aged men. www.telegraph.co.uk
    Immune System Sauna Protein

    Sauna use promotes mild hyperthermia, which, in turn, induces a wide array of physiological responses. These responses reduce oxidative stress and inflammation and activate cellular defense systems that provide protection against many diseases. Data from a 2017 study suggest that sauna use reduces the risk of developing certain chronic or acute respiratory illnesses, including pneumonia.

    Pneumonia is an acute respiratory illness characterized by cough, fever, chills, and difficulty breathing. It is a common complication of influenza and other viral infections (including the newly emerging coronaviruses) as well as bacterial infections. Pneumonia affects people of all ages, but children, older adults, and people who are immunocompromised are most vulnerable.

    The study, which drew on data from a population-based prospective cohort study of more than 2,000 healthy middle-aged men (42 to 65 years old), was conducted in Finland, where most people have a home sauna. The average sauna exposure reported in the study was approximately 20 minutes per session at 79°C (174°F).

    The data were adjusted for body mass index, smoking status, education level, alcohol consumption, total energy intake, socioeconomic status, physical activity, inflammatory status (measured by C-reactive protein), and history of diabetes, heart disease, asthma, bronchitis or tuberculosis. They revealed that the frequency of sauna use was inversely associated with the incidence of respiratory illness, especially pneumonia. Men who used the sauna two to three times weekly were 27 percent less likely to develop pneumonia than those who used the sauna once weekly or not at all. Men who used the sauna four to seven times weekly were 41 percent less likely to develop pneumonia compared to infrequent or non-users.

    The authors of the study suggested that sauna’s protective effects may be due to reduced oxidative stress associated with hyperthermia or direct beneficial effects on lung tissue.

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  • Aerobic exercise combined with frequent sauna use has a synergistic effect on lowering mortality risks. www.ncbi.nlm.nih.gov
    Heat Stress Sauna Aerobic

    Aerobic exercise improves cardiorespiratory fitness, a measure of the body’s ability to deliver oxygen to skeletal muscles during sustained physical activity. Findings from a study in Finland indicate that good cardiorespiratory fitness combined with frequent sauna use may work in a synergistic fashion to reduce cardiovascular and all-cause mortality.

    Sauna use exposes the body to extreme temperatures that stress the body, eliciting physiological responses that are remarkably similar to those experienced during moderate- to vigorous-intensity exercise. Prospective studies conducted in Finland revealed that men who used the sauna four to seven times per week were 50 percent less likely to die from cardiovascular-related causes and 40 percent less likely to die from all causes of premature death.

    In a separate analysis, data from the Finish cohort also demonstrated that a high level of cardiorespiratory fitness or frequent sauna use were both independently associated with reduced cardiovascular-related mortality and all-cause mortality. In addition, cardiorespiratory fitness in combination with frequent sauna bathing (three to seven sessions per week) had a synergistic effect on lowering cardiovascular and all-cause mortality. The strongest reductions in mortality were found in people with high cardiorespiratory fitness and high frequent sauna bathing, followed by high cardiorespiratory fitness and low frequent sauna bathing, and then low cardiorespiratory fitness and high frequent sauna bathing.

    Sauna bathing is safe for most adults and can be practiced before or after aerobic exercise to augment the beneficial effects of exercise.

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  • US Saunas Incapable of Reaching Temps Necessary for Theraputic Effects?
    Sauna

    I have recently been made aware that in the USA, at least to obtain UL (Underwriters Laboratory) certification, a sauna heater must not heat above 194 °F. Further that the sauna temperature sensor controlling the heater much be located above the heater – not, for example, on the opposite side of the sauna enclosure.

    The studies that validated the use of traditional saunas for health benefits would all have been done at “temperatures typically between 70 and 100 °C (158 and 212 °F)” – which is the normal air temperature of a sauna in Finland, right? The quoted text is from Wikipedia.

    If so we may be fooling ourselves into thinking we can get those benefits via a sauna we might frequent in the USA.

    The sauna I use reaches 140-150 °F across the main sauna bench when it is cranked up to its maximum 194 °F. It could be that the higher European temperatures are unnecessary, but given that those are the temps at which the validation studies were conducted, I have no basis for thinking lower temps would be effective.

    BTW, it looks like that even obtaining the actual UL code book for this would run > $700, so I can’t say for sure whether UL even requires this of sauna heaters. If you would like to purchase a copy and let us know, please visit this URL: https://www.shopulstandards.com/ProductDetail.aspx?productId=UL875_9_B_20090521(ULStandards2)

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  • Daily heat treatments, applied during 10 days of immobilization, prevented the loss of mitochondrial function and prevented muscle atrophy. www.physiology.org
    Heat Stress Muscle Sauna Protein Dairy

    A new study found that daily heat treatments applied locally to muscle during 10 days of immobilization prevented the loss of mitochondrial function, increased heat shock protein levels, and attenuated skeletal muscle atrophy by 37% compared to sham control in a small trial in humans.

    I am really glad to see this replicated now in humans. There’s were two similar studies that I covered in past videos, which showed that whole body heat treatment (similar to a sauna) prevented muscle atrophy and increased muscle regrowth after immobilization, however, these were done in mice. The difference is that this shows a pretty similar phenomenon in humans! This isn’t too surprising. The main reason for that is because the mechanism in animal research was already all worked out. The prevention of muscle atrophy and muscle regrowth in mice was shown to be dependent on the robust activation of heat shock proteins. These proteins are highly conserved in humans in function, playing an extremely apparent similar molecular role. More importantly, we already knew from prior research that heat shock proteins increase by ~50% after 30 minutes in a 163 ºF (73 ºC).

    The results of this new study have important implications. While exercise interventions remain the most effective strategy to maintain or increase muscle mass and respiratory capacity, during periods of immobilization due to injury or for other reasons exercise can become more challenging. Heat therapy through modalities such as a sauna or even local heating (as is the case in this study) may ultimately serve as a very useful alternative or adjunct therapy to maintain skeletal muscle metabolic function and preserve muscle mass!

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  • New comprehensive analysis of the literature by @LaukkanenJari shows frequent sauna use may reduce the risk of heart disease, neurocognitive diseases. www.mayoclinicproceedings.org
    Heat Stress Sauna Blood Pressure

    New comprehensive analysis of both prospective studies and clinical trials shows frequent sauna use may reduce the risk of heart disease, neurocognitive diseases, mental health disorders, pulmonary diseases, and mortality.

    Temperature, duration, and frequency are in the review. Most of the studies show benefits with a sauna temperature of around 174F for 20 minutes at least 2-3 times per week. Sauna use 4-7 times per week had the most robust effects.

    This review is authored by Dr. Jari Laukkanen. His research has shown that frequent sauna bathing reduces blood pressure, inflammation, oxidative stress, cholesterol, arterial stiffness, and vascular resistance. He has also shown that sauna use contributes to beneficial levels of circulating hormones and other cardiovascular markers.

    You can learn more about the beneficial effects of sauna use on the heart and brain by checking out my podcast with the author of this study, Dr. Jari Laukkanen.

    Sauna episode: https://www.foundmyfitness.com/episodes/jari-laukkanen

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  • Using the sauna was associated with a decrease in a biomarker of inflammation (CRP) in a dose-dependent manner. www.ncbi.nlm.nih.gov
    Inflammation Heat Stress Sauna

    A new study found that using the sauna was associated with a decrease in a biomarker of inflammation (CRP) in a dose-dependent manner. The more frequent the sauna use…the more robust the effect of lowering inflammation. This study was published early this year from with one of the world’s leading sauna researchers, Dr. Jari Laukkanen.

    He has also shown dose-dependent effects with sauna use on cardiovascular disease, all-cause mortality, and Alzheimer’s disease. Using the sauna 2-3 times per week (20 minutes at 174º F) was associated with: 27% lower cardiovascular disease risk, 24% lower all-cause mortality, and a 20% lower risk of Alzheimer’s disease compared to men that only used the sauna one time per week. Using the sauna 4-7 times per week (20 minutes at 174º F) was associated with: 50% lower cardiovascular disease risk, 40% lower all-cause mortality, and a 66% lower risk of dementia and a 65% lower risk of Alzheimer’s disease compared to men that used the sauna once a week.

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