The Science & Health Benefits of Deliberate Heat Exposure

The Science of Heat and Heating

• Heat has a profound effect on our biology
• Can impact metabolism, cognition, and overall health
• Proper application of heat can improve brain function

Sauna and Local Heating

• Sauna: how often, how long, and how hot for specific goals and outcomes
• Local heating: applying heat to specific areas of the body to heal or improve tissues
• Recent study: local heating can change the identity of fat cells, converting white fat to beige fat

Biology of Heat and Heating

• We heat up from the outside (environment, clothing) and the inside (body’s ability to generate heat)
• Two body temperatures: skin (shell) and core (viscera, organs, nervous system)
  Understanding Body Temperature Regulation
• Two body temperatures: shell (surface) and core (inside)
• Brain constantly sends signals to regulate these temperatures
• Similar to a thermostat in a room

Heating and Cooling Mechanisms

• Brain has neurons that send signals to cells in the body
• Releases chemicals to heat up when cold and cool down when hot
• Understanding the balance between shell and core temperatures is crucial for designing effective protocols

Using Heat for Health and Performance

• Sauna, hot tub, and hot shower can be powerful tools for optimizing biology
• Important to understand heat as a process, not just a static temperature
• Transitioning between hot and cool environments can increase growth hormone release

Caution with Heating

• Be cautious when heating up the body, as it can lead to neuron damage
• Pregnant, nursing, or heat-​​sensitive individuals should avoid saunas and other heat-​​related tools
• Always consult a doctor before trying any heat-​​related protocols

Circuit for Heating Up and Cooling Down

• Neurons in the skin sense changes in heat and send signals to the spinal cord
• Signals travel from the spinal cord to the lateral parabrachial area, then to the preoptic area (POA) in the hypothalamus
• POA sends signals to the rest of the brain and body to regulate temperature and change behavior accordingly
  Heat Exposure and Health Benefits
• Deliberate heat exposure can improve health and longevity 
  • Study: Sauna Bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women
  • Regular use of sauna or other forms of deliberate heat exposure can reduce mortality from cardiovascular events and other health issues
• Temperature ranges for sauna: 80°C (176°F) to 100°C (212°F)
  • Duration: 5 to 20 minutes per session
  • Frequency: 1 to 7 times per week
• Benefits of sauna use: 
  • 2–3 times per week: 27% less likely to die of a cardiovascular event compared to once a week
  • 4–7 times per week: 50% less likely to die of a cardiovascular event compared to once a week
• Study controlled for confounding variables such as smoking, weight, and exercise habits

Heat Exposure Circuit

• Skin to spinal cord to preoptic area (POA) in the brain 
  • POA can trigger autonomic subconscious responses to heat (e.g., sweating, vasodilation)
  • POA can trigger behavioral responses (e.g., spreading out limbs, feeling lethargic)
  • POA can trigger a panic response to get out of a hot environment by communicating with the amygdala

Heat Dumping Mechanisms

• Physiological (below conscious control): sweating, vasodilation
• Behavioral (somewhat voluntary): lethargy, spreading out limbs
• Other animals: dogs pant, rodents spit on their paws and rub it on their body

Heat and Lethargy

• Relationship between temperature and lethargy is intimate 
  • Warm enough: active and want to move around
  • Too warm: need to stay put, spread out limbs, and dump heat
    Sauna and Health Benefits
• 27% less likely to die of a cardiovascular event for those using sauna 2–3 times a week
• 50% less likely to die of a cardiovascular event for those using sauna 4 times a week
• Regular sauna exposure reduces all-​​cause mortality

Sauna Alternatives

• Hot tub or hot water bath up to the neck
• Wearing heavy clothing and exercising in a hot environment
• Dry sauna, steam sauna, or infrared sauna

Sauna Temperature and Duration

• Aim for 80–100 degrees Celsius (176–212 degrees Fahrenheit)
• 5–20 minutes per session
• Wet or dry sauna, personal preference
• Infrared sauna: ensure it reaches the desired temperature range

Biological Mechanisms of Sauna

• Activates neurons in the preoptic area (POA) of the brain
• Increases blood flow, plasma volume, stroke volume, and heart rate
• Mimics cardiovascular exercise without joint and limb stress

Hormone Effects of Sauna

• Study: Endocrine Effects of Repeated Hot Thermal Stress and Cold Water Immersion in Young Adult Men 
  • 4 sauna sessions of 12 minutes each at 90–91 degrees Celsius (194 degrees Fahrenheit)
  • 6‑minute cooldown break in cold water (10 degrees Celsius, 50 degrees Fahrenheit)
• Results: significant decrease in cortisol (stress hormone) output
• Sauna can help control stress and cortisol levels
  Ashwagandha and Stress Management
• Ashwagandha should not be used for extended periods (longer than two weeks)
• Breath work protocols can help reduce stress response in real time

Sauna Protocols for Stress Reduction

• 12-​​minute exposure to 90-​​degree Celsius environment
• 6‑minute cooldown break in cool water (50 degrees Celsius)
• No significant shifts in testosterone, prolactin, or DHEA with this protocol

Heat Shock Proteins (HSPs)

• Activated in response to hot environments
• Rescue proteins that would otherwise misfold due to heat
• Short-​​term activation is beneficial, long-​​term activation can be problematic

Sauna Exposure and Longevity

• Fruit fly study: 70-​​minute heat stimulus extended life by 15% in a heat shock-​​dependent way
• Human studies: Sauna exposure 2–3 times per week (80–100 degrees Celsius) upregulates FOXO3, involved in DNA repair pathways and clearing senescent cells
• Individuals with additional or hyperactive FOXO3 are 2.7 times more likely to live to 100 years or longer

Sauna and Cold Exposure for Metabolism

• Study by Susannah Soberg: 57 minutes per week of sauna exposure and 11 minutes per week of cold exposure improved metabolism and increased brown fat
• Sauna sessions can be divided into shorter sessions throughout the week
  Sauna and Growth Hormone
• Sauna can increase growth hormone levels 
  • Growth hormone is responsible for tissue repair and growth spurt during puberty
  • Secretion of growth hormone decreases with age
• Study on sauna and growth hormone 
  • 80°C (176°F) environment for 30 minutes, four times per day
  • Conducted on day 1, day 3, and day 7 of a week
  • Results:
    • Day 1: 16-​​fold increase in growth hormone
    • Day 3: 3–4 fold increase in growth hormone
    • Day 7: 2–3 fold increase in growth hormone
• Growth hormone response diminishes with frequent sauna use 
  • Body adapts to the heat exposure, reducing the shock to the system
  • To maximize growth hormone increase, limit sauna use to once a week or once every ten days

Cold Exposure and Growth Hormone

• Cold exposure can also impact growth hormone levels 
  • Cooling the body’s shell heats up the core
  • Preoptic area of the hypothalamus controls both heating and cooling of the body
• Understanding the relationship between heat and cold exposure can help design optimal protocols for deliberate heat exposure
  Cold and Heat Exposure Effects on Norepinephrine and Dopamine
• Cold water exposure (4°C for 20 seconds) can cause a 200–300% increase in norepinephrine (noradrenaline)
  • Norepinephrine and dopamine increase mood, focus, and alertness
• Longer exposure to less intense cold (6 hours at 16°C) can lead to even greater increases in norepinephrine
• Heat exposure can stimulate heat shock proteins, growth hormone, etc.

Optimal Timing for Cold and Heat Exposure

• Cold exposure is best done early in the day to match the natural increase in body temperature across the 24-​​hour circadian rhythm
• Heat exposure is best done later in the day, as it activates cooling mechanisms and helps the body cool down, making it easier to fall asleep

Maximizing Growth Hormone Release with Sauna

• To optimize growth hormone release and sleep, do sauna in the evening or at nighttime
• Take a warm or cool shower afterwards to rinse off sweat and prepare for sleep
• Keep glucose and insulin levels low in the bloodstream, as elevated levels can blunt growth hormone release
• Sauna once or twice a week, ideally fasted or without ingesting food 2–3 hours before

Study on Growth Hormone Response to Stress Stimuli

• Study: “Growth Hormone Response to Different Consecutive Stress Stimuli in Healthy Men: Is there any difference?” published in the journal Stress
• Findings:
  • Doing sauna once and then again later that day led to a big increase in growth hormone the first time, but less the second time
  • Exercise followed by sauna did not result in twice as much growth hormone release
  • Releasing growth hormone reduces the likelihood of releasing it again later that day
    Effects of Sauna on Fasting, Growth Hormone, and Mood
• Sauna use can increase growth hormone levels 
  • Wait a couple of hours after eating before using a sauna for maximum growth hormone release
• Sauna use can aid in sleep 
  • Decreases in body temperature after sauna use can help with the transition to sleep
• Hydration is important after sauna use 
  • Drink at least 16oz of water for every 10 minutes spent in the sauna
• Sauna use can improve mood and mental health 
  • Deliberate heat exposure can upregulate pathways that allow for experiencing pleasure
  • Endorphins are released in response to stressors, such as heat exposure 
    • Dynorphin is an endorphin that causes discomfort and stress in response to heat exposure
    • Over time, the binding of dynorphin to the kappa receptor leads to increased efficiency in the “feel good” endorphin system
  • Sauna use can improve baseline mood and heighten positive emotions in response to positive events

Dinorphin and Stress

• Dinorphin is involved in stress and depression, as well as alcoholism 
  • Chronic alcohol use can cause changes in dopamine receptors, making it difficult to achieve pleasure through other means
  • Dinorphin appears to be the “pain molecule” in the context of pleasure and pain balance
• Deliberate heat exposure can leverage the dinorphin system to improve mood after sauna use

Sauna Bathing and Risk of Psychotic Disorders

• A 2018 study found a relationship between sauna bathing and a reduced risk of psychotic disorders 
  • Further research is needed to understand the mechanisms behind this relationship
    Sauna Use and Mental Health
• Study explored the relationship between mental health and sauna use 
  • Over 2000 subjects with no history of psychotic disorders
  • Classified into three groups based on sauna frequency (1x, 2–3x, or 4–7x per week)
• Results showed a strong inverse association between frequent sauna use and future risk of psychotic disorders 
  • Not causal, but correlative
  • Frequent sauna use may be related to other health-​​promoting activities

General Benefits of Sauna Use

• Sauna use (5–20 minutes, 1–7 times per week) is associated with: 
  • Improved cardiovascular health
  • Improved mental health
• Can be done with minimal cost (hot bath, bundling up and jogging, or using a sauna)

Heating and Cooling Specific Body Parts

• Glabrous skin surfaces (upper half of the face, palms of hands, bottoms of feet) can be used to heat or cool the body quickly 
  • These areas have arteriovenous anastomoses (AVAs) which allow for faster heat exchange
• Cooling the body: 
  • Use cool towels or objects on the palms, bottoms of feet, and upper half of the face
  • Avoid using ice packs as they may constrict veins
• Heating the body: 
  • Use warm objects or fluids on the palms, bottoms of feet, and upper half of the face
  • Be cautious not to burn the skin

Fever as a Protective Mechanism

• Fever is an adaptive response to kill pathogens 
  • Most pathogens don’t survive well at high temperatures
• Taking medications to reduce fever may short-​​circuit this protective mechanism
• Safe ranges for body temperature vary between infants and adults

Local Hyperthermia and Fat Conversion

• Deliberate cold exposure can increase brown fat stores 
  • Brown fat is metabolically active and helps with cold tolerance
  • General protocol: 11 minutes total per week of uncomfortable yet safe deliberate cold exposure (ice bath, cold shower, etc.)
    Local Hyperthermia Therapy and Fat Conversion
• Local hyperthermia therapy involves heating a specific body surface
• Converts white fat to beige fat, leading to increased metabolism and fat loss
• Study published in Cell Press Journal, performed on mice and humans
• Heated skin to 41°C (105.8°F) without damaging it
• Local heating of skin increased UCP One, which increases mitochondrial function
• Also increased heat shock factor one (HSF One) and A2B1, involved in glucose and lipid metabolism
• Increases in beige fat occurred in typical locations (around the spine, upper neck, clavicles)
• Provides another potential mechanism to increase beige fat, in addition to deliberate cold exposure
• Local skin heating should be done cautiously to avoid skin damage

Hormesis

• The concept of subjecting oneself to enough stress to induce adaptation
• Examples include adapting to cold water exposure, cardiovascular exercise, and resistance training
• Leads to growth or strengthening of muscles, improvement in cardiovascular function, and other adaptations
  Mitohormesis and Stressful Stimuli
• Mitohormesis: stressful stimuli activating pathways like UCP One and HSF One can induce changes in mitochondria, leading to increased metabolism
• Cold, heat, exercise, and other forms of stress can lead to increased metabolism and conversion of white fat to beige fat
• Different protocols activate these pathways to varying degrees

Sauna and Heat Exposure Benefits

• Growth hormone increases: infrequent sauna or heat exposure (once per week or less) with multiple sessions on that day
• Cardiovascular and longevity benefits: frequent sauna or heat exposure (3–4 or even 7 times per week)
• Mental health benefits: getting uncomfortable in a safe heat environment to increase dynorphin and endorphin effects on mood
• Timing: after a workout or later in the day for sleep benefits (due to post-​​sauna cooling effect)