Episode 69: The Science & Health Benefits Of Deliberate Heat Exposure | Huberman Lab

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Key Takeaways

  • Regular use of sauna and other heat exposure can reduce mortality by cardiovascular events, stroke, and all-cause mortality
  • Effects of deliberate heat mimic cardiovascular exercise
  • General guideline to start heat stimulus: temperature must be between 176F-212F for 5-20 minutes, 2-7 times per week – later in the day is better to activate cooling mechanisms and assist with sleep
  • Find what works for you: choose either higher heat intensity and shorter bouts, or lower heat intensity and longer bouts – but always between 176F-212F
  • Make sure you’re replacing the water you lose in the sauna – drink at least 16 ounces of water for every 10 minutes of sauna use
  • If growth hormone increase is your main goal for sauna use, limit to 1x/week or 1x/10 days – and enter fasted or without food in the 2-3 hours prior for maximum benefits
  • Proper application of local heat may actually change the identity of fat cells at that location and encourage the conversion of white fat to beige fat

Introduction

Dr. Andrew Huberman, Ph.D. is a Professor of Neurobiology and Ophthalmology at Stanford University School of Medicine. His lab focuses on neural regeneration, neuroplasticity, and brain states such as stress, focus, fear, and optimal performance.

In this episode, Andrew Huberman describes the mechanisms by which deliberate heat exposure impacts body temperature, metabolism, heart health, hormone production, exercise recovery, cognition, mood, and longevity.

Host: Andrew Huberman (@hubermanlab)

How Do Our Bodies Heat Up?

  • Our body can heat up from outside in or inside out
  • We have two body temperatures: (1) skin/shell; (2) core (organs, viscera, spinal cord)
  • The brain is constantly sending signals to the body’s heating and cooling system based on the environment
  • If you throw a cold towel on your body, your brain will actually think you need to heat up your core
  • In a hot environment, the brain tries to cool down your core
  • The transition between hot and cold temperatures engages the process of heating and reheating
  • Heating up mechanism: (1) skin has neurons that sense changes in heat; (2) electrical signals are sent to the spinal cord; (3) signals are sent to the brain – specifically the preoptic area (POA) which send signals to the brain & body and trigger behavioral responses
  • The impulse to get yourself out of a hot environment is the consequence of the POA communicating with the amygdala and in turn activating adrenal glands
  • A word of caution: there’s a lot more wiggle room when it comes to cold and cooling the body than there is to heat – the neurons are quite sensitive to heat and once they’re damaged, they’re gone
  • Humans unload heat by sweating

Deliberate Heat Exposure Changes Biology

  • “Deliberate heat exposure can be a powerful tool to improve health and longevity.” – Dr. Andrew Huberman
  • Regular use of sauna and other heat exposure can reduce mortality by cardiovascular events, stroke, and all-cause mortality
  • Defining sauna use: temperature between 80C-100C or 176F-212F (depending on how hot it feels to you), 5-20 minutes per session, 2-7 times per week
  • You will become better adapted and better at sweating excess heat with frequent exposure
  • Options if you don’t have access to a sauna: try hot water bath up to the neck; wear a plastic suit (like fighters trying to drop weight)
  • Wet sauna and dry sauna are both acceptable; most infrared saunas don’t get hot enough
  • Biological changes to heat: blood flow, plasma, stroke volume, and heart rate all increase – which the body perceives as similar to cardiovascular exercise
  • Hormone effects of heat: decrease in cortisol output
  • Activation of heat shock proteins (HSP): heat changes the way in which proteins are configured at a molecular level – HSP makes sure cells of the brain and body don’t misfold
  • Heat for lifespan: heat upregulates pathways (FOXO3) related to DNA repair and clearing out of senescent cells
  • Heat for metabolic enhancement: recipe seems to be 57 minutes per week (total, spread out across sessions) of heat exposure – cold exposure recipe is 11 minutes per spread out of the uncomfortable but safe cold
  • Hormesis: subjecting yourself to enough stress to induce adaptation of some kind

Use Of Sauna To Increase Growth Hormone

  • Growth hormone: impacts metabolism and growth of cells and tissues of the body, responsible for tissue repair and growth spurt during puberty
  • Starting in the early 30s, growth hormone release is greatly diminished
  • Sauna exposure increased growth hormone 16 fold – important caveat, effect on growth hormone went down with increased sauna use because body becomes heat adapted
  • If growth hormone increase is your main goal for sauna use, limit to 1x/week or 1x/10 days – and enter fasted or without food in the 2-3 hours prior for maximum benefits

Deliberate Heat Exposure For Improved Mood & Wellbeing

  • The endorphin system is activated when we experience short stress
  • Dynorphin system: the struggle of heat exposure ultimately activates pathways that lead to an increase in the baseline level of mood and heightened level of happiness and improved mood

Adjusting Body Heat With Glabrous Skin Surfaces

  • Glabrous skin: hair-free skin found in palms of hands, soles of feet, the upper half of the face
  • Glabrous skin surfaces can be leveraged to cool the blood and core of the body
  • To warm a cold body: use a warm blanket or warmer on glabrous surfaces
  • To cool a hot body: use a cool compress, frozen or cold materials on glabrous surfaces
  • Fever is natural heat inoculation designed to kill pathogens in the body

Types Of Fat & Responses To Temperature

  • Cold exposure (11 minutes per week, up to the neck) has been shown to increase brown fat which increases metabolism and the ability to feel comfortable in cold temperatures
  • Local heat exposure (not to the point of burning) converts white fat to beige fat which leads to systemic increases in thermogenesis, metabolism, and fat loss – children have a lot of brown and beige fat
  • Beige fat is a more metabolically active version of white fat

Sources

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Notes By Maryann

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