Key Moments
AMA #7: Cold Exposure, Maximizing REM Sleep & My Next Scientific Studies
Andrew HubermanKey Moments
Cold exposure can boost immunity but avoid it when sick. Nasal breathing is key.
Key Insights
Deliberate cold exposure generally does not directly cause illness, but environmental factors like cold, dry air can increase susceptibility.
If you are feeling sick (malaise, cold, flu), avoid deliberate cold exposure and opt for rest, warm baths, or saunas.
Regular, deliberate cold exposure can increase immune markers over time, likely due to the release of epinephrine and norepinephrine.
While cold exposure can enhance immune function, excessive or chronic elevation of stress hormones like epinephrine can suppress immunity.
Practicing nasal breathing is generally beneficial for respiratory health and defense against infections compared to mouth breathing.
The Huberman Lab Premium channel supports the free podcast and funds scientific research, with a dollar-for-dollar match from the Tiny Foundation.
COLD EXPOSURE AND ILLNESS RISK
Directly getting sick from deliberate cold exposure, such as brief plunges into cold water, is unlikely, provided the water is clean. The primary risk of infection from cold environments stems more from the ambient conditions, like cold, dry air, which can compromise the protective mucous linings in the nose and mouth. Therefore, while the cold water itself isn't typically the culprit, the environment surrounding the exposure, particularly if it leads to prolonged shivering or mouth breathing in dry air, could increase vulnerability to viruses and bacteria.
ADVISING AGAINST COLD EXPOSURE WHEN UNWELL
It is strongly advised to avoid deliberate cold exposure if you are experiencing symptoms of illness, such as malaise, a cold, or the flu. During sickness, the body's resources are best directed towards recovery. Engaging in stressful activities like cold plunges or intense heat exposure diverts energy that should be focused on fighting infection. Instead, when feeling unwell, prioritizing rest, warm baths, or gentle saunas is recommended to support the natural healing processes.
IMMUNE SYSTEM ENHANCEMENT THROUGH COLD EXPOSURE
Consistent, deliberate cold exposure can lead to measurable increases in immune system markers over time. Studies suggest that regular practice, such as three times a week for several weeks, can lead to trends of increased immune cells like T lymphocytes and immune molecules such as IL-6. This effect is largely attributed to the acute release of stress hormones like epinephrine and norepinephrine, which can temporarily bolster immune responses and prepare the body to combat potential infections.
THE DUAL ROLE OF ADRENALINE AND NORADRENALINE
The hormones epinephrine and norepinephrine, released during cold exposure and other stress responses, play a complex role in immunity. While their release can be 'pro-immune' in the short term, helping to activate immune cells, chronic or excessive elevation of these hormones, especially late in the day, can actually have a suppressive effect on the immune system. This highlights the importance of balancing cold exposure with adequate recovery and avoiding overstimulation.
BENEFITS OF NASAL BREATHING
Maintaining nasal breathing whenever possible, except during strenuous exercise or specific activities, offers significant health advantages. The nasal passages act as a crucial first line of defense against airborne pathogens by trapping viruses and bacteria in mucus. Contrasted with mouth breathing, nasal breathing helps keep the respiratory tract moist and better protected. This practice can reduce the likelihood of infections and improve overall respiratory resilience.
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UNDERSTANDING SICKNESS BEHAVIOR
When the body detects a viral or bacterial infection, specific brain circuits are activated that promote 'sickness behavior.' This includes a natural inclination to reduce movement, adopt a more withdrawn posture (like the fetal position), and generally conserve energy. This response is not accidental but a biological mechanism designed to optimize recovery by dedicating all available resources to fighting the infection and facilitating healing.
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Common Questions
Directly from the cold exposure itself, it's unlikely to make you sick, especially if exposures are brief (1-10 minutes) and you warm up afterward. However, prolonged exposure to cold, dry air, particularly with mouth breathing, can increase susceptibility to infections by drying out mucosal linings.
Topics
Mentioned in this video
Institution where Andrew Huberman is a professor, supporting research on human beings.
A bacterium used in a study involving endotoxin injections to induce sickness symptoms, which participants could ward off with specific breathing techniques.
Organization that matches funding for research studies generated through the Huberman Lab Premium channel.
A podcast that discusses science and science-based tools for everyday life, with a standard free version and a premium subscriber channel.
A study that investigated the effects of cold exposure on the immune system, finding trends towards increased immune markers with repeated exposure over six weeks.
A study published in PNAS that examined how voluntary control of the sympathetic nervous system, through methods like cyclic hyperventilation, can attenuate the innate immune response.
Immune cells that showed a trend towards increased numbers with repeated cold exposure.
A type of immune cell showing a trend towards increased numbers with repeated cold exposure.
A type of immune cell showing a trend towards increased numbers with repeated cold exposure.
A component of E. coli used in a study to induce sickness symptoms like fever, vomiting, and diarrhea in participants.
A breathing technique involving cyclic hyperventilation, which can deploy epinephrine and norepinephrine and has been shown to attenuate certain immune responses.
A molecule released in response to cold water exposure and deliberate hyperventilation, which can be pro-immune in the short term.
Immune cells that showed a trend towards increased numbers in a study of repeated cold exposure.
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