Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health

Cold Exposure and the Nervous System

• Sympathetic nervous system responsible for accelerations in heart rate, feelings of alertness, and stress response
• Catecholamines: dopamine, epinephrine, and norepinephrine
• Cold exposure activates sympathetic nervous system and catecholamines
• Cold shock: activation of sympathetic nervous system and catecholamines, causing hyperventilation and gasping reflex
• Adaptation to cold exposure can reduce the shock response

Cold Exposure Protocols

• Uncomfortably cold temperatures are ideal for cold exposure
• Cold shock response can be used as a gauge for cold exposure
• People vary in their ability to embrace the discomfort of cold exposure
• More sensitive nervous systems may feel more pain from cold exposure

Types of Cold Exposure

• Cold water immersion: more potent activation of cold receptors in the skin, rapid activation of autonomic nervous system
• Cold air exposure: activates sympathetic nervous system, increases norepinephrine, and activates brown fat
• Cold showers: activates brown fat immediately, potentially increases metabolism

Brown Fat Activation

• Brown fat: healthy fat tissue that increases metabolism when activated
• Activated by cold exposure on the skin
• First responder in the body to maintain temperature
• Muscles are the secondary tissue to increase thermogenesis through shivering

Cold Shower Studies

• Fewer studies on cold showers due to methodological challenges
• Difficult to control variables such as water direction, body size, and clothing

• Cultural and logistical barriers to conducting cold shower research in laboratories
  Cold Exposure and Brown Fat Activation

• Cold exposure activates brown fat 
  • Cold receptors in the skin send signals to the hypothalamus
  • Hypothalamus activates brown fat
  • Direct pathway from cold receptors in the skin to brown fat
  • Shivering in muscles also activates brown fat
• Shivering is a natural response to cold and can be beneficial 
  • Increases metabolism and burns calories
  • Trains cells and muscles, increasing insulin sensitivity
  • Creates healthy stress (hormesis) in cells, making them more robust
• Long-​​term benefits of cold exposure 
  • Increases catecholamines (dopamine, norepinephrine, epinephrine) for hours after exposure
  • Improves blood pressure
  • Enhances metabolism and brown fat function
  • Increases cold tolerance and overall “fitness” for cold environments

The Importance of Shivering

• Shivering should not be avoided, as it is a natural response to cold 
  • Trains cells and muscles, increasing insulin sensitivity
  • Creates healthy stress (hormesis) in cells, making them more robust
• Shivering can be compared to exercise 
  • Both create healthy stress in cells and improve overall health
  • Both increase metabolism and burn calories
  • Both train the body to be more resilient and adaptable

Adaptations from Cold Exposure

• Regular cold exposure leads to adaptations in the body 
  • Improved cold tolerance
  • Enhanced metabolism and brown fat function
  • Increased insulin sensitivity
  • Lower blood pressure and inflammation at rest
    Cold Exposure and Adaptation
• Cold exposure leads to increased comfort and adaptation 
  • Metabolic changes, such as increased brown fat activation
  • Improved capillary constriction in the skin
  • Reduced stress response and catecholamine release over time
• Increased metabolism and insulin sensitivity 
  • Study by GIBR Stormer et al. (2016) showed improved insulin sensitivity in middle-​​aged men and women after a winter swimming season
  • Lower blood pressure and heart rate observed after the season

Blood Pressure and Cold Exposure

• Blood pressure is a crucial factor in overall health 
  • Cerebrovascular and cardiovascular diseases are leading causes of death worldwide
  • Controlling blood pressure is essential for preventing these diseases
• Deliberate cold exposure can help control blood pressure, especially when combined with other forms of exercise

Brown Fat

• Brown fat is plastic, meaning it can grow and decrease 
  • Can be activated by increased norepinephrine in the body
  • Studies show that brown fat can grow in response to certain conditions, such as pheochromocytoma (a tumor on the adrenal gland)
• Brown fat decreases with age, potentially leading to obesity 
  • Insulin sensitivity decreases as brown fat decreases
• People who work outside and engage in physical labor tend to have more brown fat and better overall health 
  • Improved insulin sensitivity and glucose balance
  • Lower blood pressure and heart rate

Insulin Sensitivity

• Insulin sensitivity is a desirable trait for overall health 
  • Insulin insensitivity is associated with type 2 diabetes and obesity

• Regular physical activity and cold exposure can help maintain insulin sensitivity and overall health
  Brown Fat Activation and Cold Exposure

• Brown fat can be activated with just a little bit of exposure to cold 
  • Cold is the most potent stressor activator of brown fat
  • Studies have shown that just putting a hand in cold water can activate brown fat
  • Going outside in a T‑shirt, wearing cooling vests, or exposing oneself to cold wind can activate brown fat
• Sleeping in a cold room can also activate and grow brown fat 
  • Studies have shown that sleeping in 19 degrees Celsius can activate and grow brown fat
  • Increased insulin sensitivity observed in subjects who slept in 19 degrees Celsius for a month
• Brown fat activation can help decrease unhealthy white fat and improve insulin sensitivity
• Cold adaptation can occur rapidly due to the growth of more mitochondria in brown fat cells

Scandinavian Saying about Cold Exposure

• In the fall, wear fewer layers to prepare for the cold of winter and activate brown fat

• In the spring, wear more layers to be a little uncomfortably warm, so that in the heat of the summer, the body is better at cooling itself
  Scandinavian Cold Exposure and Immune System

• Scandinavians have a tradition of exposing themselves to cold temperatures 
  • Believed to increase resilience to cold and improve immune system
  • Babies are put outside to sleep in cold temperatures
  • Children run around in t‑shirts in cold weather to activate brown fat
• Cold water swimming is a popular activity in Scandinavia 
  • Believed to activate metabolism and improve health

Study on Cold Exposure, Sauna, and Brown Fat

• Aimed to explore the effects of cold water swimming on brown fat activation
• Proof of concept study with a small number of participants 
  • Main outcome measured through PET-​​CT scans of brown fat
  • Also looked at white fat through fat biopsies
• First year of the study was observational, with the researcher immersing herself in the winter swimming culture 
  • Gained firsthand experience of the effects of cold exposure
  • Found that initial cold exposure was uncomfortable, but the body adapted over time

Personal Experience with Cold Exposure

• Andrew Huberman practices deliberate cold exposure every morning for 1–2 minutes in a cold plunge 
  • Believes it has positive effects on his mood and energy levels
    Cold Exposure and Health Benefits
• Cold showers and cold plunges can activate the sympathetic autonomic response 
  • Increased blood pressure, heart rate, release of norepinephrine, adrenaline, and dopamine
• Parasympathetic response (calming relaxation) is activated when submerging face or body in cold water 
  • This is known as the diving reflex
  • Slows down oxygen consumption, preserving oxygen to prevent hypothermia
  • Activates serotonin in the brain, promoting mental balance
• Cold exposure can increase energy levels and provide a positive feeling
• Women have more brown fat than men, affecting their response to cold exposure
• Thermocomfortable state differs between genders 
  • Men: 22 degrees Celsius
  • Women: 24 degrees Celsius

Cold Exposure Study

• Proof of concept study with winter swimmers 
  • Participants had been swimming for 2–3 seasons
  • Swam 2–3 times per week, staying in the water for 1–2 minutes
• Study aimed to determine the lowest dose of cold exposure that still provided health benefits

• More research needed on the effects of cold exposure on mental balance and well-​​being
  Winter Swimming Study

• Participants: Winter swimmers with experience

• Activity: Cold water immersion and sauna sessions 
  • 2–3 times per week
  • 3 rounds of cold water immersion (1–2 minutes each) and 2 sauna sessions (10–15 minutes each)
  • Cold water temperature ranged from 2–12 degrees Celsius
  • Sauna temperature around 80 degrees Celsius
• Measurements taken:
  • Brown fat activity using infrared camera and PET MRI scanning
  • Insulin sensitivity and glucose clearance
  • Electromyography of muscles to measure shivering
  • Participants’ perception of cold and comfort

Findings

• Winter swimmers had increased insulin sensitivity 
  • Produced less insulin on all experimental days
  • Faster glucose clearance in the bloodstream after consuming a glucose drink
• Winter swimmers had less vigorous shivering when exposed to cold 
  • Perception of cold was similar between groups, but muscle activation was different
• Brown fat activation was measured during cold exposure and thermocomfortable states 
  • PET MRI scanning used to visualize brown fat in subjects
  • Infrared camera used to measure temperature as an outcome for brown fat activity
• Participants’ comfort levels were measured using a visual analog scale 
  • Scale ranged from 1 (very cold) to 10 (very hot), with 5 being thermocomfortable
  • Participants rated their comfort throughout the study days

Implications

• Regular cold water immersion and sauna sessions may improve insulin sensitivity and glucose clearance
• Winter swimmers may experience less vigorous shivering when exposed to cold
• Brown fat activation can be measured using PET MRI scanning and infrared cameras

• Individual comfort levels and responses to cold and heat exposure may vary
  Cold and Heat Exposure Benefits

• Cold exposure benefits: 
  • Reduced blood sugar
  • More efficient clearance of blood sugar
  • Reduced insulin
  • Improved brown fat distribution and density
• Heat exposure benefits: 
  • Improved cardiovascular health
  • Increased heat shock proteins in cells, which repair cells

Thresholds for Benefits

• Cold exposure:
  • 11 minutes total per week
  • Divided into 2–3 sessions of 1–3 minutes each
• Heat exposure (sauna):
  • 57 minutes total per week
  • Divided into 2–3 sessions of 10–15 minutes each

Other Observations

• Improved sleep quality for cold exposure participants
• Increased comfort in cold environments
• Reduced social anxiety and increased comfort with showing skin

Note: These observations are anecdotal and not part of the main study findings.
Nude Beaches and Winter Swimming Culture

• Nude beaches more common in Europe than the United States
• Winter swimming culture in Denmark has existed for hundreds of years 
  • Oldest winter swimming club in Copenhagen has members swim naked
  • Saunas available for mixed-​​gender and separate-​​gender use
• No difference in cold exposure benefits between wearing a bathing suit or swimming naked 
  • Some people feel more free and in touch with nature when skinny dipping

Clothing Optional Facilities

• Clothing optional facilities are becoming more popular as deliberate cold exposure and sauna use increase 
  • Examples: Archimedes Banya in San Francisco, Spa 88 in New York
• These facilities have a focus on health and wellness, not on nudity

Brown Fat Negative Participant

• One participant in the study had no brown fat 
  • Not obese, as that would have disqualified him from the study
  • Struggled to control shivering during the cooling experiment
  • Blood samples and insulin levels were more similar to the control group
  • Blood glucose clearance was not as fast as other winter swimmers
• This participant was considered an outlier and removed from the analysis

Additional Benefits of Deliberate Cold Exposure

• Cold exposure can help lower inflammation in the body 
  • Measured by IL‑6 and IL-​​10 markers in the study
• Lowering inflammation can help prevent lifestyle diseases like type 2 diabetes
• Also linked to reducing the risk of mental diseases like depression, anxiety, and Alzheimer’s

• Exposure to temperature changes can help the body reset and repair itself
  Cold Exposure and Health

• Modern sedentary lifestyle has made us more temperature comfortable 
  • Obesity increases in the 1980s due to more comfortable lifestyles
• Cold and heat exposure, exercise, and fasting can increase hormetic stress in the body 
  • Helps maintain a natural balance

The Soberg Principle: Ending on Cold

• Ending on cold forces the body to heat up by itself 
  • Activates brown fat and muscles for thermogenesis
  • Exercise for the body continues for hours after cold exposure
  • Increases neurotransmitters and makes brown fat cells more efficient
• Winter swimmers have higher skin temperature compared to control group 
  • More vascular skin due to cold and heat contrast
  • Higher heat loss, but keeps brown fat and muscles activated

Fasted vs. Fed Cold Exposure

• No clear studies on benefits of cold exposure while fasted or fed 
  • More research needed

Cold Exposure for Disease Symptoms

• Raynaud’s syndrome: poor blood flow to extremities, causing coldness and discoloration 
  • No specific studies on cold exposure for Raynaud’s syndrome
  • Logically, exposure to cold and heat could help improve vascularization
• Autoimmune conditions and other diseases: no specific studies on cold exposure benefits 
  • Anecdotal reports of improvements, but more research needed

Practicalities of Deliberate Cold Exposure

• Keeping hands out of cold water or wearing neoprene booties can help with discomfort 
  • Full body still covered in cold receptors for activation
• Back of the head headache during cold immersion
  
  Cold Exposure in Children and Gender Differences

• Children and cold exposure: 
  • Children are smaller in mass, so protocols for adults may not directly apply to them
  • One study compared heat loss in 12-​​year-​​old boys and adult men during cold exposure 
    • Boys could defend their core temperature similarly to adults, but had to use their muscles faster
    • They could handle cold exposure for about 1 minute, but would be colder when coming out due to their smaller mass-​​to-​​surface ratio
  • Children can defend their temperature for a shorter time and are at a higher risk of hypothermia
  • It’s important to approach cold exposure with caution for children, starting with cold showers and gradually progressing to cold immersion
• Male and female differences in cold exposure: 
  • There may be differences in how men and women respond to cold exposure, but more research is needed to fully understand these differences
  • Some studies suggest that women may have a higher tolerance for cold exposure due to higher body fat percentages, which can provide insulation
  • Other studies indicate that men may have a greater ability to generate heat through shivering and non-​​shivering thermogenesis
  • It’s important for individuals to listen to their own bodies and adjust their cold exposure practices accordingly, regardless of gender
    Differences in Cold Exposure for Men and Women
• Women have more brown fat and increased metabolism in their brown fat 
• Cold exposure, such as winter swimming with the 11-​​minute protocol, can be beneficial for women as well
• Differences in men and women may affect how long they can stay in cold water without getting hypothermic

Cold Exposure Protocol

• Short, frequent exposures to cold are more beneficial than longer, less frequent exposures
• Changing temperatures during a session can strengthen cells and create hormetic stress
• Keeping the body’s temperature system off balance helps keep it tuned

Circadian Time and Cold Exposure

• Body temperature changes throughout the day, affecting cold exposure benefits
• Going from warm to cold and from cold to warm is more important than the specific temperature or duration of exposure
• Varying temperatures during cold exposure can help keep the body’s system off balance and tuned

Ongoing Study on Cold Exposure

• A new study is being conducted on both men and women, but the data and results are still in preliminary analysis
• The study aims to provide more information on the effects of cold exposure on both genders