How to Use Cold & Heat Exposure to Improve Your Health | Dr. Susanna Søberg
Dr. Susanna Søberg, PhD, discusses her research on deliberate cold and heat exposure, explaining how these protocols improve metabolism, cardiovascular and brain health, balance hormones, and decrease inflammation. She provides actionable tools and answers common questions about using cold and heat for health.
Deep Dive Analysis
17 Topic Outline
Initial Physiological Response to Uncomfortably Cold Environments
Gauging Cold Exposure Discomfort and Duration
Cold Showers, Immersion, and Brown Fat Activation Pathways
Understanding Shivering, Afterdrop, and Healthy Stress (Hormesis)
Long-Term Health Benefits: Blood Pressure, Insulin Sensitivity, Metabolism
Brown Fat Plasticity, Distribution, and Temperature Regulation
Cultural Cold Adaptation and Resilience in Scandinavia
The Diving Reflex and Parasympathetic Activation
Dr. Søberg's Landmark Study: Design and Methodology
Minimum Thresholds for Deliberate Cold and Sauna Benefits
Maintaining Stimulus and Avoiding Over-Adaptation
Subjective Effects: Sleep Quality and Comfort Levels
Case Study: "Brown Fat Negative" Individual and Shivering Response
Cold and Heat for Systemic Inflammation Reduction
The Søberg Principle: Ending Cold Exposure with Cold
Practical Considerations: Raynaud's, Headaches, Children, Gender Differences
Optimizing Adaptation Through Brief, Repeated Temperature Changes
9 Key Concepts
Sympathetic Nervous System
The branch of the nervous system responsible for increasing heart rate, alertness, and the stress response, also active when waking up.
Catecholamines
A group of neurotransmitters including dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline), which are released during cold exposure and impact mood, energy, and metabolism.
Cold Shock
The rapid physiological response to sudden cold exposure, characterized by hyperventilation, increased breathing rate, and activation of the sympathetic nervous system and catecholamines.
Brown Fat (BAT)
A healthy type of fat tissue rich in mitochondria that acts as the body's primary responder to cold, increasing metabolism and heat production to maintain core temperature. It is an insulin-sensitive organ that can grow and decrease in response to cold exposure and noradrenaline.
After Drop
A phenomenon where the body's core temperature continues to decrease even after exiting cold water, occurring as constricted blood vessels dilate and cold blood from the periphery returns to the core.
Hormesis
The concept of healthy stress, where exposing cells to mild, transient stressors like exercise, cold, or heat makes them more robust, efficient, and better able to activate, increasing their resilience.
Insulin Sensitivity
The body's ability for cells to respond effectively to insulin, allowing for efficient uptake of glucose from the bloodstream. Improved insulin sensitivity is a beneficial outcome of deliberate cold exposure, helping prevent lifestyle diseases like type 2 diabetes.
Diving Reflex
A survival mechanism activated upon submersion in cold water, which slows down oxygen consumption and heart rate to help preserve oxygen and prevent rapid hypothermia.
Søberg Principle
The practice of ending deliberate cold exposure sessions on cold, rather than warming up immediately, to force the body to generate its own heat, thereby keeping brown fat and muscles activated for hours and further boosting metabolism.
10 Questions Answered
The water should be uncomfortably cold enough to induce a 'cold shock' and activate the sympathetic nervous system, but the exact temperature can vary based on individual adaptation and should be balanced with duration.
Long-term benefits include lower blood pressure, lower resting heart rate, improved insulin sensitivity, better glucose balance, and reduced systemic inflammation, which can help prevent lifestyle diseases.
Yes, brown fat is very plastic and can grow and increase its mitochondrial density in response to consistent cold exposure, such as sleeping in a cool room, going outside in cold air, or regular cold water immersion.
To maximize health benefits, it's important to maintain the stimulus of cold shock by keeping sessions relatively short and frequent, rather than becoming so cold-adapted that the exposure no longer feels challenging.
Children are at a greater risk of hypothermia due to their smaller body mass and larger surface area to volume ratio, meaning they can be in cold water for less time than adults before getting too cold. Caution and shorter durations are advised.
Women generally have more brown fat and tend to be physically colder than men. While current short, micro-stressing protocols are likely beneficial for both, future research may reveal optimal differences, especially for longer durations.
Ending on cold (the Søberg Principle) is recommended because it forces the body to generate its own heat, keeping brown fat and muscles activated for hours, boosting metabolism, and enhancing the adaptive response.
Submerging the head significantly increases heat loss from the body's core (by 36% compared to neck immersion), bringing one closer to hypothermia and potentially increasing the after-drop effect. Wearing a cap can help mitigate heat loss from the head.
While specific studies are needed, logically, gradual exposure to cold and heat might help improve vascularity. However, individual experiences vary, and it's recommended to protect hands and feet with neoprene if pain is a barrier.
There are currently no specific studies that directly compare the benefits of deliberate cold exposure when fasted versus after a meal.
20 Actionable Insights
1. Minimum Cold Exposure Protocol
Engage in deliberate cold exposure for 1-2 minutes per session, 2-3 times per week, totaling 11 minutes per week. This duration is sufficient to activate brown fat, increase metabolism, and improve insulin sensitivity.
2. Minimum Heat Exposure Protocol
If combining with cold, use sauna for 10-15 minutes per session, 2-3 times per week, totaling 57 minutes per week. This duration is effective for cardiovascular health and cellular repair, and going beyond 30 minutes per session does not yield additional health benefits.
3. The Soberg Principle: End on Cold
Always conclude your cold/heat alternation with cold exposure. This forces your body to heat up by itself, extending metabolic activation, neurotransmitter release, and brown fat efficiency for hours after the session.
4. Embrace Cold Discomfort & Shivering
Actively seek uncomfortable cold that induces a ‘cold shock’ (e.g., initial hyperventilation) and allow yourself to shiver. This ‘healthy stress’ (hormesis) trains cells, boosts metabolism, and enhances insulin sensitivity, leading to long-term health improvements.
5. Vary Temperature Stimuli
Intentionally vary the temperature of your cold exposure or alternate between cold and heat. This continuous challenge keeps your body’s cells robust and adaptive, preventing over-adaptation and maintaining the hormetic stress response.
6. Hydrate with Electrolytes Daily
Dissolve one packet of electrolyte mix (sodium, magnesium, potassium, no sugar) in 16-32 ounces of water first thing in the morning and during physical exercise. This is critical for optimal brain and body function.
7. Utilize NSDR/Yoga Nidra for Energy
Practice Non-Sleep Deep Rest (NSDR) or Yoga Nidra, even for short 10-minute sessions, to significantly restore cognitive and physical energy.
8. Sleep in a Cool Environment
Maintain a room temperature of approximately 19°C (66°F) while sleeping. This activates and helps grow brown fat, which can improve insulin sensitivity and overall metabolism.
9. Wear Fewer Layers for Cold Adaptation
In colder weather, intentionally wear fewer layers of clothing (e.g., a t-shirt) to expose your skin to cold. This activates brown fat and builds resilience to cold, enhancing your body’s natural heating mechanisms.
10. Prioritize Cold Water Immersion
Submerging most of your body in cold water (up to the neck) provides a more potent activation of cold receptors and the nervous system compared to cold air or showers, leading to greater physiological benefits.
11. Time Cold Exposure Flexibly
Perform deliberate cold exposure when it fits your schedule. If done in the evening, monitor its impact on your sleep quality and adjust if necessary, as it activates the sympathetic nervous system.
12. Children’s Cold Exposure Caution
Children require significantly shorter cold exposure durations than adults due to their smaller body mass, which makes them more susceptible to hypothermia.
13. Avoid Head Submersion in Cold Water
Do not dunk your head in very cold water, as it drastically increases heat loss (by 36% from the core) and decreases blood flow to the brain, elevating the risk of hypothermia and the ‘after-drop’ phenomenon.
14. Wear a Beanie in Cold Water
When immersing in cold water up to the neck, wear a beanie to prevent dizziness, brain freeze, and reduce heat loss from the head, allowing for a more comfortable and potentially longer safe exposure.
15. Manage Extremity Pain
If cold exposure causes intense pain in your hands or feet, keep them out of the water or use neoprene booties. This allows you to still gain full-body benefits without the barrier of localized pain.
16. Submerge Fully (Excluding Head)
To minimize discomfort at the water’s surface interface, submerge your entire body (up to the neck) rather than partial immersion.
17. Cold/Heat Lowers Inflammation
Deliberate cold and heat exposure are effective in lowering systemic inflammation, which can help prevent various lifestyle diseases and improve mental health conditions like depression and anxiety.
18. Cold Exposure for Mental Well-being
Cold exposure activates the parasympathetic nervous system and increases neurotransmitters like serotonin, contributing to improved mental balance, positive mood, and anecdotally, reduced social anxiety.
19. Clothing Optional, Benefits Unchanged
Whether you wear a bathing suit or are naked during cold water exposure does not affect the physiological benefits. The choice is personal and cultural.
20. Cold Exposure for Raynaud’s
While not scientifically proven, some individuals with Raynaud’s syndrome report that regular cold and heat exposure helps improve their symptoms, potentially by improving vascular elasticity, but more studies are needed.
6 Key Quotes
If you enjoy it, then yeah, then I'm thinking something is wrong. It's not right. You should not enjoy it.
Susanna Søberg
The more you avoid the cold, the more painful it will feel when you go into it.
Susanna Søberg
It's just like seeing shivering as a way of your body, it's training, it's training for all your cells, it's training for your muscles, it's training of your metabolism.
Susanna Søberg
The more discomfort, provided it's done safely, just like with exercise, the more shivering, the more cold shock... it sounds like all of that is going to set in motion some long-term changes that will make people feel better and will improve health.
Andrew Huberman
If you really dread the cold and don't like the cold, then you are a perfect candidate for using deliberate cold exposure.
Susanna Søberg
Biology is not an event, it's a process.
Andrew Huberman
2 Protocols
Dr. Søberg's Deliberate Cold and Sauna Protocol (Minimum Effective Dose)
Susanna Søberg- Engage in cold water immersion (2-12 degrees Celsius) for 1-2 minutes per dip.
- Follow with a sauna session (around 80 degrees Celsius) for 10-15 minutes.
- Repeat this cycle for a total of 3 cold dips and 2 sauna sessions per outing.
- Always end the session with cold exposure.
- Perform these sessions 2-3 times per week.
General Cold Adaptation and Maintenance Protocol
Susanna Søberg- Begin by gradually exposing yourself to cold, such as going outside in a t-shirt or sleeping in a cool room (e.g., 19 degrees Celsius).
- Progress to cold showers or cold plunges as comfort and adaptation increase.
- Aim for short, repeated exposures (e.g., 1-2 minutes per cold dip) to maintain the 'cold shock' stimulus.
- Vary the temperature of your cold exposure over time to keep your body's cells challenged and adaptive.
- Always conclude any cold and heat alternation with cold exposure to promote natural body heating and metabolic activation.