Cold thermogenesis involves intentionally exposing parts of the body to specific levels of cold stress.
Numerous studies have demonstrated the myriad health benefits of cold thermogenesis. These include increased metabolism, better blood glucose control, reduced inflammation, improved sleep and recovery, potential cancer-fighting effects, and overall promotion of longevity.
From an evolutionary perspective, this approach aligns with our ancestral heritage. Our predecessors did not experience consistently mild temperatures like those controlled by modern technology. Throughout history, there have been periods of darkness, cold, and ice ages, during which our ancestors had to adapt and thrive in cold environments.
Interestingly, some researchers have linked the rise in indoor heating and the decrease in cold exposure to the increase in obesity rates (though it's important to consider correlations with caution).
This suggests that our bodies are not designed to be constantly kept at a comfortable temperature and that occasional cold exposure is crucial for optimal health.
The benefits of cold thermogenesis are extensive, and covering all of them would require a book-length article. Instead, let's focus on five specific advantages: improved brain health, weight loss, immune system enhancement, increased longevity, and boosted mood. Quite an impressive array, isn't it? By the time you finish reading this article, you may find yourself motivated to set up a cold tub on your back deck or incorporate an icy blast into your morning shower.
Ever experienced brain freeze from gulping down a cold milkshake or Slurpee? It's a familiar sensation, even in adulthood. However, when cold exposure is sustained, the brain actually becomes more efficient, contrary to the temporary feeling of cognitive impairment. Surprisingly, the impact of cold on brain health is often overlooked, despite being one of the most consistent and profound physiological responses to cold exposure, especially when the head is submerged in water. A recent study even found a reduced risk of depression, dementia, and Alzheimer's among individuals who regularly swim in cold water.
Cold exposure benefits the brain in several ways, and one key factor is the increase in catecholamines. These hormones are released by the adrenal glands in response to physical or emotional stress. The main types of catecholamines are norepinephrine, dopamine, and epinephrine (adrenaline).
Norepinephrine, a hormone and neurotransmitter, plays a vital role in boosting vigilance, focus, attention, and mood. Studies have demonstrated that norepinephrine promotes synaptic plasticity, which is essential for learning and memory. It also directly activates neural precursors, including stem cells, in the hippocampus of adult mice.
Long periods of cold exposure are not necessary to trigger the release of norepinephrine. In a long-term study, norepinephrine levels increased by 200-300% in individuals immersed in 40°F cold water for twenty seconds or those practicing whole-body cryotherapy at -166°F for two minutes, three times a week, over a 12-week period.
Dopamine also plays a critical role in cognitive function, while epinephrine enhances learning and memory processing.
Furthermore, cold exposure prompts the release of cold shock proteins called RNA binding motif 3 (RBM3) in the brain, heart, liver, and skeletal muscle. RBM3 is closely linked to synapse regeneration in the human brain. Synapses are the gaps between neurons that facilitate communication and are essential for normal brain function and memory formation. Consequently, cold water therapy may reduce neuronal degeneration and help prevent neurodegenerative diseases by promoting the growth and development of nervous tissue and neurogenesis. Notably, a drastic reduction in core body temperature is unnecessary to trigger the release of RBM3. Research has shown that a mere 2°F decrease is sufficient to induce cold shock proteins. Interestingly, melatonin may enhance the release of RBM3 induced by cold.
So, despite the initial sluggishness that may accompany dropping temperatures, sustained cold exposure can actually elevate cognitive functioning to a higher level.
The effects of cold exposure on weight loss and metabolism were investigated by Ray Cronise, a former NASA scientist, inspired by the astonishing calorie intake of Olympic swimmer Michael Phelps, who consumed 12,000 calories daily.
Cronise hypothesized that Phelps needed those calories to regulate his body temperature while swimming in cold pools. To test his theory, Cronise subjected himself to deliberate and regular cold exposure and found that it doubled his weight loss over a six-week period.
Wim Hof, known as "The Iceman" for his ability to withstand extreme cold, has also discussed the positive impact of cold exposure on weight loss. He suggests that safe and regular cold exposure can increase the metabolic rate by approximately 16% through shivering, the body's natural mechanism for generating heat.
The increase in metabolic rate is the initial type of thermogenesis that occurs during cold exposure. This process also leads to the burning of glucose. Personal experimentation with a continuous blood glucose monitor has shown that a 5- to 10-minute cold exposure in the morning effectively controls blood glucose levels throughout the day. This can be attributed to metabolic upregulation and the activation of insulin-regulated glucose transporters known as GLUT4 transporters, primarily found in adipose tissues and striated muscle.
When shivering and muscle contractions occur to maintain warmth, the metabolic rate increases. Additionally, non-shivering thermogenesis takes place at the cellular level, primarily in brown adipose tissue. The body contains both white and brown fat, with white fat contributing to obesity when accumulated. Brown fat, however, aids in the breakdown of blood sugar and fat molecules. Cold exposure triggers the conversion of white fat to brown fat, boosting metabolic rate and promoting a negative energy balance. Research has even shown that brown fat can alleviate metabolic complications such as high cholesterol, impaired insulin secretion, and insulin resistance in type 2 diabetes.
Yu-Hua Tseng, Ph.D., a senior investigator at Joslin Diabetes Center and professor of medicine at Harvard Medical School, conducted studies on the impact of cold exposure on brown fat and stated:
"We discovered that cold exposure reduced inflammation and improved metabolism in obesity, mediated at least in part by the activation of brown adipose tissue. These findings suggest a previously unrecognized function of brown adipose tissue in promoting the resolution of inflammation in obesity."
While I do not advocate compensating for a large caloric load through cold therapy, incorporating it as part of a weight loss strategy can help achieve goals more effectively. (For further information on calorie load and considerations, please refer to the article discussing caloric density, nutrient density, and volume.)
The belief that going out in the cold leads to catching a cold is a widespread misconception, as research has actually shown that cold exposure benefits the immune system.
The immune system relies on the vascular system for nourishment. When the vascular system functions optimally, immune cells receive sufficient nourishment. Cold exposure contributes to the optimization of the cardiovascular system.
A study conducted in the Netherlands revealed a 29% reduction in sickness among individuals who adopted a 30-day cold shower routine compared to a control group. Another study involving healthy young men found that repeated cold water immersions activated the participants' immune systems.
Positive immune responses were observed in a study where subjects exposed themselves to cold by standing barefoot in the snow, lying bare-chested in the snow, submerging themselves in ice water, and hiking up snowy mountains in shorts. The participants who engaged in these practices exhibited significantly higher levels of epinephrine, leading to increased production of anti-inflammatory mediators.
Furthermore, a comprehensive study published in the journal Cell Metabolism investigated the relationship between cold exposure and metabolic health, particularly regarding immunity. The study concluded that lower environmental temperatures greatly reduce neuroinflammation and have a positive impact on immunity.
Cold stress increases norepinephrine levels, which, in turn, decrease the production of macrophage inflammatory protein (MIP-1). MIP-1 is produced by immune cells and can contribute to conditions like arthritis and other inflammatory-related health issues. This may explain why individuals like Wim Hof and participants in a Netherlands study were able to effectively combat an injection of E. coli bacteria through cold exposure.
As you age, your immunity weakens, and changes occur in the anatomy of your lymphatic system. This process, known as immunosenescence, increases vulnerability to infections, autoimmune disorders, and cancer in older adults. A long-term study demonstrated that three weekly sessions of cold exposure for six weeks increased the number of lymphocytes, which are white blood cells crucial for fighting illnesses like cancer. Regular exposure to colder temperatures can potentially restore the decrease in natural T killer cells associated with aging, reducing inflammation and strengthening overall immunity.
While there are various methods to enhance immunity, daily cold exposure offers a quick, affordable, and effective way to protect yourself against viruses that are prevalent, including COVID-19.
While the idea of immersing yourself in icy-cold water may not initially sound appealing, research has shown that regular cold exposure can have a significant positive impact on your mental well-being.
Fascinatingly, even a single cold exposure session has been found to improve mood. A study involving healthy and physically fit undergraduates found that immersing them in cold seawater for 20 minutes led to a significant decrease in depressive symptoms.
As mentioned earlier, cold exposure triggers the release of noradrenaline in the brain, which plays a crucial role in regulating cognition, motivation, and intellect, all of which are essential for healthy social relationships. Impaired functioning of the central noradrenergic system has been linked to psychiatric disorders associated with suicide. Therefore, activating the release of noradrenaline through cold exposure can be beneficial for mood management.
Cold showers have been compared to mild electroshock therapy for the sensory cortex. A study published in the journal Medical Hypotheses proposed that a lack of evolutionarily conserved stressors, such as regular exposure to heat and cold, could lead to malfunctioning of the brain and contribute to psychotic symptoms. The study concluded that cold showers could induce stress-induced analgesia, which suppresses psychosis-related neurotransmission.
Furthermore, another study in Medical Hypotheses explored the potential of cold showers as a treatment for depression. Cold receptors on the skin, when stimulated, activate peripheral nerve endings that transmit anti-depressive electrical impulses to the brain.
Your health is not solely determined by your chronological age, but rather by your biological age, which can be measured by the length of your telomeres.
Telomeres are repetitive DNA sequences located at the ends of your chromosomes, playing a vital role in cell replication. As you age, the process of cell reproduction causes your telomeres to shorten, negatively impacting the normal division of cells. Senescent cells, which are impaired cells, release inflammatory cytokines that contribute to the aging process. Intriguingly, a study conducted in Belgium found that fetuses exposed to colder environments had increased telomere length, highlighting the potential link between cold exposure and longevity.
Research in the journal Biogerontology has demonstrated that fruit flies exposed to mild cold stress tend to have longer lifespans. This phenomenon of increased longevity with lower basal body temperature is well-established across various organisms. Additionally, cold exposure stimulates brown fat activation, which has been shown to enhance several longevity-associated molecules.
The protein mTOR is another crucial factor in promoting longevity. The mTOR signaling pathway acts as a central regulator of cell metabolism, growth, proliferation, and survival. When the mTOR pathway is inhibited, a process called cell autophagy occurs, allowing your body to eliminate metabolic waste in cells. Caloric restriction and intermittent fasting can trigger this inhibition of the mTOR pathway, and studies have indicated that cold exposure can have a similar effect.
Cold exposure induces the release of norepinephrine, which can inhibit inflammatory pathways. Inflammation serves to eliminate initial causes of cell injury, clear damaged cells and tissues, and initiate tissue repair. However, when inflammation becomes dysregulated due to chronic stress, it becomes a driver of the aging process and age-related diseases. Interestingly, low inflammation is the only biomarker that predicts survival and cognitive capabilities across different age groups, including centenarians and supercentenarians.
Understanding these mechanisms and their impact on longevity emphasizes the potential benefits of cold exposure for promoting a longer and healthier life.