January 24, 2023
With ten pale, blue fingers, I white-knuckled the steering wheel of my Toyota RAV4 and strained to remember how to turn on the engine.
After staring blankly through the windshield at the parking lot for several minutes–teeth chattering and brain slowly coming back to life–I leaned to the right, fumbled for the keys that lay on the passenger seat, then cursed as my large intestine contracted and filled my soggy Speedo with a liquid bowel evacuation.
Just ten minutes earlier, I’d dragged my sorry ass out of the frigid Spokane river and stumbled like a drunk, waterlogged sea otter up across the pavement back to my Toyota. See, after studying up on the benefits of cold thermogenesis and practicing cold showers and ice baths for several weeks, I figured I’d level up a notch and try a true cold water swim in the middle of March, when chunks of ice still floated down the Spokane river near my home.
But rather than simply dipping in and out of the safe edges of the water, like a true, hard-charging overachiever, I’d donned nary a shred of clothing and attempted to swim upstream for a good twenty minutes. And now, as my body fought to restore its normal temperature after my foolhardy attempt at a health hack, I was paying the price.
…a long, frigid, lose-control-of-your-bowels ice water swim – like the one I experienced here over fifteen years ago early on in my triathlon training adventures – is not necessary (and, in fact, ill-advised) to take full advantage of the benefits of cold thermogenesis, which include not only a restoration of blood-brain barrier health but increased cell longevity, a robust immune system, rapid fat loss in the absence of exercise, and many of the other benefits I’ve discussed in the plethora of cold thermogenesis articles and podcasts I've released.
Since this is a “hot” topic in health and wellness lately, I thought it was time to give you a comprehensive, updated guide to cold thermogenesis, which I'm publishing as a three-part series. This first article will go over the science behind five major health benefits of cold exposure. Then, I’ll in Part 2, I’ll share with you best practices for getting chilly, and finally, in Part 3, I’ll introduce you to five different options for home cold tubs, including full blueprints and instructions.
Enjoy the goosebumps.
5 “Cool” Health Benefits of Cold Thermogenesis
Cold thermogenesis is the practice of intentionally exposing parts of the body to specific levels of cold stress.
Solid research has shown that cold thermogenesis brings a host of health benefits, from increasing metabolism to helping to control blood glucose levels, reducing inflammation, improving sleep and recovery, and potentially fighting certain types of cancer, as well as promoting overall longevity.
From an ancestral or evolutionary standpoint, this makes sense. Your ancestors did not evolve in conditions with temperatures consistently in the 60s and 70s. Constant temperature control is a modern, technological contrivance. Whether it was an asteroid that blocked out the sun and wiped out the dinosaurs, to reports of a flood that left the planet underwater, your ancestors at some point experienced a dark, cold world, some form of an ice age, and a very likely necessity to evolve and even thrive in cold temperatures. Some researchers have even correlated the increase and control of indoor heating to the rise in obesity (and yes, you must keep in mind that correlations should be taken with a grain of salt).
The point here is that your body is arguably not meant to be at a constant, comfortable temperature and that true, optimal health requires at least occasional cold exposure practices.
There are so many health-promoting effects of cold thermogenesis that if I were to write about all of them, this article would be more of a book. So instead, I am going to focus on five distinct benefits of cold thermogenesis: improved brain health, weight loss, immune system enhancement, increased longevity, and boosted mood. Pretty impressive list, right? I have a feeling that by the time you finish reading this article—or maybe even after reading about the first or second health benefit—you’ll be motivated to get that cold tub set up on the back deck, or at least start to finish that morning shower with an icy blast (and remember, I'll cover much more, including cold tub setups, in Parts 2 & 3).
1. Improved Brain Health
If you’ve ever gulped down a milkshake or a Slurpee as a kid, you know what it is (heck, it’s happened to me in adulthood plenty, too).
However, while sudden cold may feel like it makes your brain stop working, when cold exposure is sustained, the brain, in fact, works more efficiently. This impact on brain health is not, in my opinion, talked about enough though it's one of the most consistent and profound physiological responses to cold exposure, particularly if your head is under the water. In a recent study, researchers found a decrease in the risk of depression, dementia, and Alzheimer's in people who regularly swim in cold water.
A primary reason that cold exposure benefits your brain is that it increases catecholamines, hormones released by your adrenal glands in response to physical or emotional stress. The main types of catecholamines are norepinephrine, dopamine, and epinephrine (adrenaline).
Norepinephrine is a hormone and neurotransmitter that is responsible for increased vigilance, focus, attention, and mood. Studies have shown that norepinephrine enables synaptic plasticity, which is an important foundation for learning and memory. Norepinephrine also directly activates self-renewing and multipotent neural precursors, including stem cells, from the hippocampus of adult mice.
Sustained periods of cold exposure are not necessary for the release of norepinephrine. A long-term study found that norepinephrine increased by 200-300% in a group immersed in cold water at 40°F for twenty seconds and a group that practiced whole-body cryotherapy for two minutes at -166°F three times a week for 12 weeks.
Additionally, when exposed to the cold, the body releases cold shock proteins known as RNA binding motif 3 (RBM3), found in the brain, heart, liver, and skeletal muscle. RBM3 is directly linked to the regeneration of synapses in the human brain. Synapses – gaps between neurons through which your neurons communicate – are responsible for normal brain function and memory formation. This effectively means that cold water therapy could decrease the degeneration of your neurons and, therefore, prevent neurodegenerative diseases because it promotes the growth and development of nervous tissue and neurogenesis. As with norepinephrine release, your core body temperature need not be reduced drastically to release RBM3. Research has found that a 2°F reduction in core body temperature is enough to induce cold shock proteins. Interestingly, melatonin may enhance the cold-induced release of RBM3.
So, while feeling sluggish as temperatures drop may make you think your brain is also slowing down, sustained cold exposure can have the opposite effect: it kicks your cognitive functioning into a higher gear.
2. Weight Loss
Ray Cronise, an author and former NASA scientist, started investigating the effects of cold exposure on weight loss and metabolism after learning that Olympic swimmer Michael Phelps ate 12,000 calories daily.
And while Michael Phelps was undoubtedly burning off many, many more calories than an average active adult, 12,000 still seemed implausibly high.
Ray's investigation led to the conclusion that Michael Phelps needed those calories for his body to be able to fight to regulate its temperature when swimming in chilly pools. Then he turned around and tested his theory on himself, finding that deliberate and regular cold exposure allowed him to double his weight loss over six weeks.
Wim Hof, nicknamed “The Iceman” for his ability to withstand extreme cold, has talked at length about the positive effects of cold exposure on weight loss on my podcast and in his materials. He maintains that exposing the body to the cold safely and regularly can increase the metabolic rate by about 16 percent through shivering, your body’s natural way of generating heat.
This increase in metabolic rate is the first type of thermogenesis that occurs when you are exposed to cold. During that process, your body also burns through glucose. When I'm using my continuous blood glucose monitor, I've found that a good 5- to 10-minute cold exposure in the morning is highly effective for controlling my blood glucose the entire day. Part of that is the result of the upregulation of metabolism. Part of it is the upregulation of some of the GLUT4 transporters, the insulin-regulated glucose transporter found primarily in adipose tissues and striated muscle. (If you want to learn more about blood sugar regulation, listen to this podcast: “Everything You’ve Ever Wanted to Know About Blood Sugar & Glucose Monitoring, But Were Afraid To Ask Or Didn’t Realize, With Casey Means Of Levels.“)
When you're shivering and your muscles are contracting, and your body is doing what it can to stay warm, your metabolic rate goes up. However, thermogenesis is also happening on a cellular level – called non-shivering thermogenesis – a metabolic process located primarily in brown adipose tissue. In your body, you have both brown and white fat. Most of your fat is white fat, which, when built up, leads to obesity. Brown fat, on the other hand, breaks down blood sugar and fat molecules. Cold activates a change from white to brown fat, increasing your metabolic rate and promoting a negative energy balance. Brown fat has even been shown to alleviate metabolic complications like 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, had the following to say after conducting two studies on the impact of cold exposure on brown fat:
“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.”
Now, I don't advocate a huge caloric load that you try to offset with cold therapy. However, including it as part of your weight loss strategy is likely to help you reach your goals faster. (If you want to learn more about calorie load, I talk much more about it in this article – specifically, why it's worth paying attention to caloric density along with nutrient density and volume.)
3. Enhanced Immune System
Did your parents ever warn you that going out in the cold would result in catching a cold?
For whatever reason, this is a widespread belief. And it’s not only false, but research has clearly shown that cold exposure benefits your immune system.
Your immune system is fed by your vascular system. So if your vascular system is not functioning optimally, there is a chronic shortage of feeding toward the immune cells. Cold contributes to the optimization of the cardiovascular system.
A large study in the Netherlands found a 29% reduction in sickness for a group that had adopted a 30-day cold shower regimen, compared to a control group. Another study found that repeated cold water immersions by healthy young men activated participants’ immune systems.
A positive immune response was also noted in a study that involved training subjects in exposing themselves to the cold by standing in the snow barefoot for up to 30 minutes, lying bare-chested in the snow for 20 minutes, ice water submersion for several minutes, and hiking up a snowy mountain in only shorts. The result was that the participants who engaged in those practices had significantly higher levels of epinephrine, which led to more anti-inflammatory mediators.
Then, last year, a comprehensive study published in the journal Cell Metabolism looked at the relationship between cold exposure and metabolic health, specifically concerning immunity. The authors concluded that lower environmental temperature markedly ameliorates neuroinflammation and has a positive effect on immunity.
The increase in norepinephrine with cold stress also decreases macrophage inflammatory protein, MIP-1, which is produced by immune cells and can cause conditions like arthritis and other inflammatory-related health problems. So, this also might be why a guy like Wim Hof (and others in a study in the Netherlands) was able to fight off an injection of E. coli bacteria more effectively with cold exposure.
As you age, your immunity weakens and the anatomy of your lymphatic system also changes. This process, known as immunosenescence, increases susceptibility to infection, autoimmune disorders, and cancer in adults over a certain age. A long-term study in which found that three weekly sessions for six weeks increased the number of lymphocytes–white blood cells necessary in fighting off illnesses like cancer. With age, natural T killer cells decrease; however, through regular exposure to colder temperatures, they may increase again and reduce inflammation while strengthening immunity overall.
While there are many ways to improve your immunity – I recently wrote about three in this article –daily cold exposure is a quick, cheap, and effective way to insure yourself against the viruses that seem to be everywhere this time of year (still including, unfortunately, COVID-19).
4. Increased Longevity
If you’ve been following me for a while, you already know that your chronological age (as in, how many years you have been on this earth) has almost nothing to do with your health.
Your biological age – which the length of your telomeres can measure – is what counts.
Telomeres are regions of repetitive DNA sequences located at the end of your chromosomes. They’re instrumental in the process of cell replication. As you age, cells need to reproduce for your body to function and heal, a process that shortens your telomeres, negatively affecting your cells’ ability to divide normally. Those impaired cells – called senescent cells – release inflammatory cytokines (signaling proteins) that can start the aging process. After controlling for multiple confounding variables, a fascinating study in Belgium found that fetuses exposed to colder environments had increased telomere length. (For more on telomere length, including the results of my own testing, you can listen to my podcast with Jason Shelton of Telomere Diagnostics.)
A study in the journal Biogerontology found that fruit flies exposed to mild cold stress live longer. It is also well-established across multiple organisms that a low basal body temperature increases longevity within a species. In addition, brown fat stimulation from cold exposure has been shown to increase several longevity-associated molecules.
Another important factor in longevity is the protein mTOR. The mTOR signaling pathway integrates intracellular and extracellular signals and is a central regulator of cell metabolism, growth, proliferation, and survival. When the mTOR pathway is inhibited, your body can clean out the metabolic “junk” in your cells, a process called cell autophagy. Caloric restriction and intermittent fasting can stimulate this pathway inhibition, and studies have shown that cold exposure can have a similar effect.
The norepinephrine that's released during the cold can inhibit many inflammatory pathways. The reason you have inflammation is it eliminates the initial cause of a cell injury, clears out dead cells and tissues that get damaged from an insult, and then the inflammatory process can initiate tissue repair. When that process runs awry, for instance, because of chronic stress, it's a driver of the aging process and age-related diseases. In fact, low inflammation is the only biomarker that predicts survival and cognitive capabilities across all age groups when you look at centenarians, semi-supercentenarians, and supercentenarians.
Recently, I published a popular two-part article series on biohacking longevity, and I mention cold exposure in both parts. If you want to read up on other ways to lengthen your lifespan, here are those articles:
- Part 1 Of 2: My Top 10 Steps To Biohack Longevity (& How To Get Many, Many Weird Looks From Your Neighbors)
- Part 2 Of 2: My Top 10 Steps To Biohack Longevity (& How To Get Many, Many Weird Looks From Your Neighbors)
5. Boosted Mood
Understandably, the prospect of jumping into an ice-cold tub may not improve your mood when you’re getting started.
However, there has been significant research showing that regular cold exposure can have a substantial positive effect on your mental state.
Interestingly, positive effects on mood have been found after a single cold exposure. When healthy, fit undergraduates were immersed in cold seawater for 20 minutes, there was a significant decrease in reports of depressive symptoms.
As previously discussed, cold exposure also activates the synaptic release of noradrenaline in the brain. Noradrenaline plays a significant role in depression, as it regulates cognition, motivation, and intellect, which are fundamental in social relationships. Social dysfunction is possibly one of the most important factors affecting the quality of life in depressed patients. Additionally, strong evidence correlates dysfunction in the central noradrenergic system with psychiatric disorders contributing to suicide.
A cold shower works similarly to mild electroshock therapy to the sensory cortex. A study in the journal Medical Hypotheses looked at the hypothesis that psychotic symptoms could result from a lifestyle lacking evolutionarily conserved stressors, such as frequent exposure to heat and/or cold, resulting in a lack of “thermal exercise,” which could lead to malfunctioning of the brain. The paper concluded that a cold shower could induce stress-induced analgesia, suppressing psychosis-related neurotransmission.
Another study in Medical Hypotheses looked at how cold showers can be used as a potential treatment for depression due to anti-depressive electrical impulses from peripheral nerve endings to the brain, which are activated when the cold receptors on the skin are stimulated.
Increased physical and psychological resilience, improved energy level and focus, relaxation, better sleep, and more–the benefits of cold exposure that scientists are discovering through their studies reveal an effective resource for improving overall mental health. And in Part 2 of this series, I'll give you pointers on how to make cold exposure more tolerable.
When I was competing in Ironman triathlons worldwide, over a ten- to twelve-year period, I literally amassed thousands of hours of cold water swimming, before cold therapy was a “thing”. At the time, I had no clue that a host of metabolic benefits would remain with me for a lifetime.
Whether in an icy lake or a drafty gym pool, I was freezing my a$* off nearly every day. And again, at the time, I didn’t even realize that I was getting all of the benefits of cold thermogenesis.
I may not have appreciated it back then, but now I love the cold because it invigorates me while significantly improving my state of mind and physical health. While there are many, many health benefits associated with even short cold therapy sessions, here’s a recap of the five that I chose to focus on in this article:
- When exposed to sustained cold exposure, the brain works more efficiently.
- Cold exposure can aid in weight loss and metabolic health, which was discovered after NASA scientist Ray Cronise learned that Olympic swimmer Michael Phelps ate 12,000 calories a day, and concluded that Phelps needed that excess of calories to regulate his body temperature.
- There are also benefits to the immune system with prolonged cold exposure, including significantly higher levels of epinephrine, which leads to more anti-inflammatory mediators.
- After studying fruit flies exposed to mild cold stress, researchers concluded that cold exposure could contribute to increased longevity. Cold exposure also positively affects telomere length and the mTOR signaling pathway, both of which support cell health and longevity.
- Mood may also get a nice boost after being subjected to prolonged cold, with participants in several studies noting a significant decrease in reports of depressive symptoms.
I hope this review presented a solid case for the huge benefits of cold exposure to your overall well-being. Since those early days, freezing my *$! off has been part of my routine, but now more than ever, it’s a staple, no-excuses-for-not-doing-it practice. In Part 2 of this article series, I'll give you an insider look at my own cold thermogenesis routine along with detailed instructions for timing and protocols. Then, if I’ve convinced you that you also need a daily full-body cold immersion, be on the lookout for Part 3, in which I’ll go through many different options (from DIY to top-of-the-line) for getting yourself chilled up at home.
Do you regularly practice incorporating cold thermogenesis into your regular routine? If so, what’s been the most notable health benefit you’ve experienced so far? If not, what are you looking to get out of starting cold therapy? Let’s discuss this in the comments!