Can Ice Bath Prevent Illness?
- Thomas P Seager, PhD
- Nov 8
- 10 min read
As soon as you think you might feel sick, boost your immune system with an ice bath.
Vitamin D deficiency is the real cause of colds
I rarely get sick anymore. I've never even had COVID. I was tested seven times as a requirement for my faculty job at Arizona State University, and I had two antibody tests that I paid for myself.
All negative.
It's hard to say why I'm enjoying a more robust immune system, but I'm going to guess that it's the ice baths.
As a kid I was told that if I spent too long outdoors without a hat and mittens, I would "catch a cold." That myth persists to this day, despite evidence to the contrary.
I now know that it's not cold exposure that causes cold and flu season, it's a lack of Vitamin D. That is, outdoor temperatures plunge during winter, but cold temperatures are not directly responsible for the annual spate of seasonal infections. In fact, a regular practice of deliberate cold exposure can be a boost to the immune system. In one study, researchers found that a single hour of whole body immersion in 14C water (57F) was insufficient to elicit an immune response, but after two weeks of plunging three times a week, blood markers associated with immune strength were lifted (Jansky et al. 1996).
The real culprit in cold and flu season is not the cold -- it is a lack of Vitamin D resulting from too little sunshine during the winter. Current recommendations for Vitamin D were incorrectly established at levels just above those required to prevent rickets. A statistical error in the original Vitamin D studies has yet to be corrected (Papadimitriou 2017).
In Re-ordering Autoimmune Disorders I wrote about the essential role that Vitamin D plays in the development and function of the immune system (Holick 2017). A body that is deficient in Vitamin D is more susceptible to:
infectious disease,
osteoporosis (low bone density),
complications in pregnancy,
neurological disorders,
dental caries (cavities),
Type 1 diabetes and other autoimmune disorders, and
cancer.
The evidence with regard to the indispensable role of Vitamin D in immune function is very strong (Adams & Hewison 2008) and it is borne out in seasonal statistics. Figure 2 below shows how influenza infection rates in Norway compare with sun exposure for synthesis of Vitamin D (Juzeniene et al., 2010).
The more sun, the less serious the flu.
At Northern latitudes, when the sun is at its lowest angles in the sky and the days are shortest, the UVB solar radiation that reaches the surface of the Earth is insufficient to stimulate Vitamin D synthesis in the skin. Consequently, most people in the United States suffer from a Vitamin D deficiency in their bloodstream -- especially during winter months.
To make matters worse, the colder temperatures that prevail in winter cause people to cover more of their skin, and to stay indoors more often. In ancient times, our ancestors could still get an immune system boost from winter time cold exposure, but modern environments have created a comfortable existence away from the prophylactic powers of the natural environment by encouraging indoor habitation during winter.
Cold Activation of Brown Fat Makes Vitamin D
As recently as hundred years ago, before hot, running water became ubiquitous in American homes, our ancestors couldn't avoid going outside in the cold during the winter -- even if it was only for brief periods of time (like using an outhouse). While they wouldn't get much sun, they would get some cold.
Now we know that brief cold activation of brown fat stimulates the production of biophotons from the mitochondria in brown fat, making light inside the body. As I wrote in Cold Stimulates Vitamin D Synthesis, some of that biophoton light is in the UVB range. When it intersects cholesterol molecules inside an active brown fat cell, the UVB biophoton breaks open a carbon-carbon bond and converts cholesterol into pre-vitamin D, which is later metabolized into other forms of Vitamin D as the body requires.
Until very recently, there were no studies that show an increase in blood serum levels of Vitamin D resulting from cold exposure. However, a new study of Polish women with multiple sclerosis (MS) has found exactly that (Ptaszek et al. 2025). Compared to control groups of women without MS who did cryotherapy, and women with MS who did not do cryotherapy, the women with MS who got cold experienced a significant boost to blood serum Vitamin D status without making any other changes.
This raises the question of "Why would we see an increase only in the MS patients?" and in this regard I have a hypothesis.
When Vitamin D is synthesized in the skin in response to UVB light, it must travel from the skin throughout the body until it is either stored or used. Nearly all cells have Vitamin D receptors, partly because Vitamin D is not really a "vitamin" at all. It is a hormone, like all the other signaling molecules synthesized in the mitochondria from cholesterol, including sex steroids and catecholamines.
During summer when sunshine is abundant, Vitamin D is produced in excess and stored predominantly inside fat cells, so it must travel from skin to fat. It seems like this shouldn't take very long, but the metabolism of Vitamin D is complex. There are many different forms, and in the bloodstream it is tightly bound to alpha globulin (proteins) that slow its release from the bloodstream for storage in fat cells (Haddad 1979). However, when Vitamin D is synthesized inside brown fat cells in response to cold, it does not need to travel throughout the body in the blood. It's already right where it can be stored until its needed.
In women without MS, the biophoton Vitamin D is likely released from the brown fat cells slowly, as the body needs it. However, women with MS are already suffering from an immune system crisis. It may be that they need the biophoton Vitamin D right away to modulate otherwise aberrant immune function, and thus blood serum levels increase as the biophoton Vitamin D is released immediately.
Support for this hypothesis comes from very recent studies that show Vitamin D supplementation treats symptoms of MS. For example, a Canadian group of neuroscientists wrote that the form of Vitamin D "1,25(OH)2D3 promotes stem cell proliferation and drives the differentiation of neural stem cells into oligodendrocytes, which carry out remyelination" (Sangha et al. 2023). In other words, the active form of Vitamin D3 is capable of reversing the demyelination of nerve structures that is the hallmark of MS.
Why wouldn't a body with MS want that biophoton Vitamin D circulating in the bloodstream right away? Nonetheless, clinical trials in Vitamin D supplementation for MS patients are either inconclusive or discouraging. In one study, treating human MS patients with supplemental Vitamin D failed to result in improvement (Cassard et al. 2023).
There could be several reasons for the failure, but in my view these findings are consistent with other studies that show the Vitamin D your body makes itself is superior to supplements. Except in cases of symptomatic, medical insufficiency, I'm skeptical that Vitamin D supplements are going to realize the same benefits as innate synthesis. That is, I believe that supplements can help rescue patients suffering from symptoms of low Vitamin D. I doubt they're helpful to support people who are otherwise in good health.
One of the great clinical advantages of cold and sun exposure is that they reduce the risk of all types of infections, including the secondary respiratory infections that accompany influenza infection, such as pneumonia. That is, sunshine and cold are good systemic stimulus for the entire body, and support metabolic, sexual, psychological, and neurological health -- not just immune function.
When I first feel the symptoms of some mysterious viral infection, whether that's a sore throat or aches in my joints, I hop into my ice bath to give my immune system a boost. Just one minute at 34F does my body a lot of good. While I might ordinarily do up to four minutes in the ice bath, if I'm feeling run down I think less is more. A brief plunge often clears up the aches and pains, resolves any sore throat, and helps clear my sinuses.
I recently heard from a reader who was struggling to fight off a low-level cold that sapped her energy, gave her a runny nose, and prevented her from being productive. She tried my advice to do a short, cold ice bath and reported back to me the next day that the fog of her illness had lifted, and she felt like her old self again.
That's been my personal experience, too.
Do not treat fevers with pharmaceuticals
I have a different view of ice baths if you are actively experiencing a fever. Here, I suspect that it's better to let the fever run its course. I've even encouraged a fever to advance by wrapping myself up in as many blankets as I've got to trap my body heat and drive my temperature higher.
It is very rare for a natural fever to result in dangerous hyperthermia. Although heat can certainly be hazardous to the brain, a fever is a normal immunological response to infection that your body is well-designed to carry out.
Dr. Suzanna Humphries is one of the most outspoken critics of using drugs to treat fevers. In her view, the fever is how the body responds to infection, and it should be allowed to run its course without chemical interferences. When cooling might be called for, she favors ice baths over pharmaceuticals.
Fever has been one of the great mysteries of metabolism. For decades, medical doctors believed that there was no such thing as brown fat (brown adipose tissue, BAT) in adult human beings. In Thermogenic Foods Activate Brown Fat, I explained the new science of brown fat that corrected that misconception. Nonetheless, it remains the case that only those adults who experience regular cold exposure maintain detectable brown fat. Others seem to lose theirs with age.
Because it is brown fat that is understood to be the primary mechanism of non-shivering thermogenesis, you might think that most adults would be incapable of producing and maintaining a fever during sickness without violent, controllable shivering to produce enough heat to elevate body temperature. But you'd obviously be wrong.
How then could a body produce a fever without shivering?
Recently, some researchers have become convinced that non-shivering thermogenesis can also occur in muscles -- not just brown fat (Bal et al. 2020, Nowack et al. 2027). For example, University of Sherbrooke Professor Denis Blondin, who is one of the world's foremost experts on brown fat, told me that there just isn't a large enough quantity of it in cold-adapted human beings to account for all the thermogenesis he's observed in his subjects when exposed to cold. Muscle, on the other hand, is much more plentiful. Therefore, non-shivering thermogenesis could be a secondary function of muscle tissue that becomes the source of heat necessary to elevate body temperature and fight infection.
Use ice baths to treat hyperthermia, not fever
Most parents seek treatment and most pediatricians oblige with advice to take chemical fever-reducers for children experiencing fevers (Vicens‐Blanes 2023) -- exactly what Dr. Suzanne Humphries advises against. Chemical fever reducers might make a patient more comfortable and parents less anxious, but they also engender unjustified risks to the gastrointestinal tract, the liver, and the brain.
One of the big differences between pharmaceutical treatment of a fever and whole-body cold water immersion for treating hyperthermia is that the chemicals shut down thermogenesis, while the ice bath accelerates it. This may be another reason why Dr. Humphries prefers ice baths to Tylenol.
The ice bath reduces core body temperature in a patient experiencing hyperthermia, without shutting down the thermogenic immune response. In this way, the mitochondria keep working, without creating excess temperatures that could damage the brain.
If your illness has progressed to the point of fever, there's likely little harm in doing a short session in your ice bath -- if you can stand it. You will likely experience some relief from inflammation and you may feel more comfortable, but I doubt it's going to speed healing. Unless your body temperature reaches a level that your physician considers dangerous, perhaps above 104F in adults or 106F in children (consult your doctor), I'm not encouraging anyone in the throws of full-blown infectious disease to do an ice bath.
However, the next time I do get sick, as I'm sure it must happen sometime, I'll run an experiment on myself and I'll let you know what happens to me.
References
Adams JS, Hewison M. Unexpected actions of vitamin D: new perspectives on the regulation of innate and adaptive immunity. Nature clinical practice Endocrinology & metabolism. 2008 Feb;4(2):80-90.
Bal NC, Periasamy M. Uncoupling of sarcoendoplasmic reticulum calcium ATPase pump activity by sarcolipin as the basis for muscle non-shivering thermogenesis. Philosophical Transactions of the Royal Society B. 2020 Mar 2;375(1793):20190135.
Cassard SD, Fitzgerald KC, Qian P, Emrich SA, Azevedo CJ, Goodman AD, Sugar EA, Pelletier D, Waubant E, Mowry EM. High-dose vitamin D3 supplementation in relapsing-remitting multiple sclerosis: a randomised clinical trial. EClinicalMedicine. 2023 May 1;59.
Haddad Jr. JG. Transport of vitamin D metabolites. Clinical Orthopaedics and Related Research®. 1979 Jul 1(142):249-61.
Holick MF. The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Reviews in endocrine and metabolic disorders. 2017 Jun;18(2):153-65.
Janský L, Pospíšilová D, Honzova S, Uličný B, Šrámek P, Zeman V, Kaminkova J. Immune system of cold-exposed and cold-adapted humans. European journal of applied physiology and occupational physiology. 1996 Mar;72(5):445-50.
Juzeniene A, Ma LW, Kwitniewski M, Polev GA, Lagunova Z, Dahlback A, Moan J. The seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin D. International Journal of Infectious Diseases. 2010 Dec 1;14(12):e1099-105.
Nowack J, Giroud S, Arnold W, Ruf T. Muscle non-shivering thermogenesis and its role in the evolution of endothermy. Frontiers in physiology. 2017 Nov 9;8:889.
Papadimitriou DT. The big vitamin D mistake. Journal of preventive medicine and public health. 2017 May 10;50(4):278.
Ptaszek B, Podsiadło S, Czerwińska-Ledwig O, Teległów A. Whole-Body Cryotherapy Affects Blood Vitamin D Levels in People with Multiple Sclerosis. Journal of Clinical Medicine. 2025 Apr 29;14(9):3086.
Sangha A, Quon M, Pfeffer G, Orton SM. The role of vitamin D in neuroprotection in multiple sclerosis: an update. Nutrients. 2023 Jun 30;15(13):2978.
Rheem DS, Baylink DJ, Olafsson S, Jackson CS, Walter MH. Prevention of colorectal cancer with vitamin D. Scandinavian journal of gastroenterology. 2010 Aug 1;45(7-8):775-84.
Vicens‐Blanes F, Miró‐Bonet R, Molina‐Mula J. Analysis of the perceptions, knowledge and attitudes of parents towards fever in children: A systematic review with a qualitative meta‐synthesis. Journal of Clinical Nursing. 2023 Apr;32(7-8):969-95.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University and CEO of the Morozko Forge ice bath company. Seager is an expert in the use of ice baths for building metabolic and psychological resilience.
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