Taking the Cold Water Plunge

By Mauro Proença — Jun 04, 2024
It's impossible not to notice the exponential rise in people, posting on social media, plunging into ice-filled bathtubs or extremely cold waters. It's not because they are masochistic, but rather because of the supposed “benefits” that the practice supposedly offers.
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In the past, it was necessary to fill a large container, such as a trash can, with water and ice; today, companies sell a single product — the only difference being a few thousand dollars. Taking the plunge has opened up avenues for profitable businesses. As per a report from January this year:

“The global Cold Plunge Tub Market is anticipated to witness steady growth with a Compound Annual Growth Rate (CAGR) of 4.85%, projecting an increase from US$ 0.35 billion in 2023 to US$ 0.49 billion by the conclusion of 2030.”

As expected, the marketing by most of these manufacturers adheres to a standard logic found in classical pseudosciences:

  • Appeal to testimonies from devout practitioners who enthusiastically endorse the practice. The more famous the practitioner, the better, as it enhances the spread of the message and boosts sales.
  • Utilize scientific terminology to bolster the product’s credibility.
  • Cherry-picking studies to align with the established narrative.
  • Promise a panacea for a myriad of ailments.

Before you take the plunge into the cold, it's essential to note that, aside from reduced muscle pain and inflammation and perhaps an enhanced sense of well-being for some, other health claims lack sufficient scientific backing or reliable studies.

Let’s focus on the true star of our article: Wim Hof, “The Iceman.” He is a motivational speaker, an extreme athlete with numerous Guinness records, and the creator of the, what else, Wim Hof Method (WHM).

The Wim Hof Method:

According to the ebook on his website, Wim states that his method comprises various pillars, each contributing to the success of the practice.

  • Breathing exercises enable practitioners to delve into their inner nature, transforming moments of stress into calm and peace.
  • Exposure to cold helps quiet life's worries and triggers health responses, facilitating the body's self-repair mechanisms.
  • Meditation and stretching exercises aim to center practitioners, allowing for the realignment of mind and body fostering a balanced life.
  • Lastly, a positive mindset and commitment are crucial to sustaining the practice and achieving positive outcomes.

Following the typical pattern of materials that market themselves as "scientific," a plethora of health benefits are claimed, spanning from bolstering the immune system to enhancing creativity. Naturally, there is also a subsection devoted to "Scientific Evidence," where research is showcased that tested the WHM, revealing notable outcomes such as a decrease in the inflammatory response and an elevation in cortisol levels—a hormone linked to stress, immune function, and the inflammatory response.

Nonetheless, it's crucial to approach these findings with a degree of skepticism, given the conflict of interest involving Wim Hof and his team, who stand to profit from online courses, books, instructor training, and in-person events featuring the Iceman himself - where a weekend can fetch more than a thousand dollars.

What Science Says

An article published in 2014 assessed the impact of the training program on the autonomic nervous system and the innate immune response, the rapid reaction not reliant on specialized cells.

The research involved 24 healthy male volunteers with no prior experience in meditation, randomly assigning them to either the intervention group, where they underwent a 10-day training regimen involving meditation, exposure to cold, and breathing techniques, or to the control group. All volunteers were exposed to Escherichia coli following this training period to incite an immunological response. Blood samples, vital signs, symptoms, and cardiorespiratory parameters were assessed

The intervention group, exposed to breathing techniques inducing hyperventilation, an increase in your rate of breathing (respiratory rate), exhibited the following:

  • An increase in blood pH, a decrease in PCO2, and an increase in bicarbonate levels all normal changes associated with an increase in respiratory rate.
  • Rise in epinephrine levels, known for its stimulating effect on the body.
  • Early production of IL-10, a protein possessing anti-inflammatory properties.
  • Fewer symptoms were reported than in the control group.
  • Accelerated normalization of cortisol levels and fever.
  • Diminished intensity of the inflammatory process.

Based on these findings, the authors conclude that this "proof-of-concept" study [1] demonstrates that the sympathetic nervous and immune systems can be voluntarily influenced by practicing relatively quickly and easily learned techniques.

However, the authors acknowledge that the breathing techniques may have caused the increase in epinephrine. Still, they cannot distinguish which exercises were responsible for this result nor whether the other training elements may have affected the innate immune response. The only way to truly determine which measure was responsible for the observed outcome would be to conduct a trial that compares them directly.

Ten years after the previously mentioned study, a systematic review was published, evaluating all available evidence regarding WHM. The researchers focusing on studies published from 2014 to July 2022 identified nine studies that met their requirements. [2]

The authors analyzed physiological outcomes (such as stress and pro/anti-inflammatory responses, among others) and psychological outcomes. They suggest that WHM appears to offer more benefits for stress response and inflammation, with the practice apparently capable of reducing inflammation in both healthy and unhealthy participants without serious adverse events.

Furthermore, the authors conclude that WHM can yield promising immunomodulatory effects but emphasize the necessity for higher-quality research to substantiate this potential. Most importantly, combining cold exposure with the Wim Hof breathing method, as opposed to breathing alone, seems to be the most effective approach to reducing inflammation.

Despite this seemingly positive conclusion, there are specific characteristics observed in the systematic review that should, at the very least, raise significant doubts about its accuracy:

  • Except for one RCT, all others had a "high concern" regarding bias due to the challenge of blinding participants and researchers during the intervention.
  • The studies’ quality was rated as very low.
  • Sample sizes were small, ranging from 15 to 48 participants.
  • Participants were predominantly male (86,4%), limiting the generalizability of the findings to other demographics.
  • Due to the subjective nature of many psychological outcomes, their reliability is difficult to measure.
  • Improvements in patients’ symptoms may result from a placebo effect. 

The Verdict

When practicing the Wim Hof Method with a good dose of common sense ...it doesn't hurt to try. Although the effects on our health wait to be proven, people may feel healthier.”

- Wouter van Marken Lichtenbelt, Ph.D, Department of Human Biology and Movement Sciences, Maastricht University Medical Center

There are numerous claims but limited evidence regarding the Wim Hof Method. It is conceivable that the practice does indeed alleviate inflammatory processes and stress. However, the validity of other purported benefits remains uncertain, and until we have substantial evidence, they should be treated as such.


[1] “Proof-of-concept” studies represent an early step in clinical studies, typically performed on a small scale and designed to identify and provide preliminary evidence of efficacy in some clinically significant outcome.

[2] “Randomized clinical trials (RCTs) and cohort studies published in peer-reviewed journals, conducted in healthy individuals or those with a pre-existing clinical condition, aged over 14 years, and that used the three pillars of the WHM or focused exclusively on the Wim Hof Breathing Method (WHBM).”


Sources: Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. Proc Natl Acad Sci USA. DOI: 10.1073/pnas.1322174111

Does the Wim Hof Method have a beneficial impact on physiological and psychological outcomes in healthy and non-healthy participants? PLoS One. DOI: https://doi.org/10.1371/journal.pone.0286933

Who is the Iceman? Temperature. DOI: 10.1080/23328940.2017.1329001