While Others Spread Myths, Kairos Shares Science: The Truth About Cold Plunge and Vitamin D

The Problem with Single-Study Social Media Posts

As someone with a PhD in Physiology and a wellness business owner, I exist in both worlds—the rigorous scientific community and the enthusiastic wellness industry. I appreciate when wellness professionals try to share research with their communities. It shows curiosity and a desire to provide evidence-based services.

However, when I see wellness businesses sharing online articles about single scientific studies—especially with interpretations that don't match what the research actually says—it raises significant red flags among scientists. This isn't just pedantic nitpicking; it's about protecting public health, maintaining industry credibility, and serving our clients with integrity.

Let me walk you through a recent example that perfectly illustrates why this matters.

The Case: Cold Plunge and Vitamin D- Science

Recently, a wellness business posted that a research article "demonstrates cold plunge increases vitamin D." This claim caught my attention immediately because it's physiologically impossible—vitamin D requires UVB radiation from sunlight to be synthesized in the skin. Cold water provides no UVB rays.

When I read the actual study, my concerns multiplied. Here's what the research actually showed:

What This Study Actually Examined

Study: "Impact of Chronic Cold Water Immersion and Vitamin D3 Supplementation on the Hippocampal Metabolism and Oxidative Stress in Rats" (Korewo-Labelle et al., 2025)

This research examined chronic cold water stress in rats to see if vitamin D supplementation could protect the brain from stress-induced damage.

Let's break down the critical methodological issues:

Critical Issue 1: This Was NOT Cold Plunge Therapy

• Water depth: 1 cm (0.4 inches) - rats stood in shallow water, not immersion

• This is fundamentally different from the full-body submersion in cold plunge therapy

• 28 consecutive days of daily exposure = chronic stress model, not therapeutic use

Critical Issue 2: Severely Underpowered Study

• Control group: n=4

• Treatment groups: n=6-8

• Western blot analysis: n=2-3

• These sample sizes are far too small to draw reliable conclusions

Critical Issue 3: The Vitamin D Misinterpretation

Here's where the interpretation went completely wrong:

• What the study did: Researchers gave rats oral vitamin D3 supplements (600 IU/kg/day) to test whether supplementation could protect against cold stress-induced brain damage.

• What the study found: Vitamin D supplementation provided only minimal protection and did not prevent hippocampal atrophy or restore most stress markers to normal levels.

• What the study did NOT show: That cold water exposure increases vitamin D levels.

  
  

In fact, the authors explicitly stated:

"serum vitamin D3 concentration and metabolites remained unchanged after 28 days of CCWI"

The study measured vitamin D as an intervention, not as an outcome of cold exposure.

Key conclusions from the authors:

"Although vitamin D3 did not prevent structural changes, it improved mitochondrial enzyme activity and modulated oxidative stress parameters"

"Overall, the neuroprotective effect of vitamin D3 in this model remained limited."

The Fundamental Science: Why Cold Water Cannot Increase Vitamin D

Vitamin D synthesis requires a specific biochemical pathway:

1. UVB radiation (290-320 nm wavelength) from sunlight penetrates the skin

2. UVB photons convert 7-dehydrocholesterol in the skin to previtamin D3

3. Body heat isomerizes previtamin D3 to vitamin D3 (cholecalciferol)

4. The liver and kidneys convert it to active forms (25-hydroxyvitamin D and 1,25-dihydroxyvitamin D)

Cold water provides:

• No UVB radiation

• No photochemical conversion mechanism

• No pathway to synthesize vitamin D

Cold exposure may affect vitamin D metabolism through various hormonal pathways, but it cannot produce vitamin D. That requires sunlight (or supplementation/dietary intake).

Why Single Studies Are Problematic in Wellness Marketing

Scientists become concerned when wellness businesses share single studies because:

1. The Bradford Hill Criteria for Causation

Establishing causation in biomedical science requires multiple lines of evidence:

• Consistency - findings replicated across multiple studies

• Strength - large effect sizes with appropriate statistical power

• Dose-response - clear relationship between exposure and outcome

• Plausibility - biologically reasonable mechanism

• Coherence - fits with existing knowledge

• Experiment - intervention studies support observational findings

A single underpowered rat study with methodological flaws meets none of these criteria.

2. The Replication Crisis

Many published studies fail to replicate. A 2015 study in Science found that only 39% of psychology studies could be replicated. In biomedical research, estimates suggest 50-89% of studies have design, methodological, or analytical issues that compromise their conclusions.

3. The "Telephone Game" Effect

What often happens:

1. Scientists publish: "Limited vitamin D supplementation effects in chronic shallow-water stress model"

2. Press release says: "Vitamin D may protect brain during cold exposure"

3. Blogger writes: "Cold water and vitamin D—the brain connection!"

4. Social media posts: "Cold plunge increases vitamin D!"

Each step moves further from what the research actually showed.

4. Cherry-Picking vs. Systematic Review

Evidence-based practice requires:

• Systematic reviews of multiple studies

• Meta-analyses when appropriate

• Assessment of study quality and bias

• Consideration of contradictory evidence

Single studies—especially those with significant limitations—should never be the basis for health claims.

What Evidence-Based Cold Water Immersion Research Actually Shows

Let's look at what the preponderance of evidence demonstrates about therapeutic cold water immersion (done properly—full body submersion, appropriate temperatures, controlled duration):

Inflammation and Recovery

Systematic review (Machado et al., 2016): Cold water immersion reduces delayed onset muscle soreness and perceived fatigue compared to passive recovery. European Journal of Applied Physiology

Meta-analysis (Leeder et al., 2012): Cold water immersion improves recovery of muscle power and reduces muscle soreness following exercise. British Journal of Sports Medicine

Metabolic Effects

Randomized controlled trial (Søberg et al., 2021): Regular winter swimming combined with other thermogenic activities increased brown adipose tissue activity and improved cold-induced thermogenesis and insulin sensitivity. Cell Reports Medicine

Research (van der Lans et al., 2013): Cold exposure activates brown adipose tissue and increases energy expenditure. Journal of Clinical Investigation

Mental Health and Mood

Case study (van Tulleken et al., 2018): Open water swimming showed significant symptom reduction in treatment-resistant major depressive disorder. BMJ Case Reports

Research (Shevchuk, 2008): Cold showers may have an antidepressant effect through increased beta-endorphin and noradrenaline levels. Medical Hypotheses

Cardiovascular and Immune Function

Research (Buijze et al., 2016): Regular cold showers resulted in 29% reduction in sickness absence from work. PLoS ONE

Systematic review (Mooventhan & Nivethitha, 2014): Cold water immersion shows beneficial effects on immune function, circulation, and the autonomic nervous system. North American Journal of Medical Sciences

Important Caveats

These benefits occur with:

• Proper protocols - controlled temperature (50-59°F/10-15°C typically), appropriate duration (1-15 minutes)

• Gradual adaptation - building tolerance over time

• Medical screening - contraindicated for certain cardiovascular conditions

• Informed consent - understanding risks and benefits

The Standards We Should Hold Ourselves To

As wellness professionals, we have both an opportunity and a responsibility:

Best Practices for Research Communication

1. Read the full study - not just the abstract, press release, or someone else's interpretation

2. Understand study design - recognize the difference between animal and human studies, observational vs. experimental, correlation vs. causation

3. Assess limitations - sample size, methodology, funding sources, conflicts of interest

4. Look for systematic reviews - prioritize meta-analyses and systematic reviews over single studies

5. Consult experts - work with scientists or healthcare professionals to interpret complex research

6. Be transparent - acknowledge limitations and uncertainties in the evidence

7. Avoid overstatement - "research suggests" and "may indicate" are more accurate than "proves" or "shows"

Questions to Ask Before Sharing Research

• Is this a single study or part of a body of evidence?

• What was actually measured in this study?

• Does the methodology match the claim being made?

• What are the limitations the authors acknowledged?

• Does this finding have biological plausibility?

• Are there contradictory studies?

• Am I qualified to interpret these findings?

Why This Matters

When wellness businesses misrepresent research:

• It harms clients: People make health decisions based on inaccurate information

• It undermines the industry: Scientists and medical professionals dismiss legitimate wellness modalities

• It invites regulation: Unsubstantiated health claims lead to increased scrutiny and restrictions

• It's unnecessary: Cold water immersion has substantial evidence-based benefits that don't need embellishment

The Path Forward

Cold water immersion doesn't increase vitamin D. It doesn't need to. The actual evidence shows compelling benefits for:

• Exercise recovery

• Metabolic health

• Mental wellbeing

• Immune function

• Circulation

These legitimate benefits are remarkable enough. We don't need to manufacture additional claims or misinterpret research to make our modalities valuable.

At Kairos, we're committed to evidence-based wellness. That means:

• Accurately representing scientific research

• Acknowledging what we know and what remains uncertain

• Prioritizing client safety and informed consent

• Partnering with healthcare providers

• Continuously updating our knowledge as new evidence emerges

For Wellness Professionals

If you're passionate about sharing research with your community:

• Consider taking courses in research literacy

• Partner with scientists or clinicians as advisors

• Use peer-reviewed systematic reviews rather than single studies

• Be humble about the limits of current evidence

• Focus on the substantial proven benefits of your modalities

The wellness industry will earn greater credibility—and serve clients better—when we commit to scientific rigor alongside our passion for holistic health.

Resources

For Research Literacy:

• Understanding Health Research (free online course from Yale)

• Critical Appraisal Skills Programme (CASP) checklists

• The Cochrane Collaboration's consumer resources

For Cold Water Immersion Evidence:

• PubMed searches for "cold water immersion" + "systematic review"

• Sports medicine and exercise physiology journals

• Consult with exercise physiologists or sports medicine physicians

Have questions about the research behind our services at Kairos? I'm always happy to discuss the evidence base and share scientific references. Let's build a wellness industry grounded in both compassion and scientific integrity.

Rebecca N. Harris, PhD in Physiology

Kairos Float & Wellness Studio

Where Science Meets Wellness

References

Buijze, G. A., Sierevelt, I. N., van der Heijden, B. C., Dijkgraaf, M. G., & Frings-Dresen, M. H. (2016). The effect of cold showering on health and work: a randomized controlled trial. PLoS ONE, 11(9), e0161749.

Korewo-Labelle, D., Karnia, M. J., Myślińska, D., & Kaczor, J. J. (2025). Impact of chronic cold water immersion and vitamin D3 supplementation on the hippocampal metabolism and oxidative stress in rats. Cells, 14(9), 641.

Leeder, J., Gissane, C., van Someren, K., Gregson, W., & Howatson, G. (2012). Cold water immersion and recovery from strenuous exercise: a meta-analysis. British Journal of Sports Medicine, 46(4), 233-240.

Machado, A. F., Ferreira, P. H., Micheletti, J. K., de Almeida, A. C., Lemes, Í. R., Vanderlei, F. M., ... & Pastre, C. M. (2016). Can water temperature and immersion time influence the effect of cold water immersion on muscle soreness? A systematic review and meta-analysis. Sports Medicine, 46(4), 503-514.

Mooventhan, A., & Nivethitha, L. (2014). Scientific evidence-based effects of hydrotherapy on various systems of the body. North American Journal of Medical Sciences, 6(5), 199.

Shevchuk, N. A. (2008). Adapted cold shower as a potential treatment for depression. Medical Hypotheses, 70(5), 995-1001.

Søberg, S.,Løfgren, J., Philipsen, F. E., Jensen, M., Hansen, A. E., Ahlman, E., ... & Sjödin, A. (2021). Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine, 2(10), 100408.

van der Lans, A. A., Hoeks, J., Brans, B., Vijgen, G. H., Visser, M. G., Vosselman, M. J., ... & van Marken Lichtenbelt, W. D. (2013). Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. Journal of Clinical Investigation, 123(8), 3395-3403.

van Tulleken, C., Tipton, M., Massey, H., & Harper, C. M. (2018). Open water swimming as a treatment for major depressive disorder. BMJ Case Reports, 2018, bcr2018225007.