By Dr Yakira Mishan

As someone who detests cold water, it feels like not a day goes by without someone telling me how a cold water immersion (CWI) will do everything from manage my stress to aid in muscle recovery and of course, prevent aging. So while the idea of ice-cold water truly makes me want to run in the opposite direction I felt that these claims warranted a scientific dig into the literature.

There are many claims in the popular media that CWI can boost the immune system, treat depression and burn calories. A few studies have provided scientific evidence that CWI may be effective in the treatment of chronic autoimmune inflammation, increase brown adipose tissue activation and therefore decrease cholesterol levels, and have a positive effect on stress regulation. The issue with many of these other claims is that there are many confounders – those who are more likely to engage in CWI are also more likely to exercise, eat healthily and even meditate.1

Cold water immersion offers a physiological challenge to the body and in response to this cold exposure our bodies must activate shivering for thermogenesis, non-shivering thermogenesis through activation of brown adipose tissue, cutaneous vasoconstriction followed by cold-induced vasodilation and finally a cardiopulmonary response of cold shock – increased blood pressure, tachycardia and hyperventilation. This is balanced by the dive reflex (sinus bradycardia, peripheral vasoconstriction and breath holding) .1,2

With regular CWI and exposure, there is evidence that we gain cold adaptation and with this, we have an improvement in cardiovascular risk factors such as a reduced ApoB/ApoA1 ratio and decreased oxidative stress markers. It is hypothesised that people who regularly engage in cold water swimming have increased non-shivering thermogenesis (brown adipose tissue) potentially mediated by an increase in the release of noradrenaline during CWI.1,3 This transformation in adipose tissue could be protective against diabetes and cardiovascular health.1

CWI may improve depressive symptoms for some through the increase in plasma noradrenaline, beta-endorphins and synaptic release of noradrenaline in the brain. However, these are mainly anecdotal reports on mood symptoms that have been reported rather than randomised control trials.1,4

Its effects on the immune system are still unclear. One study found that after 6 weeks of continuous CWI there was an increase in IL-6, which activates the production of acute phase reactants like CRP, and the total number of T lymphocytes including CD4, CD8 and Tregs. There was also an increase in granulocytes and lymphocytes in the bloodstream following CWI most likely due to an increase in noradrenaline. This may result in a boost in immune functioning but there really is no clear research supporting this idea.  Unfortunately, no research has examined anti-inflammatory cytokines such as IL-10 after CWI. This is in contrast with continuous cold exposure, which one study found may decrease immune functioning and predispose to infections. 1,5

According to some studies CWI following exercise in competitive athletes has been found to decrease creatinine kinase levels, most likely from decreased muscle blood flow, and improve recovery time of sprint speed 24 hours post-exercise.2 Another study in The Journal of Physiology found that CWI showed no decrease in the post-exercise inflammatory cellular stress response when compared to an active recovery protocol. The authors suggest that CWI may be beneficial in athletes within competition settings requiring fast turnaround times but that it may not actually be beneficial during pre-season training when muscle hypertrophy is the aim.6

CWI is not without risks, especially in the elderly or those with known comorbidities, and include arrythmias, increased blood pressure-related myocardial infarcts or cerebrovascular accidents and hypothermia or cold injuries. The reflex hyperventilation caused by cold immersion can result in confusion and disorientation, so if you are swimming in open water, ensure you are not alone.1,4

In summary – there is more research to be done. Furthermore, a standardisation in the protocols is needed so that research can truly be compared and implemented for the average person.

The very clear pro is that it helps you cool down quickly after a very sweaty exercise session. After prolonged periods of cold water immersion and swimming there does seem to be an increase in brown adipose tissue which increases non-shivering thermogenesis and basal metabolic rate. This may improve insulin sensitivity and cardiovascular risk but at present there is no evidence that it results in weight loss. It also may decrease muscle pain after strenuous exercise and assist with recovery turnaround times. It also may improve your mood by increasing catecholamines and endorphin release.

While there are some benefits to CWI at present, they do seem to be more anecdotal than proven in the scientific literature, especially as many of the published findings are anecdotal or findings from young and healthy athletes with many confounders to overall health.

I may give this a miss however, if you want to give this trend a try the most important thing is to remember to have it cleared with your GP first as there are real dangers, including death, that can be experienced with CWI in certain individuals.


  1. Esperland D, de Weerd L, Mercer JB. Health effects of voluntary exposure to cold water – a continuing subject of debate. Int J Circumpolar Health. 2022;81(1):2111789. doi:10.1080/22423982.2022.2111789
  2. Ihsan M, Watson G, Abbiss CR. What are the physiological mechanisms for post-exercise cold water immersion in the recovery from prolonged endurance and intermittent exercise? Sports Med. 2016;46(8):1095-1109. doi:10.1007/s40279-016-0483-3
  3. Scott M, Fuller S. The effects of intermittent cold exposure on adipose tissue. Int J Mol Sci. 2023,25(1):46. doi:10.3390/ijms25010046
  4. Minnins g, Stranbourough R. What to know about cold water therapy. Healthline:
  5. Jansky L,Pospisilova D,Honzova S, Ulicny B et al. Immune system of cold-exposed and cold-adapted humans. Eur J appl Physiol Occup Physiol. 1996;72(5-6):445-50. doi:10.1007/BF00242274
  6. Allan R, Mawhinney C. Is the ice bath finally melting? Cold water immersion is no greater than active recovery upon local and systemic inflammatory cellular stress in humans. J Physiol. 2017;595(6):1857-1858. doi:10.1113/JP273796