A cold dip can feel invigorating, especially when shared with friends. That experience matters, but it is not the same as evidence of stronger immunity or a longer life. Cold-water immersion places real demands on breathing and circulation. Its health claims and safety deserve equal attention.
The newer review found a mixed picture
Cain and colleagues' 2025 systematic review included eleven studies involving healthy adults. It reported some time-dependent changes in stress and other outcomes, but results were not consistently beneficial across measurements. Immediate inflammation increased in pooled analyses, and immediate immune-function benefits were not established. A brief physiological change is not a diagnosis or a proven long-term advantage.
Studies used different temperatures, durations and methods, with limited diversity and relatively few trials. They did not establish that cold immersion prevents illness, treats depression or extends lifespan. Controlled baths and showers also cannot capture all the risks of open water, currents and weather.
The sea is not a treatment room
RNLI guidance warns against jumping straight in and advises gradual acclimatisation, a buddy and appropriate preparation. Cold-water shock can cause gasping and breathing difficulty. People with heart disease or other relevant conditions should seek medical advice before cold immersion. Avoid breath-holding challenges in water, and do not treat a social-media exposure time as a safe prescription.
- Never swim alone.
- Check conditions and a safe exit.
- Acclimatise gradually rather than jumping in.
- Have a warming plan and stop before becoming unwell.
There is no requirement to cold plunge to use Zhen's healthy-ageing approach. If the aim is better fitness, manageable activity has a firmer evidence base. An enjoyable dip can be a personal choice, but a wellness plan should not turn an optional and potentially risky activity into an obligation.
Putting this into practice at Zhen
At Zhen Wellness in Onchan, Isle of Man, we help you turn health information into realistic next steps. The £97 Longevity MOT is a standalone 60-minute assessment of your history, priorities, posture, mobility and body composition estimates, with pain mapping where relevant. It is not a biological-age blood test, medical diagnosis or prediction of lifespan. Any further service is chosen separately around your needs, with costs discussed before you decide.
Research and safety
Sources checked on 14 October 2026. Studies describe their own participants and interventions, not Zhen treatment outcomes. Evidence can change; research is not free of bias. This article is general education, not individual medical advice. Adult fasting or exercise protocols are not suitable instructions for children. Seek appropriate clinical advice for new symptoms, medical conditions, pregnancy or treatment changes. Never stop prescribed medicines to follow a wellness plan.