Cold-water swimming
Humans are versatile mammals with adaptive capabilities to withstand a diverse range of conditions in their environment, such as exposure to extreme hot or cold climates. Since ancient times, cultures all around the world have exposed the body to cold temperatures as a form of health intervention.
In recent times the health effects of cold-water swimming on the body have received attention through a number of scientific studies. The results suggest that while cold-water swimming initially triggers the “cold shock response”, characterized by a gasp reflex, rapid breathing, and increased heart rate and blood pressure, regular immersion in cold water leads to acclimation in the body, resulting in some important health benefits.
Recent studies on cold water immersion and swimming:
A number of studies have investigated the physiological responses of cold-water exposure in the body.
- Canadian study 2025:
Researchers from the University of Ottawa in Canada recruited 10 healthy young males as participants to take a daily 1-hour long cold-water dip over 7 days in their laboratory. Regular blood samples were used to measure how their bodies were responding at a cellular level, to test the hypothesis that cold water acclamation may mediate key cellular protective mechanisms, such as autophagy (the body’s cellular recycling system of reusing old and damaged cell parts) and the cold-shock response. The thinking was that regular exposure may improve the body’s fundamental reaction to environmental stress, using chilly temperatures in this case.
The study’s observations indicate that repeated cold exposure may enhance cellular tolerance to the cold, after a minimum of 4 days, as witnessed through improvements in autophagic activity and the cold shock response, due to acclimation. After initially spiking, signs of apoptosis (programmed cell death) and inflammation reduced over the week.
The researchers concluded that cold exposure may be a viable approach to improve autophagic function through non-pharmacological interventions, leading to potential improvements in human health. Autophagy is a critical cellular protective mechanism, particularly as we age.
Limitations of the study include the fact that only 10 healthy young men participated, and in a laboratory environment. The study probably needs to be extended to bigger groups of participants, including women and various age groups, to see if the findings apply generally.
- Irish study 2023:
Cold water swimming is a popular activity with a particularly strong following along the west coast of Ireland. The Primary Care Trials Network Ireland collected data by conducting interviews on a sample of cold-water swimmers, recruited by an online survey. Participants were selected in order to ensure a good distribution of age, gender, and swimming frequency. A total of 10 participants were selected and extensively interviewed, following a semi-structured approach. Participants were interviewed according to pre-determined questions but asked to elaborate on their responses. Their ages ranged from 22 to 75 and they swam all year round.
The results yielded three main themes, namely mental health and well-being, physical impact, and community engagement, with several sub-themes.
- Mental health: All the participants indicated that cold water swimming had a positive effect on their mental health, including general mood and offsetting the winter seasonal blues.
- Energy: Participants felt more energetic and fuller of life after a swimming session. It also yielded more energy and enthusiasm to engage in other forms of physical activity.
- Escapism: They shared that the act of cold-water swimming functions as a reset button for the day and a reliever of stress in stressful lives and occupations.
- Community engagement: The majority (8/10) of participants engaged in cold-water swimming in a group setting, with a strong sense of togetherness developing as well as a high regard for safety, as most of them felt it was unsafe to go swimming on their own.
- Strengthening ties to locality: Participants found the cold-water swimming community is an inclusive and safe way to build ties to their local area, while appreciating nature and the sea.
- Physical health: Participants found that their physical health had improved since starting cold-water swimming. Apart from relief from back pain for one individual, some participants noted a reduction in blood pressure and improved cholesterol markers.
- Immune system effects: Participants experienced a reduced incidence of upper respiratory tract infections, such as colds and coughs.
All participants found that cold-water swimming lifted their mood and made them feel generally good about themselves. The effects they experienced appeared to be more significant than from any other activities they undertook.
- Other studies:
A 2022 multiple database survey on published literature tried to determine whether voluntary exposure to cold water has health effects on humans, examining 104 studies with relevance to the topic.
The survey found that while many of the studies demonstrated significant effects of cold-water emersion on various physiological and biochemical criteria, it was difficult to determine conclusively whether cold-water emersion is beneficial for health. Some studies involved passive cold-water emersion, while others involved active cold-water emersion. Clear conclusions from most of the studies were hampered as the studies were carried out in small groups, often of one gender, and differed in exposure temperature and salt composition.
The survey found that there is increasing scientific support that voluntary exposure to cold water may have a number of health benefits. Several areas were identified that need further investigation in new controlled research studies, such as the effect on the immune system, (for example, tolerance to stress and respiratory infections), potential effects on the cardiovascular system, improved insulin sensitivity, and improved mental health are all areas with promising results and warrant further investigation.
The study concluded:
“Until we have more concrete scientific evidence, the topic will continue to be a subject of debate.”
Conclusion:
In spite of the limitations of current small and non-standardized studies, findings suggest that once participants in regular cold-water swimming have gone through a short period of acclimation, they experience improvements in mental and physical health.
References:
The effect of 7-day cold water acclimation on autophagic and apoptotic responses in young males. Published February 2025 in Advanced Biology, Volume 9, issue 2. (www.advanced.onlinelibrary.wiley.com)
A week of swimming in old water can change you on a cellular level. Published 6 April 2025. ScienceAlert. (www.sciencealert.com)
Cold water swimming and its potential health benefits: a qualitative study of participants’ views and experiences. Published October 2023 in the Irish Medical Journal. Vol 116. (www.imj.ie)
Health effects of voluntary exposure to cold water – a continuing subject of debate. Published September 2022 in the International Journal of Circumpolar Health. Taylor & Francis Online. (www.tandfonline.com)
HEALTH INSIGHT.