Health Effects of Voluntary Cold-Water Exposure

Date: 2022 
Authors: Didrik Espeland, Louis de Weerd, James B. Mercer
Published in: International Journal of Circumpolar Health

Executive Summary

This review article examines the health effects of voluntary cold-water immersion (CWI) by analyzing 104 relevant studies. The findings suggest that CWI may influence physiological and biochemical functions, including metabolism, immune response, cardiovascular health, and mental well-being. However, the results are mixed due to variations in study conditions, participant experience, and water temperature. While some benefits—such as improved insulin sensitivity, fat reduction, and stress resilience—are observed, more rigorous research is needed to draw firm conclusions.

Key Findings

Physiological and Metabolic Effects

• CWI activates brown adipose tissue (BAT), which may aid in fat metabolism and energy regulation. BAT activation helps maintain body temperature in cold environments by burning calories to generate heat. Studies suggest that this metabolic process may contribute to improved energy balance and reduced fat accumulation (pg. 4, para. 3).
• It may enhance insulin sensitivity, reducing the risk of type 2 diabetes and metabolic diseases. Repeated cold exposure has been linked to decreased insulin concentrations and improved glucose metabolism, potentially offering a non-pharmacological method for managing insulin resistance (pg. 9, para. 2).
• Some studies indicate a shift in fat metabolism, possibly supporting weight regulation and energy expenditure. Cold exposure appears to increase lipid oxidation, meaning the body may rely more on fat stores for energy, which could be beneficial for individuals seeking weight loss (pg. 7, para. 5).

Cardiovascular Effects

• CWI elevates heart rate and blood pressure, which may strain the cardiovascular system, especially in non-acclimated individuals. The body's initial response to cold shock includes a spike in blood pressure and heart rate, which could pose risks for those with pre-existing cardiovascular conditions (pg. 6, para. 6).
• Long-term exposure may reduce cardiovascular risk factors, such as cholesterol levels and oxidative stress markers. Cold-adapted individuals have shown lower levels of harmful cholesterol and improved antioxidant enzyme activity, which may contribute to heart health (pg. 6, para. 3).
• Cold shock responses may increase the risk of arrhythmias, particularly in individuals with heart conditions.The conflicting autonomic nervous system responses triggered by cold immersion may disrupt heart rhythm, potentially leading to dangerous irregular heartbeats (pg. 7, para. 2).

Immune System and Inflammation

• CWI increases levels of immune cells (T lymphocytes, IL-6, and monocytes), potentially improving immune resilience. Some studies have observed an increase in immune cell activity and anti-inflammatory cytokines, which may help the body respond more effectively to infections (pg. 10, para. 3).
• It may reduce oxidative stress, leading to an adaptive stress response and improved tolerance to environmental stressors. Regular exposure to cold water has been linked to increased antioxidant enzyme activity, which may help neutralize free radicals and reduce cellular damage (pg. 10, para. 6).
• No significant difference in upper respiratory infections (URTIs) was found between cold-water and pool swimmers. Despite anecdotal claims that cold-water exposure strengthens immunity, a comparative study found no notable differences in the frequency of colds or flu between the two groups (pg. 10, para. 8).

Mental Health and Psychological Effects

• Cold exposure stimulates noradrenaline and endorphin release, which may have antidepressant effects. The strong neural stimulation from cold water may enhance mood and provide relief from depressive symptoms by increasing neurotransmitter activity (pg. 11, para. 3).
• Some studies suggest mood improvements and reductions in stress, fatigue, and tension among winter swimmers. Regular participants in cold-water immersion report feeling more alert, energized, and mentally resilient after their swims (pg. 11, para. 5).
• A case study found CWI beneficial in alleviating symptoms of postpartum depression. A woman who engaged in regular cold-water swimming was able to discontinue her antidepressant medication and maintain improved mental health (pg. 11, para. 4).

Exercise Recovery and Physical Performance

• CWI is often used as a post-exercise recovery tool to reduce muscle soreness and inflammation. Studies on athletes show that immersion in cold water after intense exercise can help speed up recovery and reduce muscle pain (pg. 11, para. 8).
• Athletes using cold-water recovery show faster sprint performance recovery and lower muscle damage markers. Cold exposure appears to decrease muscle damage indicators like creatine kinase (CK), which is commonly elevated after strenuous activity (pg. 11, para. 9).

Potential Risks and Negative Effects

• Cold shock response can cause gasping, hyperventilation, and loss of consciousness, increasing the risk of drowning. The initial physiological reaction to sudden immersion in cold water can lead to an involuntary inhalation of water, which is a primary cause of drowning (pg. 6, para. 7).
• Long-term effects on cardiac health remain uncertain, as some studies suggest increased cardiac stress. While adaptation to cold may lower some cardiovascular risks, the repetitive stress on the heart could be problematic for certain individuals (pg. 7, para. 5).
• Hypothermia and frostbite are significant risks, particularly for prolonged exposure or in extreme temperatures. Without proper acclimatization or protective measures, extended exposure to cold water can lead to dangerous drops in body temperature and tissue damage (pg. 12, para. 2).

Source: Health effects of voluntary exposure to cold water – a continuing subject of debate