Cold Water and Hormesis — Part 1

Chapter 8: Cold Water and Hormesis

Cold water exposures improve immune responses. Ask any cold water swimmer or showerer and they will attest to having far fewer winter colds and chest infections and fewer illnesses overall. One study in which four groups of people were compared over many months supports these claims. The first group took hot-to-cold showers; the second did regular physical exercise; a third combined hot-to-cold showers and physical activity, whereas the fourth group did not change their behaviour. Compared to the fourth group, hot-to-cold showers resulted in a 29 per cent reduction in sick leave; physical activity resulted in a 35 per cent reduction in sick leave and the combination of physical exercise and routine cold showers resulted in a remarkable 54 per cent reduction in sick leave. The duration of the cold shower did not appear to make a difference. Participants reported an increase in energy levels, including many saying it was like the hit one gets from coffee. A further positive outcome was the improvement in quality of life, which was much higher in the cold water groups. Even though the vast majority reported a variable degree of discomfort during cold exposure, the fact that 91 per cent expressed the will to continue the routine after 90 days is perhaps the most indicative of any benefit. One of the big effects of cold water swimming is its impact on how many calories we burn when at rest. When we swim outdoors, the body must work hard simply to stay warm and consequently burn more calories. The colder the water, the harder the body works to convert fat to energy. When this is coupled with the exercise of swimming, the calorie burn is further increased. The same chemical and sympathetic nervous system changes for cold water showers apply to cold water swimming. So, when we swim in cold water, the extreme change in temperature increases the sympathetic nervous system activity and reduces blood flow to the skin, both of which result in harder pumping of blood around the body by the heart to body organs, prioritising important organs such as muscle, brain and kidneys. As a result, circulation is improved and toxins are more readily flushed out of our system. The ‘clean skin and healthy glow’ of regular cold water swimmers can be attributed to these physiological consequences. There is also good evidence to support associations between cold water swimming and decreases in tension, fatigue, improvement in mood and memory, and in general well-being. Sound evolutionary theories support the reasons why we find cold water exposure so invigorating. Humans’ lifestyle was mostly outdoors, with widely varying ambient temperatures, and frequent swimming or immersion in water of uncomfortable temperatures necessary to find food or escape predators.

Chapter 8: Cold Water and Hormesis

But, even though humans are homeotherms (our body maintains a constant core temperature of approximately 36.6°C), in modern life our utilisation of this sophisticated regulatory system is very low. And this is not a good thing as the system requires stimulation. The rapid disappearance of thermal stress from the lifestyle of humans in the last few thousand years, compared to its presence for millions of years in primates and hundreds of thousands of years in homo sapiens, has had a negative effect on human physical and mental health because the thermoregulatory system does not get enough ‘exercise’ or stimulation. Consequently, cold water exposure is hard-wired; it triggers this evolutionary response and is invigorating. The literature on the role of cold water in the treatment of depression is extensive and longstanding. The following case report from the British Medical Journal is a good illustration of how cold water swimming alleviated depression in a young female: ‘A 24-year-old woman with symptoms of major depressive disorder and anxiety had been treated for the condition since the age of 17. Symptoms were resistant to well-known antidepressant drugs. Following the birth of her daughter, she wanted to be medication-free and symptom-free. She commenced a programme of weekly open (cold) water swimming. This led to an immediate improvement in mood following each swim and a sustained and gradual reduction in symptoms of depression, and consequently a reduction in, and then cessation of, medication. On follow-up a year later, she remained medication-free.’ Depression and low mood are common with advancing years. This is mostly because of changes in life circumstances, such as loss of a partner or job, or intrinsic factors, such as age-related neurotransmitter changes. It is well recognised that the noradrenaline system does not function as it should in people who have depression. Cold water immersion regularises the system and thus helps with the symptoms of depression. This is so for young and old. Patients enquire about the safety of cold water exposure, particularly in relation to heart attacks. It is the case that people with known heart disease should not embark on sudden temperature changes without medical clearance. The sympathetic surge could induce a heart attack if vessels to the heart are already narrow because of atherosclerosis or clots. Otherwise, brief whole-body exposure to cold water (15–23°C) is safe and without significant side effects, either short-term or long-term. The effect on core body temperature is so negligible that hypothermia is hardly ever a concern unless exposed for excessive long periods to cold water.

Chapter 8: Cold Water and Hormesis

One further advantage of cold water exposure that is often overlooked but important to mention is the effect on skin. We talked about cold water causing a fresh, glowing look but it is also helpful for a well-known skin disorder that becomes more common with age – age-related pruritus, or itchy skin. With ageing, the skin struggles to retain oil and moisture and becomes dry. This results in itching and scaly red patches (the medical term for this is asteatotic eczema). Hot water showers and frequent hot water bathing aggravates or even causes asteatotic eczema. Cold water showers help to relieve the itching and do not cause dry skin to the same extent as hot showers. We can’t leave the topic of cold water without reference to the sea. Maps of the world’s population show that the bulk of humanity live near water. We live along coastlines, around the rims of bays, up the course of rivers and streams and on islands. We also vacation at the beach and find solace fishing on lakes. Nothing makes small children happier than the chance to splash through puddles. This human penchant for water makes evolutionary sense. When humans separated from apes and emerged from the forests of Africa, they stuck close to rivers and beaches, feasting on fish, clams and crabs. The marine diet was packed with omega-3 fatty acids – essential fatty acids that promote brain cell growth. Human brain growth began to increase exponentially thereafter.

Chapter 8: Cold Water and Hormesis

Living near blue spaces – i.e., in proximity to the sea – is linked to better mood, less depression, less anxiety and better overall well-being. This applies to all age groups and some studies suggest that it is particularly so as we get older. Remarkably, proximity to the sea can add four to seven years to lifespan. Most of the science on extended lifespan and the sea comes from the Blue Zones, all of which are on high terrain and by the sea but also have a number of other characteristics that influence longer, healthier life – for example, good diet, active communities, less pollution and good quality of drinking water. So, teasing out the independent contribution of living by the sea from all of these other factors is challenging. The fact that stress and depression are less common may also be contributory.