Back in the 1960s, U.S. Army researchers found that men who spent eight hours a day in a chamber at a temperature of 50° F (10° C) got used to the cold and stopped shivering after two weeks. Later studies conducted by Scandinavian and British teams also concluded that people can get used to a cool environment. And a recent review of studies confirmed that all people have the ability to acclimatize to cold.
For example, in one study a group of healthy men spent up to three hours a day sitting in baths of water at a temperature of 57°F (about 14°C).
At the start of the 20-day study, the participants shivered heavily, which is the human body's initial reaction to cold. Their heart rate and metabolism sped up, generating heat. At the same time, their blood vessels constricted and retreated from the surface of the skin, which led to a drop in skin temperature. In essence, the vascular system contracted, pulling blood toward the internal organs in an attempt to escape the external cold.
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But by the final day, much had changed. The shivering stopped. While the metabolism and heart rate still sped up in response to the cold-water bath, the blood vessels no longer constricted, and the skin temperature did not drop as it had before. The men reported less discomfort during the cold baths. At the same time, their blood samples contained fewer markers of cold stress and immune system activity. It seemed their bodies had gotten used to the cold.
«Everyone has the ability, to one degree or another, to acclimatize to cold», – says Marius Brazaitis, the first author of the study and a senior researcher at the Lithuanian Sports University. He is confident that the human body achieves acclimatization through a combination of various internal adaptations, which people can either encourage or suppress depending on their behavior.
There is evidence that a special type of fat tissue known as «brown fat» can help the body generate heat in response to consistently cold conditions. «Constant exposure to cold somehow activates brown fat, which, as we know, undergoes dramatic seasonal changes», – says Shingo Kajimura, a professor in the Department of Cell and Tissue Biology at the University of California, San Francisco.
Newborns have a lot of brown fat, which helps them stay warm, because they lack the muscle to shiver. Although people lose their reserves of brown fat as they grow up, studies have shown that the area around the upper part of the spine and neck either retains brown fat or produces new brown fat in response to cold.
The location of this fat is important. Kajimura says that the perception of temperature is controlled by the brain, which partly detects cold by registering the temperature of the blood entering it through the neck. «That's why, when you put on a scarf, you warm up», – he says. By warming the neck and the blood flowing through it, the scarf «tricks» the brain into believing it is warm – just as a cold cloth on the neck helps the brain cool down in summer. It is quite possible that, in response to regular exposure to cold, the brown fat in the neck area forms and becomes more active, thanks to which we feel more comfortable at lower temperatures».
Brazaitis believes that the human body possesses a number of different mechanisms that help it adapt to cold. But most people in the developed world suppress these adaptive mechanisms, protecting their bodies from «heat stress».
«Putting on more clothes, drinking more hot beverages, raising the temperature indoors, consuming more food, which increases the rate of internal metabolism – such behaviors prevent the body from becoming more resistant to cold», – he says.
According to Brazaitis, setting your home temperature a few degrees lower, dressing more lightly and spending more time outside in cold conditions will help your body acclimatize to the cold.
The fastest way to adapt to cold
«If you really want to speed up your body's acclimation to cold, a cold shower makes the body adapt quite quickly», – says John Castellani, a research physiologist from the United States. He suggests starting with a quick cold shower – say, 15 seconds – and adding 10 seconds each day.
Why we feel colder in damp weather: a doctor explains Spending time under a cold shower or in other cold conditions is safe for most people and may even bring some health benefits. But people at risk of cardiovascular disease should be careful.
«The first thing that happens when you are exposed to cold is the constriction of blood vessels and a rise in blood pressure», – says Castellani.
Thus, exposure to cold, especially severe cold, can trigger a heart attack or other problems in people with heart conditions. But if your heart is healthy and you want to use the body's natural ability to adapt to cold, a week of cold showers in the morning should help.
