From 5 to 10 centimeters of snow expected in the plain, department on orange alert “snow and ice”, temperatures around 0°C: the cold is well back. And it could turn out to be harmful for some people, such as those who have a fragile heart because at these very low temperatures, the latter must redouble its efforts to function well. But it’s good news for others, especially those who suffer from sleep disorders or joint pain. We tell you why.
Cold is bad for immunity
It is not a received idea to think that the cold decreases the immune response. Because the blood concentrates on the vital organs, which prevents the cells responsible for immunity, such as white blood cells and polynuclear cells, from circulating well throughout our body. Result: we become much more sensitive to minor sores… and to the many viruses that are circulating this winter (flu, bronchiolitis, Covid-19).
The cold is less good for fragile hearts
When winter arrives, our heart prepares to defend itself against the cold, but the fight will not be on equal terms for people with hypertension or a history of heart attack. Because “the body must mobilize more energy to maintain body temperature, i.e. the heart will beat faster, its oxygen consumption will increase, the vessels will contract, which will promote coagulation some blood“, notes Dr. Patrick Assyag, vice-president of the French Federation of Cardiology.
“In winter, the slightest physical activity requires a major effort on the heart, so that walking in the cold is equivalent to running a 100 meters. And smokers are more at risk, because tobacco intensifies the narrowing of coronary arteries.Finally, the cold is a source of dehydration, which reduces the fluidity of the blood and also requires more effort from the heart.
What are the benefits of cold for the body?
Body temperature must drop to ensure restful sleep. “She is not on a plateau at 37°C all the time, there is a minimum which is between 4 and 6 am“, specifies Dr. Sylvie Royant-Parola, author of How to get back to sleep on your own (ed. Odile Jacob). That of the bedroom is therefore important. The ideal temperature for good sleep: between 16 and 18°. Open the bedroom window a few minutes before going to bed, let the cold air in before slipping under the duvet and you will find sleep more easily.
With the cold comes brown fat or, to put it more elegantly, brown adipose tissue, which burns calories faster than white fat. It is very present in hibernating mammals, to help them maintain a good body temperature: this is called thermogenesis. Infants also have them, which allows them to maintain their temperature at 37°C. However, it turns out that a certain percentage of these brown fats is still present in adults, especially in women. “This is interesting in winter, because the two fats do not melt in the same way. For the white, it’s sport, and for the other, it’s the cold“, explains Dr Frédéric Saldmann, cardiologist and nutritionist.
