Should you take vitamin D in autumn-winter?

Vitamin D is an important vitamin for the body. It is essential for bone mineralization and is also involved in immunity. Vitamin D behaves like a hormone, which explains why it has an overall action on health. It is both anti-infectious, anti-inflammatory… It is also involved in controlling blood pressure.

Vitamin D is produced by the skin under the action of UV rays Most of our vitamin D intake – over 80% – comes from the sun. Sun exposure is therefore very important to cover our needs.

In our latitudes, you can fill up on vitamin D by exposing your forearms, face and neck for about a quarter of an hour, without sunscreen, from April to October, but it’s much more complicated in autumn and winter, with the lack of sunshine and especially UVB.

It is estimated that around 40% of the population lack vitamin D, that is to say, have a blood level of less than 20 nanograms per millilitre, especially at the end of winter. 6% would be in real deficiency.

Foods richest in vitamin D

Vitamin D is also found in food, in oily fish, dairy products, in egg yolk, certain mushrooms… But food alone only regulates a very small part of the problem. Its contributions are limited and constitute only 10 to 20% of our needs. There is cod liver oil, which contains a lot of vitamin D. Our ancestors used to give it to children to prevent rickets. But its taste is not appreciated by all.

All this explains why supplementation is often prescribed in winter, in the absence of official recommendations. This is even more true for the elderly because, even if they are exposed to the sun, they synthesize vitamin D less well. at the level of the skin”, explained to me Pr Cédric Annweiler, geriatrician at the CHU of Angers.

Who needs to supplement?

In a recent opinion, the Haut Conseil de la santé publique does not recommend vitamin D supplementation for the general adult population. He believes that there are no solid scientific studies confirming its benefit in healthy people.
Admittedly, studies have shown that a vitamin D deficiency is correlated with a greater risk of infections, cancers, and cardiovascular problems. But beware of the shortcut, correlation does not mean causation, and at this stage, nothing serious has yet been demonstrated on the supposedly protective role of vitamin D supplementation against the occurrence of these diseases.

In addition, we cannot say that supplementation is completely risk-free.. It is therefore not advisable to take vitamin D in self-medication. Agathe Billette de Villemeur, public health physician and epidemiologist points out that “today the benefits of supplementation are only proven in cases of osteomalacia – when you have soft bones – associated with a real deficiency, i.e. a blood level of less than 10 nanograms per milliliter.

For people particularly at risk of vitamin D deficiency, such as the elderly living in institutions, obese people or people with very pigmented skin… the question of supplementation can be asked on a case-by-case basis with your doctor.. However, the scientific data are not sufficient to recommend systematic supplementation.

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