How to fill up on Vitamin D and avoid deficiencies

Essential for the good health of our bones and muscles, this vitamin is mainly provided by the sun. But diet also plays a big role. Here is the recipe to ensure an optimal intake.

Save who can, winter is here. The sun is lacking and, with it, vitamin D. In fact, it is essentially synthesized by the body thanks to the exposure of our epidermis to ultraviolet rays (UVB). This fat-soluble vitamin, which is fixed in fat, comes from 30% from food and 70% from sun exposure. And this, on the condition of offering for 20 minutes a day the equivalent of 30% of the surface of the body to zenithal rays, without filtering sunscreen or atmospheric pollution, which blocks ultraviolet rays.

In our latitudes, between October and April, we produce very little vitamin D. As a result, "80% of French people have a deficit," says Dr. Jean-Michel Lecerf, head of the nutrition department at the Institut Pasteur de Lille. . Certain categories of the population are even more likely than others to be deficient, such as people with dull or dark pigmentation, as well as elderly subjects whose skin synthesis is less efficient. This is why they are advised to go out regularly and take advantage of the slightest sunshine, taking care to uncover their forearms, hands, and face.

A protective role

Vitamin D plays an essential role in the mineralization and maintenance of bone capital, by promoting the intestinal absorption of calcium. "It is a protective factor against rickets, one of the major growth disorders in children, against osteomalacia, or soft bone disease, generally coupled with bone pain, muscle weakness, and fatigue, especially in young women with multiple and close pregnancies, and against senile osteoporosis, which increases the risk of fractures", indicates Marie-Christine Boutron-Ruault, doctor and director at the National Institute of Health and medical research (Inserm).

Is this its only function? Several epidemiological studies have highlighted that vitamin D deficiencies are associated with an increased risk of breast, colon, and prostate cancers, cardiovascular diseases, neurodegenerative pathologies, or even macular degeneration linked to age (AMD). "If this vitamin is, in fact, a hormone and that vitamin D receptors are present in a very large number of cells in the body, interventional studies are nevertheless struggling to provide definitive proof", notes Dr. Jean -Michel Lecerf.

A new track could however emerge: the potential effect of vitamin D, highlighted in the current epidemic context, in particular during the first wave of Covid-19 which was accompanied by strict confinement. “The first observational studies showed that more than 80% of severe forms of Covid-19 affected patients who were deficient in vitamin D (1)”, summarizes Dr. Boutron-Ruault. More than fifty international clinical studies are underway to assess the effectiveness of vitamin D in the treatment and prevention of SARS-CoV-2 infection. In the immediate future, and this was the meaning of the notice published on April 17, 2020, by the National Health Security Agency (Anses) which invited the French to “ensure an adequate intake of vitamin D through food”, do not neglect to consume it. This contribution weighs for less than a third, but it counts, especially in periods when the UV index is close to zero.

Prioritize fortified dairy products

“There are two kinds of dietary vitamin D: vitamin D2 (ergocalciferol) which is of plant origin, and vitamin D3 (cholecalciferol) which is found in animal products. Both are useful, but vitamin D3, which is also the one synthesized during sun exposure, is a bit superior because it contributes to more effectively increasing the blood level of 25-hydroxyvitamin D (25-OHD), a form under which vitamin D is stored in the body,” explains Dr. Lecerf. “The main sources, for both adults and children, are dairy products, especially those enriched with vitamin D, says Gwenn Vo Van-Regnault, Nutrivigilance project manager at ANSES. Then comes fatty fish, limited to one serving per week, then offal, especially the liver, egg yolk, fat, or even certain mushrooms, the only vegetables to contain it.