Vitamin D plays an essential role in the quality of bone and muscle tissue, but not only that. However, 75% of French people have levels that are too low, so much so that taking vitamin D3 has almost become a reflex in autumn and winter. But what about from spring or summer? Here is the answer, in three key points.
Vitamin D is a moleculemolecule fat-soluble which brings together several substances, calciferolscalciferols. The two most common are vitamin D2 or ergocalciferol, produced by plants, and vitamin D3 or cholecalciferol, of animal origin and produced by the skin under the action of rays. ultravioletultraviolet B. It is considered a true hormone, due to its many physiological roles.
What is vitamin D used for?
Vitamin D3 is essential for calcium and phosphorus metabolism. It increases their absorption in the intestine and reduces their elimination in the urine, which allows normal blood levels to be maintained. THE calciumcalcium thus promotes the mineralization of tissues, particularly bones, cartilage and teeth, muscle contraction, nerve transmission and coagulation. Vitamin D is also involved in hormonal regulation, the activity of immune systemimmune systemand the differentiation of skin cells.
To cover daily vitamin D requirements, there are two ways: sunsun and food.
Tanning side, vitamin D is present in the body in the form of a precursor – a derivative of cholesterolcholesterol – then synthesized into active vitamin D3 at the level ofepidermisepidermis under the action of UVB rays. Exposure to solar radiation for 15 to 20 minutes per day should constitute a sufficient intake of vitamin D, provided that at least 35% of the body surface is exposed.
However, other factors come into play, such as time of day, latitudelatitude, age, gender, skin tone… And yes, the darker the skin, the less effective the synthesis of vitamin D is, so dark skin types will have to expose themselves for longer. The synthesis also decreases with the application of a sun protector which constitutes a barrier against UVB; However, this is not a reason not to protect yourself, as the effects of solar radiation on the skin are unfortunately not limited to vitamin synthesis but also, and increasingly, to burns and skin cancers (melanomasmelanomas).
On the plate side, a vitamin D2 intake comes from plants, like some cerealscereals, mushroomsmushrooms (chanterelleschanterellesporcini mushrooms, morels) and yeastsyeasts. Vitamin D3 comes from animals, in particular PiscesPisces fatty (sardines, mackerel, herring, salmonsalmon), their liverliver and the oils extracted from them, dairy products and egg yolk from animals supplemented with vitamin D. In France, the main foods contributing to vitamin D intake in the population are fish and dairy products, which contribute respectively to 19% and 25% of intakes in adults and 12 and 40% of vitamin D intakes in children.
Should you take food supplements?
The average intake in the French population through food is 3.1 micrograms per day in adults, or 5 times less than the recommended daily dose. Indeed, the Nutritional Reference for the Population (RNP) indicates 15 micrograms per day for adults in France, considering only the intake through food, and not the contribution of exposure to the sun.
However, vitamin D is not only found on the plate! Except in winterwinter or in certain regions, where solar exposure is very low, vitamin D intakes are supposed to be covered with daily exposure. In spring and summer, supplementation is therefore not necessary for an adult who monitors their food intake and is exposed – moderately but regularly – to lightlight of the sun.
If in doubt, ask your doctor to prescribe a dosagedosage blood to determine if supplementation is necessary and what dose to take. A deficiencydeficiency will manifest itself by muscle and bone disorders, to be monitored in particular in the elderly, infants, and pregnant and menopausal women, as well as in the case of certain restrictive diets.
