Vitamin D, vitamin star

Much has been made of the “D” for its supposed virtues on immunity during the Covid-19 pandemic. Especially since a majority of French people do not consume enough.

The “D” is a special case. Here is a vitamin present in certain foods, and produced by the exposure of the body to the sun, whose needs cannot be covered. We are all in deficit, underlines the National Food Safety Agency in a recent report. According to her, the average intake in French adults is 2.8 micrograms / day, while the recommendation is 15 micrograms daily. Why such a discrepancy?

First, because our type of food is low in vitamin D. It must be said that this nutrient is not so common in food. It is found mainly in fish oils, to a lesser extent in butter and eggs – very little in vegetables. The other source of vitamin D is exposure to the sun, under the action of ultraviolet radiation (UVB). But again, this is not enough.

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Our way of life does not favor this synthesisexplains Dr Laurent Chevallier, nutritionist at Montpellier University Hospital. In our latitudes the effect of UV rays is only effective between March and October. In addition, we have become sedentary: we spend 75 to 90% of our time indoors. »

All deficient, but not necessarily deficient

Today, more than 70% of French people fail to meet the average nutritional requirements for vitamin D. In other words, almost all of us are deficient. But fortunately not all deficient, that is to say with a deficiency large enough to experience a proven impact on health. However, this critical situation concerns 7% of adults, 4% of children and 13% of adolescents. They suffer, for the most part, from a deficiency in blood calcium whose maintenance depends largely on vitamin D. This can cause muscle and bone disorders: loss of tone, tetany attack, convulsions, soft bone syndrome, rickets in young people. As for bone mass, it may be reduced in the elderly, thus increasing osteoporosis and the risk of fracture.

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How to avoid these dangers? First of all, balance your diet by forcing on foods rich in vitamin D – at the same time, avoid a sedentary lifestyle and move outdoors as soon as possible. “ For food, you must first bet on oily fish, herring, salmon, sardines, mackerel, says Dr. Laurent Chevallier. You should eat it at least once a week. Then come eggs, whole dairy products, but without overdoing it. Plus, of course, promote exposure to the sun whenever possible”.

Supplements on medical advice

Should we, in addition, supplement? The question divides the expert community. The orthodoxy in this area recommends limiting supplements to specific situations: growing infants and young people, the elderly who have difficulty eating properly, pregnant women, systematically at 7e months and, often, postmenopausal women in whom hormonal changes tend to cause significant bone demineralization. Special diets with the exclusion of fish and certain diseases that interfere with intestinal absorption can also be indications.

“But, in any case, this supplementation must be done under medical supervision.says Dr. Chevallier. The health professional will carry out a dietary survey to possibly optimize your intake, then, using a blood test, he will assess the extent of the deficit and the need to supplement. You have to be careful because excess vitamin D can be harmful. By raising blood calcium levels, they sometimes lead to calcification of certain organs. Ideally, the dosage of vitamin D should be coupled with that of parathyroid hormone (PTH), which is involved in the regulation of calcium, in order to properly interpret the results. »

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Other experts go further: they campaign for an extension of the prescription of vitamin D. Their argument is simple: the deficiency in “D” is a real epidemic, while, every day, we discover new virtues to this vitamin. . It is known to be involved in hormonal regulation and immunity. Moreover, many epidemiological studies carried out comparing populations with high and low vitamin D status have given encouraging results: there is less diabetes, less cardiovascular disease, and even less cancer in populations having high blood levels of vitamin D. More studies are needed, but, for sure, we are not done talking about vitamin D.

An anti-Covid vitamin?

During the Covid-19 pandemic, some doctors saw vitamin D as an effective antiviral weapon. However, the studies carried out have not proved conclusive. What exactly did the researchers find? That there would be a correlation between vitamin D deficiency and the severity of the disease. It is known that the coronavirus stimulates the renin-angiotensin hormonal system, which can cause many pathologies. Vitamin D would counterbalance this deleterious effect by slowing down this system, and could thus block the evolution towards a severe form. But this is only a hypothesis that remains to be demonstrated. Caution is required and health institutions believe that the scientific data remain insufficient to decide on the effectiveness of vitamin D against Covid. Accordingly, routine supplementation is therefore not recommended to prevent or treat infection.


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