A new study on the link between vitamin D and reduced risk of respiratory infections, the largest ever conducted, confirms the beneficial effect of this vitamin in this area. A result that may be important for health services, even if supplementation would only be recommended for certain types of people.

Vitamin, D, would, have, a, beneficial, effect, against, respiratory, infections, for, people, at, risk

Unlike other vitamins that are mainly found in food, vitamin D is only found in a limited way in our plate (fatty fish, eggs, dairy products...). It is mainly acquired through exposure to the sun: UVB rays induce its synthesis, particularly in spring and summer. Maintaining a varied diet rich in vitamin D is therefore necessary to avoid any deficiency, because its role in good bone and musculoskeletal health is essential. In addition, many studies conducted before the coronavirus epidemic have shown a preventive effect on acute respiratory infections.

The question of whether vitamin D supplementation can reduce the risk of respiratory infections (pneumonia, influenza...) is therefore frequently debated. In a recent study published in the Lancet Diabetes & Endocrinology, a team of researchers from Karolinska Institutet (Sweden), Harvard Medical School and Queen Mary University of London, reviewed this topic in a large meta-analysis. Their results, based on 43 studies conducted on a total of 49,000 participants (not covering the question of whether vitamin D can protect against COVID-19) also provide insight into what the most effective daily dose would be.

 Daily or monthly supplementation?

The latter reveal that "the total protective effect against respiratory infections was 8%", but found, "that a daily dose of vitamin D has a much better effect than a dose administered weekly or monthly. "Provided, however, that the dose recommended by health professionals is not exceeded: there would be no need to exceed 400-1000 IU / day to obtain the best effect against respiratory infections. "The group receiving such a dose showed a 42% reduction in the risk of infection. ", the researchers add. But according to their recommendations, such supplementation would be required only for certain groups of people.

One conclusion is that health care professionals should pay attention to groups with a known risk of vitamin D deficiency, such as dark-skinned, overweight and elderly people," says the scientific team. "A daily dose of vitamin D can be very effective in reducing the risk of vitamin D deficiency," says the scientific team. "A daily dose of vitamin D may protect the skeleton and perhaps also reduce the risk of respiratory infections in these vulnerable groups. "But their findings emphasize that the general public is unlikely to benefit as much from such supplementation, knowing that it is never harmless as any other supplementation. "Vitamin D does not make healthy people healthier. ", concludes the scientific team. 

Note that these recommendations are similar to those of the Anses, which specifies that for certain populations such as newborns and infants, an additional intake of vitamin D is necessary to ensure a satisfactory status. As the body's ability to absorb or synthesize vitamin D decreases with age, the elderly are also a very vulnerable population. This is also the case for pregnant and post-menopausal women, whose hormonal upheaval leads to bone demineralization, increasing the risk of fracture, and for people with dark skin, for whom the synthesis of this vitamin through exposure to the sun is less effective.