There are several studies and scientific publications that emphasize the importance of having a good level of vitamin D in the blood as a preventive method against coronavirus. For example this, this and this. They describe the clinical experience during the harshest months of the first wave of COVID-19, in which it was found that patients with high levels of vitamin D had a lower rate of worsening than those with deficiency.
In general terms, being well vitaminized will always help us fight diseases much better, both infectious and physiological, as pointed out by the anti-COVID-19 coordinator of the United States, Anthony Fauci. Now, in the case of vitamin D, its role seems especially relevant in diseases of the respiratory tract. Not in vain does the WHO recommend supplementation to prevent diseases of this nature in children in areas with malnutrition.
In the publications cited above, several directions of action of this vitamin in its action against COVID-19 are pointed out. A first and more generalist one is the modulation of the immune -defensive- response of the organism against the virus, so that it prevents the disease from flourishing.
On a more specific level, vitamin D acts as a modulator of the production of cytokines, a type of protein that triggers an immune response that if uncontrolled can lead to lethal autoimmune reactions, which attack the body itself, damaging organs and leading to the death.
The so-called cytokine storm is considered to be the leading cause of death among young people in the Spanish flu. Therefore, it is important that there is a vitamin / hormone that regulates the production of these proteins. Thus, with high levels of vitamin D, there is a control by the body of the immune response, while this is strong.
The mention of vitamin D is very relevant for two reasons: we are facing a second wave of infections that we do not know how far it will go in extension and intensity, and the entry of autumn exposes us to a general decrease in defenses, among other things by the descent of the hours of sun.
It is public knowledge that one of the most important ways to obtain vitamin D is to sunbathe in moderation, since UVB ultraviolet rays break down a cholesterol molecule when they hit the skin to give rise to calciferol, the inactive form of the vitamin. D of animal origin, also called vitamin D3.
Against this there is also the form of vitamin D2, or ergocalciferol, of vegetable origin, which appears in the vast majority of vitamin supplements. But the activation of both vitamins is not identical; While D3 is massively activated, D2 does so in a much more limited way, which is why supplements of plant origin are more ineffective in maintaining levels of activated vitamin D or calcitriol (1,2,5-dihydroxycholecalciferol).
This fact explains why we are a country in which despite having more hours of sunshine than anyone in Europe, there is an established deficit of vitamin D: we have poor nutrition and in winter we take little sun, with which one in seven Spaniards present avitaminosis, a clear risk of a deficient defensive response to COVID-19.
Natural sources of vitamin D
Besides sunbathing, there are other sources to get vitamin D. One already mentioned is supplements, but there is enough scientific evidence that if they are not of animal origin, they are quite ineffective, so, for example, it pushes people vegans to have to sunbathe in less comfortable times for this purpose.
The most direct, except for the sun, will thus be food. As has been said, D3 is obtained only from products of animal origin, with vegetables in their natural state being a zero source of vitamin D; D2 in supplements is achieved by hyperradiating vegetable leaves with UVA rays. Therefore the natural sources of vitamin D3 will be animal foods.
The most prominent are:
Dairy: as vitamin D is a fat-soluble molecule, which dissolves in fat, it finds a reliable source in whole milk.
Despite the fact that it is a heat-sensitive vitamin, pasteurization or UHT treatments do not entail a quantitative loss of vitamins, so it is not necessary to resort to raw milk, as some groups advocate.
Cheeses and yogurts that keep their fats intact are also a good source. As well as butter and cream.
Egg: we must actually say “egg yolk”, since it is in this part and not in the white where the vitamin D resides. A raw yolk contains 218 IU, when the average needs are 600 IU for adults and children older than one year.