What’s the link between vitamin D and the risk of being infected by novel coronavirus? In recent months, several scientists have tried to shed light on this aspect and what has emerged, to date, is that vitamin D actually has a protective role by making the virus less aggressive in the host body. To confirm this, we can mention the very recent research published by a team of the University of Chicago in the prestigious JAMA journal (Meltzer et al, JAMA, Sep 2020). In this article, scientists go further and hypothesize, thanks to vitamin D, a reduction in the risk of being tested positive for the novel coronavirus but also a possible reduction in the transmissibility of the virus.
Scientists at the University of Chicago analyzed data from 489 patients who, in the last year prior to being tested for COVID, also underwent tests to assess vitamin D levels. All study participants were tested between March and April 2020 to evaluate a possible positivity to the novel coronavirus. Comparing the results, what emerged was that those who had a vitamin D deficiency, defined as less than 20 nanograms per ml, and who had not undergone any type of treatment to restore the vitamin D values ??were almost twice as likely to test positive for COVID than those who had normal vitamin D values. Not only that, the researchers did not observe any significant difference in risk between those who had always had adequate levels of vitamin D and those who, on the other hand, had a deficiency at the time of the analysis but used supplements, always under medical supervision, and diet in order to restore adequate levels of vitamin D (sources of vitamin D, in addition to the sun's rays, are also mushrooms, cheeses, some fish such as anchovies and mackerel and finally eggs).
As explained in the article, vitamin D strengthens the innate immune system, which is our first line of defense and the one that prevents the virus from continuing to the lungs. Not only that, vitamin D also influences the metabolism of zinc, which helps to inhibit viral replication. Therefore, vitamin D promotes the virus clearance, reduces the inflammatory response that produces symptoms and could also reduce the transmissibility of the virus. This could be the possible explanation why people with adequate vitamin D levels also had a lower risk of being tested positive for COVID, it's possible that their body, in case of infection, had already eradicated it.
However, as pointed out by the researchers themselves, even if these observations are very promising, especially in view of future treatments against the virus, other studies will have to be performed as at the moment it has not yet been possible to demonstrate the direct action of vitamin D on the novel coronavirus and the exact mechanisms.