Meta study | Vitamin D protects against the coronavirus
We have already written a few times that vitamin D protects against the coronavirus. Those posts do not do justice to the persuasiveness of the entire scientific research into this subject published so far. The meta-study published by the Italian physician Fausto Petrelli in the Journal of Steroid Biochemistry and Molecular Biology does.


Petrelli and his colleagues found 43 studies on the effect of vitamin D status on coronavirus infection. A total of 621,601 subjects participated in the studies.Results
The risk of infection with the coronavirus was 26 percent higher in the group with a low vitamin D level. When the researchers looked at the subjects with a vitamin D level of less than 20 nanograms per milliliter, a low vitamin D level increased the chance of infection by as much as 50 percent.

A low vitamin D level increased the risk of serious complications during an infection by a factor of 2.6 percent. You can see this in the figure below. Click on it for a larger version.

A low vitamin D level increased the risk of death from the coronavirus by a factor of 1.22.Supplementation
The Italians found 6 studies in which researchers compared subjects with corona who took vitamin D with infected subjects who did not take vitamin D. It showed that supplementation reduced the risk of serious side effects by 73 percent.

In 7 studies, the researchers determined the effect of vitamin D supplementation on the risk of a fatal outcome of the infection. According to these studies, vitamin D supplementation reduced the risk of death by 59 percent.
An adequate vitamin D status has a positive effect in 2 ways during contamination with germs, Petrelli deduces from the published molecular studies. This shows that good vitamin D status "inhibits the expression of pro-inflammatory cytokines interfering with the TNF-induced NFkB1 signaling pathway, and [...] initiates the expression of interferon-stimulating genes deputed to antiviral response activating the IFN-alpha-induced YAK-STAT signaling pathway".

Simply put, an immune system that has enough vitamin D reacts more quickly and more effectively to viruses, reducing the risk of infection. If the virus does manage to infect the body, vitamin D makes that the severity of inflammation is kept within limits.
"Reduced vitamin D values resulted in a higher infection risk, mortality and severity COVID-19 infection", writes Petrelli. "Supplementation may be considered as preventive and therapeutic measure."

J Steroid Biochem Mol Biol. 2021 Mar 26;211:105883.