Early on in the COVID-19 pandemic, it became apparent that vitamin D played an important role and could help reduce incidence of positive tests, infection severity and the risk of hospitalization and death.
The evidence of benefit was so clear, I published a scientific review1 in the journal Nutrients at the end of October 2020, co-written with William Grant, Ph.D., and Dr. Carol Wagner, both of whom are part of the GrassrootsHealth expert vitamin D panel.
This paper, “Evidence Regarding Vitamin D and Risk of COVID-19 and Its Severity” — which you can download and read for free — ended up being the second-most downloaded Nutrients paper in the 12 months following its publication.
The study with the most downloads that year and the all-time highest number of views (178,562) for any Nutrients paper was another vitamin D study2 by Bhattoa et.al., which found vitamin D supplementation reduced the risk of both influenza and COVID-19 infections and deaths. One of the coauthors of my paper, Grant, was a coauthor on this paper as well.
Several other vitamin D papers topped the lists of views, downloads and citations as well, which was a testament to the fact that many were in fact paying attention to the data rather than blindly believing media claims that there was “no scientific basis” for the recommendation of vitamin D for COVID.
More Evidence for Vitamin D
Since then, mounting data have continued to support and strengthen the recommendation of vitamin D against COVID. One of the most recent pieces of evidence is a paper3,4 that assessed the effectiveness of vitamin D supplementation for the prevention of COVID-19 in frontline health care workers, published in the June 2022 issue of Archives of Medical Research.
A total of 321 health care workers in four Mexican hospitals were enrolled, all of whom tested negative for COVID at the start of the study. They were then randomly assigned to receive 4,000 international units (IUs) of vitamin D per day for 30 days, or a placebo. Along with Real-Time PCR testing, participants’ vitamin D levels and antibody levels were also measured at baseline and again on day 45.
Follow-up was completed by 192 participants: 94 in the treatment group and 98 controls, and the difference in infection rates was pretty impressive. Only 6.4% of those taking vitamin D tested positive for COVID during the trial, compared to 24.5% of controls. (The p-value was less than 0.001, and anything below 0.05 is considered statistically significant.)
The researchers concluded that lower infection risk was associated with an incremental increase in the blood level of vitamin D, independently of vitamin D deficiency. This means, even if an individual started out with deficiency and still had a deficient or insufficient blood level of vitamin D at the end of the study, as long as it went up a little bit, it had a protective effect….