The potential of vitamin D to either prevent or protect against COVID-19 has attracted much interest but data from 24 European countries suggests no association between vitamin D status and any COVID-19 outcomes.
There has been much hype in both the medical and lay press about the value of supplementing with vitamin D as a means of protecting against COVID-19, either through preventing or reducing the risk of infection. Despite this enthusiasm, in an assessment of the available evidence by NICE in the UK, it was recommended not to provide vitamin D to either prevent or treat COVID-19 except as part of a clinical trial. Furthermore, in an analysis of the correlation between vitamin D levels and COVID-19 cases in 20 European countries, although a significant negative correlation was observed, the study also reported a non-significant correlation between vitamin D levels and death from COVID-19. In an attempt to further explore this relationship, a team from the school of medicine, faculty of health sciences, Aristotle university, Greece, looked at the problem from a different angle. The team collated statistics on COVID-19 infections, recoveries and mortalities from the worldometer website and data on vitamin D levels from a comprehensive review of the literature. However, rather than focusing on a “mean” vitamin D level in countries, which was the approached taken in previous studies, the team used the prevalence of vitamin D deficiency within each country, based on data from the last decade. The team determined this from a comprehensive search of the literature, including only studies that were population-based, in adults and where vitamin D deficiency was reported as a serum concentration < 20ng/ml. The final analysis involved exploring the relationship between the prevalence of vitamin D deficiency and variables such as the number of COVID-19 infections, recoveries and mortalities per 1 million population.
The researcher found that vitamin D deficiency was common throughout the 24 European countries studied. It ranged from 6% (Finland) to 75.5% (Turkey) and in 11 of the countries the data suggested that more than 50% of the population were vitamin D deficient. Cases of COVID-19 were found to be positively correlated with the prevalence of vitamin D deficiency although this was non-significant (Pearson’s correlation, r = 0.19, p = 0.374). Similarly, there was a non-significant correlation between vitamin D deficiency and recovery from COVID-19 (r = 0.31, p = 0.131) and death (r = 0.129, p = 0.549) per one million population. In discussing their findings the authors noted that their analysis shows how there was no apparent relationship between vitamin D deficiency among the European populations studied and COVID-19 infection, recovery or mortality. They concluded that vitamin D deficiency is not a strong risk factor for any of the outcomes associated with COVID-19.
Bakaloudi D, Chourdakis M. Prevalence of vitamin D is not associated with the COVID-19 epidemic in Europe. A judicial update of the existing evidence. MedRxiv 2021 doi: https://doi.org/10.1101/2021.03.04.21252885