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Since the beginning of the COVID-19 pandemic, many people have started taking vitamins and supplements to ensure that they have adequate levels of protection against the viral disease. Many experts have also come forward to say that certain supplements and vitamins do have protective properties. Vitamin D has also enjoyed popularity as a nutrient that can protect against severe disease. However, contrary to popular belief, vitamin D may not actually provide protection from severe COVID-19 disease. Till now, there have been many observational studies that suggest that increased vitamin D levels may offer some protection against COVID-19. But these studies were inconclusive and, according to some experts, also possibly subject to confounding. Now, we have a new study from the McGill University in Quebec, Canada,, which suggests that genetic evidence does not support vitamin D as a protective measure against COVID-19. This study is published in PLOS Medicine.
The ability of vitamin D to protect against severe COVID-19 illness is of great interest to public health experts but has limited supporting evidence. To determine the relationship between vitamin D levels and COVID-19 susceptibility and severity, researchers conducted a Mendelian randomization study using genetic variants strongly associated with increased vitamin D levels. Researchers analyzed genetic variants of 4,134 individuals with COVID-19, and 1,284,876 individuals without COVID-19 to determine whether genetic predisposition for higher vitamin D levels were associated with less-severe disease outcomes in people with COVID-19. These people were from 11 countries across the world.
The results showed no evidence for an association between genetically predicted vitamin D levels and COVID-19 susceptibility, hospitalization, or severe disease. This suggests that increasing circulating vitamin D levels through supplementation may not improve COVID-19 outcomes in the general population.
However, the study had several important limitations. This research did not include individuals with vitamin D deficiency. It is possible that patients who have a deficiency may benefit from supplementation for COVID-19 related protection and outcomes. Additionally, the genetic variants were obtained only from individuals of European ancestry. More studies are needed to determine the relationship of this vitamin with COVID-19 outcomes in other populations.
Researchers say that vitamin D supplementation as a public health measure to improve outcomes is not supported by this study. The study results also suggest that investment in other therapeutic or preventative avenues should be prioritized for COVID-19 randomized clinical trials. According to them, most vitamin D studies are very difficult to interpret since they cannot adjust for the known risk factors for severe Covid-19 (e.g. older age, institutionalization, having chronic diseases) which are also predictors of low vitamin D. Therefore, the best way to answer the question of the effect of vitamin D would be through randomized trials, but these are complex and resource intensive, and take a long time during a pandemic.
Researchers also say that Mendelian randomization can provide more clear insights into the role of risk factors like vitamin D because they can decrease potential bias from associated risk factors like institutionalization and chronic disease. In the past Mendelian randomization has consistently predicted results of large, expensive, and timely vitamin D trials. Here, this method does not show clear evidence that vitamin D supplementation would have a large effect on Covid-19 outcomes.
(With inputs from Agencies)