Vitamin D may protect against severe COVID-19, further research finds
Ambient ultraviolet B (UVB) radiation, which is key for vitamin D production in the skin, at an individual’s place of residence in the weeks before novel coronavirus (COVID-19) infection, was strongly protective against severe disease and death, according to new research from Trinity College Dublin and University of Edinburgh published in the journal Scientific Reports.
Previous studies have linked vitamin D deficiency with an increased susceptibility to viral and bacterial respiratory infections. Similarly, several observational studies found a strong correlation between vitamin D deficiency and COVID-19, but it could be that these effects are confounded and in fact a result of other factors, such as obesity, older age or chronic illness which are also linked with low vitamin D.
To overcome this, researchers were able to calculate “genetically-predicted” vitamin D level, that is not confounded by other demographic, health, and lifestyle factors, by using the information from over one hundred genes that determine vitamin D status.
The Mendelian Randomization is a particular analytical approach that enabled researchers to investigate whether vitamin D and COVID-19 might be causally linked using genetic data. Few earlier studies attempted this but failed to show a causal link. This could be because UVB radiation sunshine which is the most important source of vitamin D for majority of people was ignored, the researchers said.
For the study, researchers looked jointly at genetically-predicted and UVB-predicted vitamin D level. Almost half a million individuals in the United Kingdom took part in the study, and ambient UVB radiation before COVID-19 infection was individually assessed for each participant. When comparing the two variables, researchers found that correlation with measured vitamin D concentration in the circulation was three-fold stronger for UVB-predicted vitamin D level, compared to genetically-predicted.
The researchers found that ambient UVB radiation at an individual’s place of residence preceding COVID-19 infection was strongly and inversely associated with hospitalization and death. This suggests that vitamin D may protect against severe COVID-19 disease and death, they said.
Additionally, while the results from the Mendelian Randomization analysis weren’t conclusive, some indication of a potential causal effect was noted. Because of the relatively weak link between genetically-predicted vitamin D level that is used for Mendelian Randomization analysis, it is possible that the number of cases in the current study was too small to convincingly determine causal effect, but future larger studies are required.