Vitamin D is often used to better shield against respiratory tract infections.
Some observational studies suggest that its supplementation may also aid in the prevention of COVID-19 infection and severe disease.
However, new research that used gene variants to model a randomized clinical trial suggests that higher vitamin D levels do not prevent coronavirus.
The concept that a low-cost, safe, and easily accessible supplement can help protect people from SARS-CoV-2 infection and severe disease is attractive.
However, there is conflicting evidence that vitamin D truly protects against COVID-19.
The vitamin is necessary for the maintenance of strong bones and muscles, but there is also evidence that it may provide some protection against respiratory infections.
Unreported research reveals a relationship between mean vitamin D levels in 20 European countries’ populations and the number of coronavirus cases and mortality rates in the countries.
Several types of research have revealed a link between vitamin D deficiency and following COVID-19 infection.
The researchers behind this study, however, stressed that only randomized clinical studies might provide definite evidence that vitamin D supplementation can prevent COVID-19.
This is due to the fact that observational studies, such as theirs, are vulnerable to two statistical problems known as “confounding” and “reverse causation.”
Confounding arises when another variable influence the outcome that the researchers have not fully accounted for. Older age and chronic disease, for example, affect not only a person’s vitamin D levels but also their risk of COVID-19.
When the outcome influences the variable under research, this is known as reverse causation. For example, Severe COVID-19 may lower a person’s vitamin D levels.
In a clinical trial, researchers overcome these issues by randomly assigning participants to receive either the treatment or a placebo, then monitoring their progress.