More science is needed, but being deficient in vitamin D may make someone more likely to experience serious health complications if infected with COVID-19. Researchers analyzed all European studies from 1999 onward that measured vitamin D status among adults. The scientists then compared vitamin D levels with death rates from COVID-19. The study findings, published in Aging Clinical and Experimental Research, showed a statistically significant correlation between low vitamin D levels and mortality from COVID-19.
Populations where vitamin D deficiency is more common tend to experience higher infection and death rates from the virus. Shelter-in-place orders may have exasperated poor status for the sunshine vitamin. Low levels could also be a contributor to the high death rates in long-term care homes in countries like Canada. Despite lower amounts of sun UV exposure, Scandinavian nations—such as Norway and Sweden—tend to have less vitamin D deficiency, because of widespread supplementation; in turn, these nations have had fewer people with severe COVID-19 complications. Countries in the sunny Southern Hemisphere, including Australia, have relatively lower mortality rates (as I write this column). Beyond its role in bone health, vitamin D also supports the immune system through several immunity pathways—including, apparently, those involved in fighting this virus.
The study showed association, not causation. However, the authors suggest it’s likely that optimizing vitamin D levels in populations could help to reduce serious COVID-19 complications and death rates. Raising levels of vitamin D can be accomplished through sensible sun exposure, where possible; through dietary measures, such as eating fortified foods and vitamin D–rich fatty fish, like salmon and sardines; and through supplementation with about 1,000 IU of vitamin D daily, if needed. There is no data to support the use of excessive supplementation (4,000 IU or more).