Advice circulating in traditional and social media to take vitamin D supplements to help stave off the coronavirus may be premature. The risks associated with taking more vitamin D are low, but there is the very real risk of raising false hope. Indeed, some of the researchers producing the studies linking vitamin D deficiency and coronavirus mortality rates warn against drawing sweeping conclusions about the benefits of taking the supplement.
Entertainment mogul Tyler Perry, for instance, on Instagram urged black people to use vitamin D because he had “read in a study out of Spain, Italy, and China … that a lot of people who died from COVID were low in vitamin D.”
The suggestion that vitamin D deficiency may be a source of vulnerability to the virus has also been given prominent distribution in outlets as varied as the nutrition industry news site Nutra Ingredients and the Wall Street Journal opinion page.
Yet, that advice is based on research that has serious data flaws.
Just prior to the spread of the pandemic, scientists with the Second International Conference on Controversies in Vitamin D released a consensus statement stating the methods used to test for vitamin D levels were “a critical and controversial issue.”
One reason for the controversy is that methods of testing vitamin D are often inconsistent, yielding very different results.
“The measurements of vitamin D are not standardized even within countries, so no blanket statement can be made about the validity of any specific countrywide measure,” said Dr. Robert Adler, one of the authors of the consensus statement. Adler, the chief of Endocrinology and Metabolism at the McGuire VAMC/Central Virginia VA Health Care System, told the Washington Examiner the preferred method for collecting vitamin D is one that separates liquid in a blood sample, uses two mass spectrometers, and follows standards developed by the National Institute of Standards and Technology. “These are available in many countries, but they are more expensive,” said Adler.
In the study cited by Perry, in which researchers from Northwestern University and Boston Medical Center found that nations with higher COVID-19 mortality rates had lower levels of vitamin D, some of the data from Italy were not collected using the preferred method.
The comparability of vitamin D tests also depends on when the tests are conducted, as vitamin D levels in human beings vary considerably depending on the season. “It will be highest at the end of summer and lowest at the end of winter, in general,” said Adler. In the Northwestern study, the data from France got collected during winter 2016, while in Iran, data collection occurred at both an autumn/winter period and a spring/summer period.
In short, there is no guarantee that vitamin D data collected in one nation is comparable to data collected in another.
Indeed, researchers warn that the public shouldn’t yet derive conclusions from this research. “It is still too early to comment on vitamin D as a possible co-treatment for COVID-19,” said Dr. Paul Lips of the Amsterdam University Medical Center, who has studied vitamin D testing extensively.
Dr. Cristian Ilie, research director at Norwich University Hospital and the co-author of a widely circulated study from the Queen Elizabeth Hospital Foundation Trust and the University of East Anglia finding a link between mortality and vitamin D deficiencies, acknowledged that his study had limitations. “We just wanted to describe our findings, which should be obviously validated in larger, different design studies,” he said to the Washington Examiner.
“I think one would need to do a placebo-controlled, randomized study” before advising vitamin D as a way to combat COVID-19, Dr. Vadim Backman, a professor of medicine at Northwestern University told the Washington Examiner. “My hope is that our work will help initiate such studies,” said Backman, who is also a co-author of the study touted by Perry.
To be sure, the risks of taking vitamin D appear to be low. It is possible that advising the public to take vitamin D could generate a shortage, much like that of toilet paper, making it harder for those with vitamin D deficiencies to find it. But it seems unlikely. “When I was last in the store, there was plenty on the shelves, and the price is fairly low,” said Angela Dowden, a registered nutritionist and writer at the conservative American Council on Science and Health. There are some serious health risks associated with the overuse of vitamin D, such as kidney problems and calcified blood vessels, but those are associated with long-term overuse. And it should be noted that much research does show that vitamin D can protect against the effects of other types of viruses.
Furthermore, there is newer research using different methods that suggests vitamin D may protect against COVID-19. Research conducted by Dr. Mark Alipio of the University of Southeastern Philippines examined 212 patients in the Philippines instead of using testing results from multiple countries. He found that patients with severe COVID-19 symptoms were much more likely to have low levels of vitamin D.
Yet Alipio was cautious about the findings. While he wrote that “vitamin D supplementation could possibly improve clinical outcomes of patients infected with COVID-19,” he counseled that “further research should conduct randomized controlled trials and large population studies to evaluate this recommendation.” Such research is likely a long way off, as randomized controlled trials are expensive and time-consuming.
