Trying to sort out the things that make us most vulnerable to the COVID-19 pandemic virus is sometimes an obvious task.

For example, if you spend a lot of time in a room with a known COVID-19 patient who is coughing and breathing rapidly while you are not wearing a mask or other personal protective equipment (PPE), your chance of being infected with the virus are much greater.

That would be obvious to most of us and is the reason that we are pursuing contact tracing after a positive COVID-19 test is reported. However, there are risk factors that might not be so obvious.

One of these recently studied factors involves low plasma vitamin D levels, which has emerged as a possible independent risk factor for COVID-19 infection and hospitalization according to a large, population-based study.

Participants positive for COVID-19 were more likely to have low versus normal vitamin D levels in a multivariate analysis that controlled for several other factors.

One of the authors of the study suggests that the take home message for physicians is to test patients’ vitamin D levels and keep them optimal for the overall health as well as for a better immuno-response to COVID-19. But I am not ready to buy into the suggested connection yet.

Previous and ongoing studies are evaluating a potential role for vitamin D to prevent or minimize the severity of SARS-CoV-2 infection, building on years of research addressing vitamin D for other viral respiratory infections. The evidence to date regarding COVID-19, primarily observational studies, has yielded mixed results.

Multiple experts point out the limitations of observational data, particularly when it comes to ruling out other factors that could affect the severity of COVID-19 infection.

The recent study included data for 7,807 people, of whom 10.1% were COVID-19 positive. They looked at electronic health records for demographics, potential confounders, and outcomes between Feb. 1 and April 30.

A higher proportion of COVID-19 positive patients had low plasma vitamin D concentrations, about 90% versus 85% of participants who were negative for COVID-19. The difference was statistically significant, but not an enormous difference in my way of thinking.

The researchers also linked low plasma vitamin D level to an increased likelihood of hospitalization for COVID-19 infection.

The large number of participants and the population-based design are strengths of the study. But there are certainly limitations as well.

The researchers plan to try to decipher the potential role of vitamin D in prevention and/or treatment of COVID-19 through three additional studies. Also, they would like to conduct a meta-analysis to combine data from different countries to further explore the potential role of vitamin D in COVID-19.

Because the research looked back on observational data, a causative link between vitamin D levels and COVID-19 risk cannot be interpreted from the findings.

In the end, only a well-planned and randomized study can tell us whether vitamin D supplementation helps lessen COVID-19 severity, which is the reason that I am bringing this study to your attention.

When I read the title of this study and some of the comments of the researchers, it seemed to me that there might be some marketers of vitamin D supplements who will want to sell you their products based on the idea that it will help to protect you from the pandemic virus.

This study is not evidence for a claim like that. However, it does not rule out the idea that low vitamin D levels may be a problem for your health and well-being.

So, at this point in the pandemic, I recommend that you make sure to go outside in the sunshine regularly and make sure your diet contains foods containing vitamin D. The sun will help you make the most of the vitamin D you consume and the fresh air might do you some good psychologically as well.

Dr. Terry Gaff is a physician in northeast Indiana. Contact him at drgaff@kpcmedia.com or on Facebook. To read past columns and to post comments go to kpcnews.com/columnists/terry_gaff.

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