Coronavirus and Vitamin D: Correlation, Causation, and Confusion

F. Perry Wilson, MD MSCE
6 min readOct 28, 2020

The “lifestyle vitamin” has burned us before. Is Vitamin D supplementation smart in COVID-19?

I have a bit of a love-hate relationship with Vitamin D.

A brief search of my blog has shown me questioning the link between Vitamin D and multiple sclerosis, kidney disease, schizophrenia, falls, and childhood educational attainment.

So it’s no surprise, in the COVID-era, that Vitamin D comes up again. I was intrigued when Dr. Anthony Fauci, a sober and responsible voice if ever there was one during this pandemic reported his personal use of Vitamin D. Vitamin D was also part of the presidential cocktail that Trump received during his stay at Walter Reed.

I decided to dig into the data here, but before we do I want to tell you why I am inherently skeptical of Vitamin D studies. Two main issues:

1) Low vitamin D levels have been linked to so many things. Like, Vitamin C deficiency gets scurvy — fine, but low Vitamin D has been linked to everything from Alzheimer’s to Whooping Cough. It’s either the most important Vitamin in the world, or it’s a stand-in for some other important thing.

The second reason I’m a bit of a vitamin D skeptic is because when we’ve tested all these intriguing links via randomized trials, giving some people Vitamin D and some placebo, they almost always show no effect.

Me thinking vitamin D will help some condition

I feel a bit like Charlie Brown with the football here. Vitamin D has burned us before. A couple of examples.

Multiple observational studies found that people with low levels of Vitamin D were more likely to develop cancer and cardiovascular disease. These were good studies, adjusting for appropriate confounders, the whole deal.

Randomized trial of vitamin D supplementation looking at cancer and cardiovascular outcomes. Nothing.

Then we got a 26,000 patient randomized clinical trial. No effect on either outcome.

F. Perry Wilson, MD MSCE

Medicine, science, statistics. Associate Professor of Medicine at Yale University. New book “How Medicine Works and When it Doesn’t” available now.