New Data: Vitamin D Supplements Unlikely to Prevent COVID-19

Mendelian randomization helps to tease out causality, and there does not seem to be a causal link between Vitamin D level and COVID-19.

This week — we’re going to dive into the lion’s den once again with this study, appearing in PLOS Medicine, failing to show a causal link between Vitamin D levels and COVID-19 incidence or severity.

And I know this is one of those hot button COVID issues — I think it’s because we all really want there to be a cheap, easy way to avoid getting COVID or getting severe COVID. And, technically, there is — it’s a vaccine — but sure it would be nice if there were something we had a lot more experience with — I get that.

And the observational data was definitely compelling. People with low Vitamin D levels really do have worse COVID outcomes. Much worse.

But correlation isn’t causation. You’ve heard that before, but we rarely dwell on what it really means. Why is causation so important? It’s because if A causes B, then changing A changes B. When we ask if low vitamin D levels cause…