Vitamin D and COVID-19: What’s the Connection?

In the hospital where I work, most COVID-19 patients get vitamin D (cholecalciferol) 1,000-2,000 IU daily, hoping it will help fight the virus infection. Vitamin D is cheap and we haven’t seen any adverse effects from it.

It seems pretty clear that folks with deficiency of vitamin D who then develop COVID-19, have worse than usual outcomes. The only way to know if you have a deficiency is to get a blood level test. I recommend to my loved ones that they take supplemental cholecalciferol during surges of COVID-19 unless they’re certain they’re getting enough sunlight to generate vitamin D, or have a normal blood level. (I’m not recommending that to you; I’m not your doctor.) The dose is 1,000 or 2,000 IU daily, depending on body weight and other factors. I have seen a few people, usually little old ladies, develop hypercalcemia (high blood calcium) if they take that much vitamin D plus a calcium supplement, and that can be a problem.

Here’s the abstract of a recent literature review article in Nutrition:

“Molecular studies have demonstrated the importance of the exacerbated immune response to SARS-CoV-2 infection, called the cytokine storm, in more severe COVID-19. The pathophysiology is complex and involves several homeostatic factors; among them, a deficit of vitamin D draws attention because of its high frequency in the population. Some evidence suggests that people with low serum vitamin D levels have worse outcomes, often requiring intensive care. This review analyzed the studies available in the global literature addressing the benefits of vitamin D in COVID-19, relating serum levels to the severity of the disease, and indicating vitamin D as a possible prophylactic and therapy in infection.”

Read the article’s introduction for a list of vitamin D’s role in fighting infection.

The authors conclude:

“To our knowledge, there is still no robust evidence of the prophylactic and therapeutic role of vitamin D in COVID-19, and more clinical trials are needed to prove its efficacy against infection. Considering that its pharmacologic safety profile is well known, it is prudent to keep its mean serum concentration > 30 ng/mL in people with COVID-19 and the susceptible population.”

Another recent study in Nutrition compared the prevalence of COVID-19 with the prevalence of vitamin D deficiency in 20 European countries. They found no association one way or the other:

“Our analysis concludes that available data on the prevalence of Vit D deficiency among the European population do not allow for concluding that it constitutes a strong risk factor in the COVID-19 epidemic. However, these findings are not in line with outcomes of similar research works published recently.”

In some of the countries in the study, over 50% of the adult population was deficient in vitamin D.

Bottom line for me: Vitamin D supplementation doesn’t seem to hold as much promise in suppressing COVID-19 as I thought it would.

Steve Parker, M.D.