Vitamin D and Its Impact on Covid-19

What might have happened if football stadiums had been set up last summer to do mass testing for vitamin D deficiency, with health departments standing by to give clear advice on how to supplement safely (do NOT overdose!!!!) and effectively?

How many COVID-19 hospitalizations and deaths might have been prevented by such a move?

Does that sound crazy? Hang on to your horses; we found out that there is evidence of a link between Vitamin D deficiency and COVID-19 severity and/or death.

Actually, several links.

A study last October found that 80% of hospitalized Covid cases were vitamin D-deficient:

"So what?" you ask. "Vitamin D is common in the general population. What about the people with known susceptibilities to COVID -- the elderly, smokers, people with chronic lung disease, the obese, people with blood clotting issues? Why would vitamin D deficiency have anything to do with THEIR COVID-19 cases?"

Why, indeed? Read on.


"Increasingly, VD [Vitamin D] deficiency is associated with several known geriatric syndromes."

"Thus, hypovitaminosis D is common world-wide, but is more common and more severe in older people. Non-classical effects of vitamin D, depending on serum circulating 25-hydroxyvitamin D concentrations, are present in most non-bony tissues; disorders associated with hypovitaminosis D include increased risks of sepsis [bacterial, mycobacterial and viral], cardiovascular and metabolic disorders [e.g. hyperlipidemia, type 2 diabetes mellitus, acute vascular events, dementia, stroke and heart failure]. Many cancer risks are associated with vitamin D inadequacy, though causality is accepted only for colo-rectal cancer."

"Ok, fine, that explains that the elderly may be much more likely to be vitamin D-deficient than the rest of the population," you say. "But what about smokers?"

Funny you should ask.


"Vitamin D deficiency was associated with lower lung function and more rapid lung function decline in smokers over 20 years in this longitudinal cohort of elderly men."

And not just elderly men:

"Tobacco smoke exposure is an independent predictor of vitamin D deficiency in US children."

"Cigarette smoke decreases the production of the active form of vitamin D (1,25-dihydroxyvitamin D) in lung epithelial cells, which may be overcome with higher serum levels of the substrate (25-hydroxyvitamin D). Additionally, cigarette smoke may affect expression levels of the vitamin D receptor."

"OK, fine, so smoking can decrease your vitamin D levels, and OF COURSE, people should quit smoking," you say, " but, come on, OBESITY doesn't have anything to do with vitamin D deficiency."

Oh, yes, it does.


"New research adds to the evidence linking obesity with lower levels of vitamin D, and the finding could help explain why carrying extra pounds raises the risk for a wide range of diseases, researchers say."

Did you see where it says, "ADDS to the evidence?" So, apparently, this association has already been known for quite a while.

"Wow," you say, after you pick up your jaw from where it dropped to the floor. "But what about blood clotting issues? I heard that blood clots in people with COVID-19 can be deadly. But how is that related to Vitamin D deficiency?"

Well, there are many causes of blood clots. But this gets VERY interesting...


"Vitamin D has been shown to have an anticoagulant effect. A decrease in 25-hydroxyvitamin D [25(OH)D] concentration has also been associated with an increased risk of venous thromboembolism."

"Wow ... so let's go back to Vitamin D and COVID-19. Was it only that one study on Vitamin D and COVID-19?" you ask.

Not by a long shot.


"Patients hospitalized with COVID-19 have low levels of 25-hydroxyvitamin D"

"Vitamin D deficiency in COVID-19 Quadrupled Death Rate"

"If vitamin D does in fact reduce the severity of COVID-19 in regard to pneumonia/ARDS, inflammation, inflammatory cytokines and thrombosis, it is our opinion that supplements would offer a relatively easy option to decrease the impact of the pandemic."

"Vitamin D and COVID-19: evidence and recommendations for supplementation"

It turns out, other studies have found that using vitamin D as a TREATMENT for Covid patients significantly reduced both ICU admission and mortality: and

This is NOT a wild new idea; it's been known for years that vitamin D deficiency is a leading susceptibility factor in acute respiratory tract infection, as this review of other studies shows:


But, given the weight of the evidence, we must ask: might some -- or many -- Covid hospitalizations and deaths have been avoided if health officials had just urged everyone to make sure their vitamin D levels are sufficient?

In the interest of thoroughness, we also point out that we did find a study that actually concluded that vitamin D supplementation had a NEGATIVE effect on COVID-19 outcome -- but the patients involved were not given vitamin D until they had ALREADY been admitted to the ICU, and they were given a whopping dosage of 540,000 IU. (Our understanding is that this is about 6,000-60,000 times the standard OTC supplement dosage.)

We recommend that you ask your doctor about determining whether you should be tested for vitamin D deficiency, and what your optimum levels and dosage should be.