Thread by @Ayjchan

Been hearing a lot about using Vitamin D to fight COVID. Finally got around to reading the paper that is at the root of all this.

tldr the science is far from settled, but, yes, it should be considered for -elderly- patients with Vitamin D deficiency.

sciencedirect.com/science/articl…

First things first, the form of vitamin D used in this study is not the nutritional vitamin D you can buy off the shelf. The authors say as much in the paper: "Our study does not include a comparison with cholecalciferol, the native vitamin D3 form"

2nd, although patients were selected at random, the authors clarify this study was NOT double-blind placebo controlled. What this means: the doctors/organizers (and the patients) knew who was or was not receiving calcifediol (prehormone produced by hydroxylation of vitamin D).

3rd, and possibly most importantly, this study did NOT check for vitamin D deficiency in the patients before or after treatment: "Serum 25OHD (calcifediol) concentrations at baseline or during treatment are not available".

That means we don't know which patients were deficient!

4th, looking at the patient traits, the group that did not receive the calcifediol treatment was very significantly more likely to have/have had high blood pressure; 15 of the 26 patients had previous high blood pressure, which is a risk factor for severe COVID.

Plus, ~1 in 5 (=10/50) of the no-calcifediol group suffered from diabetes compared to 3/50 in the calcifediol-treated group. Another risk factor for severe COVID.

5th, the authors said "we did not collect the BMI, which would have allowed us to add obesity as a risk factor for severe evolution of COVID-19" --- we now know that obesity is a major risk factor, multiplying the risk of severe COVID.

6th, these patients had an average age of ~53 years in both treated and untreated groups. Meaning that if you're a young-ish healthy person without a vitamin D deficiency, this strategy probably does not apply to you.

In summary, due to how the study was designed, not controlling for major risk factors across the treated and untreated groups, the conclusions are far from solid. It would be dangerous for people to think that taking vitamin D will prevent development of severe covid.

So, is there a paper that actually looks at vitamin D deficiency and its effect on severe COVID?

Yes, there is, but it also suffers from caveats: journals.plos.org/plosone/articl…

Sorry, wrong paper, by the same group in the same journal, published in the same month; this is the one that looks at vitamin D deficiency and its effect on severe COVID: journals.plos.org/plosone/articl…

Keep in mind, this paper did not treat the patients with vitamin D, their objective was to compare how patients with or without vitamin D deficiency fared after catching COVID.

Important numbers from this study performed in Iran:

Patient mean age of 58.7 years; more than a third were >65 years old.

1 in 3 of their patients were vitamin D sufficient; two-thirds were vitamin D deficient.

3 in 4 of their patients had severe COVID.

This is the finding regarding vitamin D sufficiency and COVID severity: "The data analyses revealed that the severe disease infection was less prevalent in patients with vitamin D sufficiency (63.6% vs. 77.2% p = 0.02)."

63.6% vs 77.2% -- patient mean age of 58.7 years.

My interpretation of these papers is that it's probably not bad to make sure your vitamin D levels are adequate, BUT a cause-and-effect relationship between vitamin D levels and severe COVID has NOT been demonstrated.

Vitamin D cannot be used to sanction risky pandemic behavior.

I know everyone is desperate for a cure or prophylactic against COVID. It would be great if there was a magic pill that we can take and immediately not be vulnerable to (severe) COVID. But this is not it... maybe it helps a bit in elderly patients, but the data is inconclusive.

Although it probably won't harm people to eat Vitamin D supplements, these supplements are not a replacement for proper anti-pandemic measures.

For instance, infusing all nursing home members with Vitamin D is probably not going to save the majority from severe covid.