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Can vitamin D-efeat COVID-19?

Background

Several studies have found that vitamin D levels tend to be lower in patients who develop severe COVID-19 or die from it. However, it doesn’t necessarily follow that low vitamin D levels increase the risk for bad outcomes from COVID-19, as high levels of inflammation (like those caused by the virus) can reduce vitamin D levels. Even when pre-infection vitamin D levels are used as the comparison, people with chronic inflammation, or people who are less likely to engage in health-promoting behaviors like outdoor exercise or supplementation, may have both lower vitamin D levels and a greater susceptibility to COVID-19, without these two factors necessarily being causal. The way to determine whether or not vitamin D levels are relevant in COVID-19 is to conduct a supplementation trial.

The study

In this pilot randomized, open-label, controlled (but not placebo-controlled) trial, 76 patients who had been hospitalized due to COVID-19 took 0.532 mg of calcifediol upon admission (2/3 of participants), and 0.266 mg on both day 3 and 7, (1/3 of participants), or no vitamin D throughout the entire stay. All participants received standard treatment as well.

The results

The main outcomes of interest were the rates of ICU admission and death. Only 2% of the participants who took calcifediol required ICU admission, while 50% of the participants who did not take calcifediol required ICU admission. Two patients who didn’t take calcifediol died, while none who took it died.

Note

The trial was preliminary and limited in design, and lacked a placebo control. The lack of blinding could have opened up the trial to bias because it’s possible that participants were treated differently based on which group they were in, and it’s not clear whether or not the hospital staff determining ICU admissions were blinded to the different groups. There was a statistically significantly higher rate of hypertension in the control group at baseline, which could have easily made them more likely to die, and while not quite statistically significant, they were also more likely to have diabetes. The vitamin D group, on the other hand, included notably more patients who were immunosuppressed due to having had organ transplants, though this wasn’t statistically significant. Future trials including additional participants could prevent substantial baseline differences between groups and improve the accuracy of studies.

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