Originally Posted by
jfsully
Or maybe having another condition that lowers your vitamin D also raises your coronavirus risk?
As per usual, the headline does not match what the study actually shows. This study does not test whether taking vitamin D will lower your risk; it only showed that people with lower vitamin D are at higher risk. This sounds like it might be the same thing but it is not. To decide whether taking the supplement is useful, they would have to compare people who were taking vitamin D with people who were not taking it, and whether increasing serum level with the supplement affected your risk of covid.
There is good evidence that having an inflammatory condition lowers serum vitamin D levels. This would explain why low vitamin D shows up in so many different disease states. If it is an effect, not a cause, it also explains why vitamin D supplementation has so far failed to prove helpful in so many disease states. It would be like noticing that house fires generate a lot of smoke, and smoke is bad, and concluding that if your house is on fire you should bring in some fans to clear the smoke out. It won't help, although unlike the fans, vitamin D probably won't make things worse. So its certainly possible that many of the people in the "low vitamin D" category had other conditions that lowered their D and that also raised their covid risk. If that's the case, then taking vitamin D will not reduce your covid risk.
That being said, vitamin D is cheap and safe, and many of us, especially in the great frozen north, are near deficient, so it's OK to take it. But I doubt it will reduce your risk of getting coronavirus very much (and your risk should already be very low if you are careful and paying attention).