> This says nothing about Vitamin D as a cure once you got infected.
I mean, yeah. There is literally nothing in the study, or literally any of the research I've read, that says anything about vitamin D being a benefit after you get infected, so I'm not sure why one would appear to think that's implied. It's like saying "Hey, this study isn't as strong as you think, because this study says nothing about vitamin D increasing your IQ."
The "correlation is not causation!!" bromide, while useful to understand in context, is overused, often given with examples that are more likely to be outlandish, with no backing evidence, than with a more straightforward explanation. As others have commented, there is evidence that vitamin D itself has a protective effect.
> The "correlation is not causation!!" bromide, while useful to understand in context, is overused.
Maybe then we should take a look at an actual double blind randomized controlled trial. Preferably one with thousands of participants. Luckily, exactly such a trial just ended. It lasted 5 years, it started in 2016 and ended in 2021. It considered acute respiratory infections; Covid was not one at the beginning of the trial, but was by the end of it.
Here's the conclusion:
Monthly bolus doses of 60 000 IU of vitamin D did not reduce the overall risk of acute respiratory tract infection, but could slightly reduce the duration of symptoms in the general population. These findings suggest that routine vitamin D supplementation of a population that is largely vitamin D replete is unlikely to have a clinically relevant effect on acute respiratory tract infection.
For me the key words in this conclusion are “[…] largely vitamin D replete” but for example, during winter in the Northern hemisphere, are we as a population really Vit. D replete?
My understanding that, at least in the UK, vitamine D deficiency is relatively common.
As someone born and raised in sunny southern Europe, my GP prescribed Vitamin D supplements to take indefinitely because I had a deficiency after ten years in the UK.
Anecdotally they seemed to improve both my mood and my general health.
This is in Australia, the placebo group had no deficiency in the first place. By contrast, deficiency is commonplace in the northern hemisphere during winter.
Furthermore, other studies suggest that daily supplementation is superior to monthly boluses, as far as I remember.
> The "correlation is not causation!!" bromide, while useful to understand in context, is overused, often given with examples that are more likely to be outlandish
I beg to differ. In fact way too many times people fall afoul of the ecological fallacy and it takes a bloody long time to be noticed.
Vitamin d deficiency is correlated to lower physical activity. We know health is correlated to Covid-19 outcomes. You need a double blind study to say there is evidence that it has a protective effect.
> This says nothing about Vitamin D as a cure once you got infected.
I mean, yeah. There is literally nothing in the study, or literally any of the research I've read, that says anything about vitamin D being a benefit after you get infected, so I'm not sure why one would appear to think that's implied. It's like saying "Hey, this study isn't as strong as you think, because this study says nothing about vitamin D increasing your IQ."
The "correlation is not causation!!" bromide, while useful to understand in context, is overused, often given with examples that are more likely to be outlandish, with no backing evidence, than with a more straightforward explanation. As others have commented, there is evidence that vitamin D itself has a protective effect.