> Unsurprisingly there's no direct clinical evidence.

"We searched for trials and didn't find any"

Unsurprisingly, there haven't been any (completed) trials on this particular combination of novel disease and possible prevention/treatment yet.

I'm concerned that people conflate "no evidence for efficacy" with "it doesn't work" instead of "we don't know if it works". You always start out with "no evidence".

There are studies that put serum Vitamin D levels against COVID-19 outcomes and they show a highly significant correlation. That's not "causal evidence", but it should put you on alert, you shouldn't be waiting for 2021 for possible Vitamin-D trials to complete.

As the authors of that review are saying, you should be supplementing anyway, whether there is a causal relationship or not.

You would see tons of research going on if there was more money to be made with Vitamin D.

I don't see why, since vitamin D is not patentable. If you spend the money on research others can make money from it making you lose out. Same reason why herbs are not researched even though they've been used for medicinal purposes for thousands of years: you can't patent a plant.

very true.

This review found nothing, so they found ‘no clinical evidence on vitamin D in COVID-19.’ No evidence for and no evidence against.

‘We found no trials of vitamin D in COVID-19 that have reported results.’

‘As our searches returned no relevant results, [...]’

But keep on posting the paper though.

I think that's a poor summary of the paper, here's the rest of the abstract:

"There is some evidence that daily vitamin D3 supplementation over weeks to months may prevent other acute respiratory infections, particularly in people with low or very low vitamin D status. This evidence has limitations, including heterogeneity in study populations, interventions, and definitions of respiratory infections that include upper and lower respiratory tract involvement."

"The current advice is that the whole population of the UK should take vitamin D supplements to prevent vitamin D deficiency. This advice applies irrespective of any possible link with respiratory infection."

That doesn’t quite help the argument that there’s no connection, right?

The old adage applies here: absence of evidence is not evidence of absence.

However, evidence of absence is unlikely to be found as the vast majority of researchers tend not to bother publishing papers with negative results. So if an idea seems like it should have been researched already, but no research papers are to be found, it may very well be because the evidence of absence simply hasn't been shared.

I wonder how many papers give a negative result because p was found to be .049 or so. I'm recalling that thread here a while back debating whether the statistical critical value is too high.

.049 is a positive result with a threshold of .05 - lower numbers mean smaller chance of no relationship.

However, it is also the best predictor of "absence" the scientific method has to offer.

There are absences and then there are absences :D

Absence of evidence because you haven't tried much/ there's no data yet is not the meaningful kind.