There is no robust evidence vitamin D is effective in improving outcomes or preventing COVID. It's just the new ivermectin, HCQ etc.
The evidence for vitamin D is patchy and it’s a pity more and better research hasn’t been done yet. Taken as a body, however, there’s a fair suggestion that adequate vitamin D could be protective. We definitely need more but it looks reasonably promising overall.
And here’s the thing. We know already that the UK population as a whole tends to be low in vit d, at least in Winter. We know that low vit d affects immunity in general, so it’s not a massive leap to think it could be a factor with Covid severity.
Most people in the Uk could do with (greater) supplementation and even those toward the bottom of the normal range could supplement and raise their levels but still fall within the ‘normal’ range, just higher up in it.
The risks of over-supplementing are longer-term and easy to mitigate - with a simple and cheap finger prick blood test you can check blood levels easily. Just as easy as a PCR or LFT.
It’s cheap and easy to take.
So what’s the downside, when we all need to supplement for our health in Winter anyway?
I do think lack of profits plays a part. There are only so many trials that can be done by non-profit making bodies such as universities.
I also think the lack of interest in vitamin d is part and parcel of the general lack of interest in nutrition and deficiencies we see in medicine and hence it becomes easy to dismiss interest in vit d as ‘the new Ivermectin’ rather than be open minded.