I’m confused by this comment. There is evidence that Vit D deficiencies have all sorts of health impacts, and that supplements raise in-blood levels.
What other evidence is needed?
Most things related to vitamin D are just correlation. If you are weak and frail you may not get out much and won’t have so much vitamin D. That doesn’t mean giving you vitamin D will make you strong. I heard that most studies don’t show benefits from vitamin D a supplements but maybe I’m wrong.
Oral vitamin D supplementation between 700 to 800 IU/d appears to reduce the risk of hip and any nonvertebral fractures in ambulatory or institutionalized elderly persons. An oral vitamin D dose of 400 IU/d is not sufficient for fracture prevention. https://jamanetwork.com/journals/jama/article-abstract/20087...
High levels of vitamin D among middle-age and elderly populations are associated with a substantial decrease in cardiovascular disease, type 2 diabetes and metabolic syndrome. If the relationship proves to be causal, interventions targeting vitamin D deficiency in adult populations could potentially slow the current epidemics of cardiometabolic disorders. https://www.sciencedirect.com/science/article/abs/pii/S03785...
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At this point I got bored of looking at results (I omitted a few which only looked for correlations).
So while there is some evidence of some benefits for some people, I didn’t find evidence of vitamin d being the magic panacea that it sometimes feels it is claimed to be by people on the internet.
I think you need to add "among people with sufficient levels of vitamin D" to that statement.
It follows almost from definition that if you are deficient in something, supplementing that something is beneficial. There might be some exceptions, but then we've really just got deficient defined poorly or no effective method of supplementation.
