I searched google scholar for “vitamin d meta analysis”. I skimmed the abstracts. These are some of the earlier results.
It seems supplements help but randomised controlled trials are needed: https://jamanetwork.com/journals/jamainternalmedicine/fullar...
“Vitamin D supplementation appears to reduce the risk of falls among ambulatory or institutionalized older individuals with stable health by more than 20%” http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.578...
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.
