[haltingproblem]

The article "Is Sunscreen the new margarine" argues that "what made the people with high vitamin D levels so healthy was not the vitamin itself. That was just a marker. Their vitamin D levels were high because they were getting plenty of exposure to the thing that was really responsible for their good health—that big orange ball shining down from above." [1]. If this is true, we have mistaken coincidence due to a common latent cause for causation.

The article "Limits of Vitamin D supplements" is a summary of the Lancet meta-analysis: "Vitamin D status and ill health: a systematic review", which is paywalled [2]. The review shows that Vitamin D supplementation has no clinically beneficial outcome on heart disease, stroke, or cancer.

FWIW, I have been supplementing with Vitamin D for over a decade. I would rather like Vitamin D to work because I have chronically low levels and it would be good to have such a good silver bullet of a nutrient. I have not stopped my supplementation but I do take more frequent walks in the Sun.

[1] https://www.outsideonline.com/2380751/sunscreen-sun-exposure...

[2] (https://well.blogs.nytimes.com/2013/12/11/limits-of-vitamin-...)