This could simply mean that metabolic syndrome is the reason these people die. My guess is it's not just a matter of going in the sun more or taking vitamin D s

This could simply mean that metabolic syndrome is the reason these people die. My guess is it's not just a matter of going in the sun more or taking vitamin D supplements. If you have a vitamin D deficiency in the tropics, or even elsewhere, it can be a symptom of kidney or liver or other metabolic issues. Supplemental vitamin D can fix the deficiency/insufficiency, but they may not cure the underlying cause.