I'm asking this because vast majority of Indians, even if they eat nonvegetarian food, when tested for vitamin D3 level, tend to have astonishingly low levels if one goes by the reference levels. And, in most of these patients they find little real difference with starting vitamin D3 supplementation (of which I don't know how much role the placebo effect plays). So, my question is more fundamental: how were these reference levels arrived at?
Were they arrived at by correlating specific symptoms with vitamin D3 levels or by assessing the levels in a large (obviously, Western!) population and then applying the principles of mean +/- 2 SDs? Shouldn't there be India specific vitamin D3 levels? How can we say that 90 or 95% of Indians, who would be apparently healthy, are "vitamin D3 deficient" simply because we (perhaps) have adopted the western reference ranges with assay kits?
