editorial: what is the definition of vitamin d deficiency and who is considered vitamin d deficient? urgent need for a national consensus

Since early works on isolation and characterization of vitamin d by elmer verner mccollum and edward mellanby in 1900s, this molecule still seems mysterious. after several decades since discovery of the miraculous effect of cod liver oil in treatment of nutritional rickets, escalating number of reports provide a huge body of evidence for various effects of vitamin d on human body. the spectrum of vitamin d health effects is quite wide, from bone and muscles (so-called calcemic effects) to a variety of non-calcemic effects including cardiovascular, insulin function, adipogenesis, obesity, immunity and mental status. consequently, having an optimal vitamin d status has attracted a huge attention.