[Annual citations in the PubMed database on vitamin D were approximately 5000, this represents a doubling in the last decade and a 20% increase in the last year. There is renewed interest in vitamin D synthesis, metabolism and action. The two principal reasons for increased interest can be: 1. new knowledge regarding the nonhormonal, autocrine, and paracrine actions of 1,25-dihydroxylated vitamin D metabolites in man, 2. the worsening, worldwide trend to vitamin D insufficiency.
Clinical vitamin D research in last years has confirmed the presence of a worldwide problem of vitamin D depletion, a problem that appears to be worsening. Largescale population based studies bear out long-held concerns that low serum 25(OH)D levels are associated with a number of adverse outcomes in the human musculoskeletal, innate immune, and cardiovascular systems. In fact, low vitamin D levels are significantly associated with all-cause mortality in the U.S. population and Hungary respectively.
It is hypothesized that the global rise in incidence of obesity contributes to the worsening of the problem of vitamin D deficiency, amplifying adverse impacts on the host skeleton, immunoreactivity to microbes, and metabolic status.
Finally, it should be remembered that treatment of vitamin D deficiency has two phases: restoration of 25(OH)D levels up to more than 30 ng/ml; and maintenance of the serum 25(OH)D level in that range. The present upper level (UL) of vitamin D intake that is deemed to be safe (2000 IU/day) must be re-evaluated considering data acquired over the past 15 years.]