Vitamin D has an essential
role in
calcium metabolism and
bone health.
Vitamin D3 or
cholecalciferol is synthesized from 7-dehydrocholesterol or
provitamin D3, by
sunlight ultraviolet radiation to the
skin. 7-dehydrocholesterol is subsequently hydroxylated in the
liver and then in the
kidney to produce 1,25-(OH)2D3, the active metabolite that binds to specific receptors (VDR) in target
tissues, mainly
bone and
intestine. Other
tissues, such as the immune and
cardiovascular system, have also VDR.
Vitamin D deficiency can induce
rickets in
children and
osteomalacia and
osteoporosis in
adults. A possible inverse
association between
vitamin D levels and the
prevalence of
metabolic syndrome has been proposed.
Vitamin D deficiency increases the
risk of
type 1 diabetes,
insulin resistance, and
hypertension, key components of this
syndrome. However, other studies have not confirmed this
association. Further clinical and
experimental studies are needed to ascertain the
role of
vitamin D in
metabolic syndrome.