Vitamin D Deficiency

Vitamin D (calciferol) has been recognized for almost 100 years as being essential for bone health, but also plays a variety of roles across the body. It's deficiency is becoming an increasingly important public health issue, though the definition of deficiency itself has become controversial. 90% of Vitamin D is formed in the skin through the action of the sun, and then activated by hydroxylation in the liver and then mainly in the kidney (but also prostate, colon, skin and osteoblasts) to 1,25-dihydroxyvitamin D. It interacts with specific receptors not only in the intestine and bone to regulate serum calcium levels and allow the normal development and mineralization of a healthy skeleton, but also in most tissues and cells. The extra-renally produced 1,25(OH)2D, working as an autocrine or paracrine hormone, elicits a wide variety of biologic responses, including regulation of cellular growth and modulation of the immune system. Prolonged deficiency leads to osteomalacia/rickets, and is also a risk factor for a variety of diseases (various cancers, autoimmune diseases, metabolic syndrome, type 2 diabetes, ischemic heart disease, and severe lower respiratory infections). Deficiency has long been recognized in areas of low sunshine, but was thought rare in sunny countries. However, D deficiency and associated osteoporosis and higher fracture rates in countries like <> and <> are surprisingly common and becoming commoner due to lifestyle factors (increasing indoor stay, use of sunscreens, limited skin exposure, etc.). Rickets/osteomalacia are re-emerging as a major public health problem in all age groups, but certain groups are especially vulnerable: those on anti-convulsants, anti-tubercular or immunosuppressive therapy, or thalessmics. Calcium deficiency may contribute to or be the major cause of nutritional rickets, because of financial or dietary reasons. Public health awareness of the importance of adequate vitamin D and calcium intake is needed, with action needed by clinicians, educators, public health experts, and governments (fortification of foods).