Recent literature on vitamin D is full of controversies regarding its measurement, benefits, diagnosis, and management of its deficiency. In addition to addressing the consequences of deficiency, benefits of its replenishment, and clinical recommendations for supplements, this review addresses extra-skeletal effects of vitamin D. Vitamin D is essential for skeletal health and prevention of falls and injuries. Vitamin D enhances intestinal calcium absorption and mineralization of osteoid tissues. Rickets in children and osteomalacia in adults are classic manifestations of severe vitamin D deficiency. Cohort studies suggest that low 25 hydroxyvitamin D [25(OH)D] affects numerous and diverse physiologic functions, such as control of cell growth including cancer cells, protection against autoimmune disorders, and muscular coordination. Emerging data also suggest that low vitamin D levels may worsen disorders, including cancer, metabolic syndrome, obesity and diabetes, infectious diseases, and autoimmune disorders. Whether increased incidences of these diseases are consequences of widespread vitamin D deficiency is to be determined. Moreover, many reported relationships between vitamin D deficiency and diseases are based on epidemiological observations. Measurement of serum 25(OH)D is the way to evaluate vitamin D status. Serum 25(OH)D levels below 20 ng/mL are considered deficient, whereas optimum levels are between 30 and 50 ng/mL. An additional 1,000 IU of vitamin D per day generally is sufficient for lighter-skinned individuals; elderly, obese, and dark-skinned individuals and other groups of patients may need an additional 2,000 IU or more per day to maintain physiologic serum 25(OH)D levels.
Sri Lanka Journal of Diabetes, Endocrinology and Metabolism 2012; 2: 73-88