Vitamin D deficiency in Indian adolescents.

In humans, the main source of vitamin D comes from photoconversion of 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D3) by solar ultraviolet radiation (UVB: 290-320 nm). Vitamin D formed in the skin or the small amount absorbed from the diet is hydroxylated at the 25 position to produce 25 hydroxyvitamin D (25OHD), which is considered to be a reliable index of an individual’s vitamin D status. Vitamin D is crucial for calcium homeostasis and musculoskeletal health. Adequate vitamin D status during adolescence might help to reduce the risk of osteoporotic fractures in later life. There is also a growing body of evidence linking vitamin D status with non-skeletal disorders including autoimmune disorders (Crohn’s disease, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes), infections, and risk of developing cancers of the breast, colon, prostate and ovaries(1).