VITAMIN D Introduction
Vitamin D is a fat soluble vitamin. Unlike other vitamins, human body synthesizes Vitamin D of its own following exposure to ultraviolet rays (UV rays) of Sunlight. Hence, it is also called as “Sunshine Vitamin”. Some of the foods and supplements we take are also fortified with Vitamin D.

Vitamin D obtained from sun exposure, food, and supplements is biologically not in active form and must undergo some changes in the body for activation. The first conversion occurs in the liver which converts Vitamin D to 25-hydroxy Vitamin D [25(OH)D], also known as calcidiol. The second conversion occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxy vitamin D [1,25(OH)2D], also known as calcitriol.

In people with dark skin, due to the presence of greater amounts of the pigment melanin in the skin, the ability of the skin to produce Vitamin D is reduced.

Vitamin D promotes calcium absorption and aids in normal mineralization of bone. Without sufficient Vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, Vitamin D also helps protect older adults from osteoporosis. In Adults, low levels of Vitamin D are linked to diabetes, high blood pressure, cardiovascular diseases and even cancer.

Vitamin D levels can be detected through a blood test. Serum concentration of 25(OH)D is the best indicator of Vitamin D status. It reflects Vitamin D produced by the body.
* Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).

** 1 nmol/L = 0.4 ng/mL

Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement to achieve recommended levels of intake.