Our skin is able to synthesize vitamin D with exposure to ultraviolet-B rays from the sun. The form of vitamin D produced by the sun is not biologically available until it undergoes two changes. The first, which takes place in the liver, converts vitamin D to 25-hydroxyvitamin D or calcidiol. The second, which takes place in the kidney, converts calcidiol to 1,2,5-dihydroxyvitamin D or calcitriol, which is the biologically active form. several factors such as sunscreen with a sun protection factor above 8, age, darker skin pigmentation, northern latitude greater than 40 degrees and the winter season reduce the production of vitamin D in the skin. Most vulnerable to low vitamin D status are breast fed infants, elderly and institutionalized individuals, obese individuals and African Americans of all ages.
Author: Sumana Rao | Posted on: July 10, 2015