Have a question? Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to hydroxyvitamin D [25 OH D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,dihydroxyvitamin D [1,25 OH 2 D], also known as calcitriol [ 1 ]. Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts [ 1, 2 ].
Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. While the sun is a potential source of vitamin D, the AAP advises keeping infants out of direct sunlight and having them wear protective clothing and sunscreen [ 34 ]. It is also important to note that vitamin D supplementation should be individualized based upon a particular individuals ability to regularly maintain a satisfactory level. We read enough medicine bottles to have a fair understanding of milligrams. How the Test will Feel.
Recent evidence for the nonskeletal effects of vitamin D, coupled with recognition that vitamin D deficiency is common, has revived interest in this hormone. Vitamin D is produced by skin exposed to ultraviolet B radiation or obtained from dietary sources, including supplements. Persons commonly at risk for vitamin D deficiency include those with inadequate sun exposure, limited oral intake, or impaired intestinal absorption. Vitamin D adequacy is best determined by measurement of the hydroxyvitamin D concentration in the blood. Average daily vitamin D intake in the population at large and current dietary reference intake values are often inadequate to maintain optimal vitamin D levels. Clinicians may recommend supplementation but be unsure how to choose the optimal dose and type of vitamin D and how to use testing to monitor therapy. This review outlines strategies to prevent, diagnose, and treat vitamin D deficiency in adults. Vitamin D has been appreciated for its role in calcium homeostasis and bone health since its identification in