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Vitamin D: An Evolving Star
By: Peter T. Pugliese, MD
Posted: June 29, 2009, from the July 2009 issue of Skin Inc. magazine.
page 6 of 11
Many foods, such as milk, yogurt, margarine, oil spreads, breakfast cereal and bread are fortified with vitamin D2 or vitamin D3 to minimize the risk of vitamin D deficiency. Fortified milk typically provides 100 IU per glass, and foods that contain vitamin D include cod liver oil—1 tablespoon provides 1,360 IU; cooked salmon—100 g provides 360 IU; and cooked mackerel—100 g provides 345 IU.
Vitamin D is formed in the skin from cholecalciferol produced by the action of UVB light on an earlier precursor. This compound undergoes changes that require modification by the liver and kidneys to produce the active form know as 1 α, 25 dihydroxy D3, or true vitamin D. Vitamin D is a hormone with receptor and transcription activity. It is known that in some cancers vitamin D is preventive. In the immune system, vitamin D has potent antiproliferative, pro-differentiative and immunomodulatory functions, including both immune-enhancing and immunosuppressive effects. In the skin, it has several functions that control epidermal proliferation by action on the keratinocytes. In addition, when the skin is irradiated with UVB, vitamin D stimulates the production of an epidermal peptide that is antimicrobial.
With all of these functions, the single most important one is the regulation of the level of calcium in the blood. It does this by its action on the parathyroid hormone and its role in calcitonin regulation. In the September 2009 issue of Skin Inc. magazine, the final part of this series will explore vitamin E.
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2. T Naveh-Many J and Silver, “Parathyroid hormone synthesis, secretion and action.” In Kidney Stones: Medical and Surgical Management. Raven, New York (1996) pp 175–199