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February 25, 2010

Vitamin D And The Skin

Vitamin D is one of the fat soluble vitamins; it plays an important role in maintaining the normal blood levels of calcium and phosphate which are needed for normal mineralization of bone, muscle contraction, nerve conduction and proper cellular function of the body, it also plays a role in the immune modulation and evidence suggest that it has an anti-cancer properties.

The skin plays an important role in the formation of vitamin D; vitamin D can also be obtained from certain food, and supplements. When we are exposed to sun, Ultraviolet B radiation (UVB) found in the sunlight will convert cholesterol (7-dehydrocholesterol) found in the skin to Vitamin D3 (Cholecalciferol), Vitamin D3 will be transported to the liver where it will be converted to Calcidiol (25 D3) and this is what is tested when we measure Vitamin D level in the blood, normal level is between 80 - 175 nmol/L. Calcidiol will be carried to the kidney and will be converted there to Calcitiol (1, 25 D3) which is the active form of vitamin D; it will be released to the circulation and will be carried in the plasma to the target organs. Vitamin D toxicity doesn't usually occur if we are exposed for a long period of time to sunlight and this is because once Vitamin D3 concentration produced in the skin reaches equilibrium, further Vitamin D3 produced will be degraded by the same Ultraviolet light that created it.

Sources of Vitamin D: 1- The main source of Vitamin D comes from the exposure of our body to sunlight (see above). 2- Food sources: like oily fish such as salmon and sardines butter, egg yolks, some food can be fortified with Vitamin D like milk and cereals. 3- Vitamin D supplements.

Vitamin D deficiency can happen as a result of inadequate exposure to sunlight, liver or kidney disorders that will interfere with the conversion of Vitamin D into the active form, diseases that limit its absorption from the gastrointestinal track and other causes. Vitamin D deficiency will lead to softening of the bones due to the impairment of mineralization, it will lead to Rickets in growing children and osteomalacia in adults, and it can also lead to osteoporosis in which the bone mineral density is decreased leading to an increased tendency for fracture.

Severe burn injury may be associated with vitamin D deficiency; therefore vitamin D supplement is given to these patients.

Vitamin D overdose usually happens if excessive doses are taken (prescription forms); the symptoms include nausea, vomiting, weakness, loss of appetite, diarrhea and excessive thirst.

Some factors might decrease the ability of skin to synthesize vitamin D and therefore extra vitamin D may be required, these factors are:

  1. Latitude and season: they influence the amount of UV light reaching the skin.
  2. Skin pigmentation: the darker the skin, the more melanin pigment is present and this pigment will absorb UV light leading to a reduce ability of the skin to produce vitamin D.
  3. Aging process: with age the skin gets thinner and this reduces the efficiency of vitamin D synthesis.
  4. The use of sunscreen: although sunscreen reduces skin damage by the sun, widespread use of sunscreens affects the synthesis of vitamin D.
