Different Sources of Vitamin D

Vitamin D, in strict sense is not a vitamin (as per definition of vitamins are not synthesized in the body and must be supplied in the diet or supplements, but vitamin D can be synthesized in the body) and unique because it is derived both from dietary sources and sunlight.ID-10025831

  • Sunlight: Vitamin D is synthesized in the human body by the action of UV rays (ultra violet) on 7-dehydrocholesterol. The skin is store of large quantity of 7-dehydrocholesterol. Exposure to good quality of sunlight is very important as air pollution can filter large percentage of UV rays. Skin color if it is dark can be disadvantageous in this regard and black skin can filter up to 95 % of UV ray and hamper the formation of vitamin D from 7-dehydrocholesterol in the skin. So theoretically blacks of Africa and America can be at disadvantageous (there is advantage of black skin that black skin people rarely get skin cancer as their skin filters 95% of the harmful UV rays which are responsible for skin cancer) position as far as production of vitamin D in skin is concerned.
  • Food Sources of Vitamin D: Vitamin D is found only in the foods of animal origin. Liver, egg yolk, butter, cheese etc. are rich source of dietary vitamin D. fish liver oil is the richest source (though not consumed as food) of vitamin D. Foods that are artificially fortified with vitamin like milk, infant foods, cooking oils, ghee etc. are also rich source of vitamin D. Recently it has been found that human milk contain water soluble form of vitamin D (vitamin D sulfate) in good quantity.

Our daily requirement of vitamin D is 2.5 mcg or 100 international units (IU). 1 mcg (microgram) of vitamin D or calciferol is equal to 40 IU or 1 IU = 0.025 mcg. Some of the dietary sources of vitamin D and the content of vitamin D in that food are shown below:

    1. Halibut liver oil = 500-10,000 mcg per 100 grams
    2. Cod liver oil = 200-750 mcg per 100 grams
    3. Shark liver oil = 30-100 mcg per 100 grams
    4. Fish fats = 5-30 mcg per 100 grams
    5. Eggs = 1.25-1.5 mcg per 100 grams
    6. Butter = 0.5-1.5 mcg per 100 grams
    7. Milk = 0.1 mcg per 100 grams

Image courtesy of nuttakit / FreeDigitalPhotos.net

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