Sunday, July 5, 2009

Vitamin D

Vitamin D! Yes, I am that excited. Also, ducks are funny. It’s all relevant.

Vitamin D is a steroid hormone synthesised from a cholesterol molecule into one of two forms, D2 (from plants) or D3 (via exposure to UV-B light or from fish oil). In order for either of these forms of Vitamin D to be useful to the body, they must be processed by the liver or kidney into its active form, 1,25-dihydroxycholecalciferol.

Vitamin D is responsible for mineral metabolism (including increasing calcium absorption) and bone growth.

Two major consequences of Vitamin D deficiency are rickets (softening and deformation of bone) in children and osteomalacia (same thing, different name) in adults.

Research has been looking into Vitamin D deficiencies, metabolic roles, and treatment outcomes in a wide variety of areas including cancer, Alzheimer’s, dementia, and depression (6, 7).

Toxicity of Vitamin D will not result from over-exposure to sunlight (though skin cancer may). Overdoses of dietary supplements can lead to serious liver and kidney side effects. Small overdoses over a long period of time accumulate in the body to produce toxic effects, whereas short-term or periodic large doses are safer (4).

It has been suggested, based on the fact that sunlight produces about 10,000 IU of Vitamin D, that the recommended daily dose of Vitamin D (200 – 400 IU) is too low and some doctors recommend increasing this dose up to a few thousand IU. Since D2 and D3 are different molecules and are metabolised differently, recommended dosing might be more complicated than simply saying Vitamin D. Some evidence exists that D2 is not as efficient as D3 (2), while other research indicates no differences in effectiveness (3).

Sources of Vitamin D include sunshine, fish oil or fat, eggs, and fortified dairy and cereals.

References: 1, 2, 3, 4, 5, 6, 7

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