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| Proper name |
Cholecalciferol (vitamin D3) |
| Category |
Sterol hormone or pro-hormone depending on the form. |
| Functions |
Stimulates intestinal absorption of calcium and phosphorus and promotes
normal bone mineralization. May function in cellular reproduction and
cellular differentiation in tissues throughout the body. Appears to inhibit
melanoma, leukemia, lymphoma, cancer of the breast and colon. May treat
psoriasis. |
| RDA |
400 International Units in children and pregnant or lactating women, 200
IU in adults over the age of 24. |
| Therapeutic
dose |
400 to 800 IU per day. |
| Deficiency symptoms |
In children - Rickets, bow-legs, knock-knees, pigeon chest, malformations
of the skull, spinal curvature, tooth decay and orthodontic problems. In
adults Ð osteoporosis, osteomalacia, increased incidence of hip and other
fractures, muscle weakness, rheumatic pains, and ringing in the ears (due
to demineralization of the bones of the inner ear). |
| Toxicity |
60,000 IU has caused calcium deposits in the kidneys and soft tissue, muscle
weakness, bone pain and failure to thrive in children. |
| Best
forms
|
Cholecalciferol |
| Food
sources |
Grains, dairy products (they are fortified) and egg yolks. Sunlight stimulates
the production of Vitamin D in the skin. |
| Lab
tests |
Serum alkaline phosphatase is increased in Vitamin D deficiency. Radio
Immune Assay (RIA) can measure the active form of vitamin D |
| Drug
interactions |
Vitamin D may be depleted by taking Barbituates, Carbamazepine, Cholestyramine,
Cimetidine, Colestipol, Corticosteroids, Ethosuximide, Famotidine, Fosphenytoin,
Isoniazid, Methsuximide, Mineral Oil, Nizatidine, Phenytoin, Ranitidine,
Rifampin. |
| Nutrient interactions |
Is required for Calcium and Phosphorus absorption and metabolism. |
| Metabolism |
Vitamin D3 is produced
by the effect of ultraviolet rays from sunlight on a cholesterol compound
in the skin (7-dehydrocholesterol). Persons not getting much sun, or those
with heavily pigmented skin may fail to receive adequate ultraviolet radiation
in the deeper layers of skin. A carrier globulin protein takes D3 to
the liver where it is converted into 25-hydroxycholecalciferol. It is
then transported to the liver. In the kidney, the enzyme alpha-hydroxylase
converts the 25-hydroxycholecalciferol into the active form, calcitriol.
Being fat-soluble, vitamin D stores in the fat, especially the liver.
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