Wednesday, July 11, 2012
A vitamin can be defined as a substance which is soluble in either water or fat; which, though needed to maintain life, does not supply energy; and of which a deficiency results in various diseases. Scurvy, for instance, results from a deficiency of vitamin C; it was once a common disease among sailors, who had few fresh fruits and vegetables to eat. There are five forms of vitamin D, of which two (D2 and D3) are especially important, and in fact the label “vitamin D” normally refers exclusively to them, unless otherwise specified; and it is those two that we will discuss. Both forms are fat soluble. They are chemically classified as secosteroids, that is, steroids with a “broken” ring in their molecules. Vitamin D2 is derived from ergocalciferol (chemical formula C28H44O), and vitamin D3 from cholecalciferol (chemical formula C27H44O); they thus differ only in one carbon atom. In both forms, the vitamin is essential for calcium and phosphorus metabolism. A deficiency of vitamin D causes rickets, in which the bones become so soft that they bend abnormally and often develop knobs on them. The victim, most commonly a child, develops unnatural poses such as knock knees or bow legs, which usually remain when the bones harden later in life. It has also been postulated that a deficiency of vitamin D can be a factor in the development of multiple sclerosis. Certainly, the results of recent research strongly indicate that victims of that disease whose diet is low in vitamin D are more likely to relapse into it. Vitamin D2 can come only from plants. It aids in the production of insulin and helps the body fight tumors. Sunlight is the most direct source for this vitamin, so at least thirty hours of exposure should provide enough for the body to function. Foods high in vitamin D2 include egg yolks, boxed cereals, and fortified margarine. Vitamin D3 aids in the absorption of calcium by the bones. It too comes from sunlight, but here only ten minutes at most, without a powerful sunscreen, should be enough to provide the body’s needs. Foods high in vitamin D3 include the oils of such fish as mackerel, cod, tuna, pink salmon, and catfish. Beef liver and cheese also contain small amounts of the vitamin. Like all vitamins, D2 and D3 can be obtained in the form of pills. D3, however, is much more prevalent. Instructions on the label should be always be followed. Biologists do not agree on which form of vitamin D is more powerful, or if they are both equally so. But it is now known that they are not equivalent, for four reasons: (1) Vitamin D2 has a shorter shelf life. (2) They are not equally effective at raising the levels of serum 25- hydroxy vitamin D. (3) The metabolites of vitamin D2 do not easily bind to the plasma protein that binds vitamin D. (4) The metabolism of vitamin D2 is non-physiological. You can get a vitamin D test by going online to lifelinescreening.com, selecting the desired test, and bringing it to a local laboratory. The results should be in within 72 hours at most.