To begin any series on a topic, the general terms of that topic should be discussed so readers will be able to follow the thread of the discussion. For the next several months, this column will be covering Vitamins and Minerals in some depth, covering the uses, sources, side effects, and research done concerning each.
Vitamins are organic compounds that the body requires in order to properly function. They are essential for continuance of life (utilized in small quantities) though most cannot be synthesized in the body. Contrary to popular belief, vitamins cannot be metabolized in the body to produce energy, however some (the B complex vitamins) are necessary for energy production. Vitamins are utilized in a regulatory manner rather than in a structural function.
Every vitamin is consumed in the food we eat, though a few can be synthesized to some degree in the body. Vitamin D is one that can be manufactured from a cholesterol derivative when the skin is exposed to sunlight and Niacin(a member of the B complex) can be manufactured from the amino acid tryptophan.
Still other vitamins are ingested in their precursor, or pro-vitamin form where they are then converted to the final vitamin product, within the body. The most widely known pre-vitamin is Beta Carotene which is converted inside the body to vitamin A. Though referred to as a single entity (Vitamin A or Vitamin B1), most are combinations of chemically related compounds.
Vitamins are separated into two major groupings called Fat-Soluble and Water-Soluble vitamins. The fat-soluble group contains vitamins A, D, E, and K, and Beta-Carotene.). The rest of the vitamin family, B-Complex's and Vitamin C comprise the water soluble family. The chemical entities Choline and Inosital are possible vitamins, though there remains some doubt as to their actual status.
The fat soluble vitamins are dependent on protein carriers in the blood and are not readily excreted from the body. They are stored within the body in the liver and fatty tissues. Vitamin D and preformed A have a distinct propensity toward toxicity. The water soluble vitamins not used by the body are excreted in the urine. One exception to the rule is vitamin B-6, pyridoxine, a member of the B-Complex family, that also displays a potential for toxicity as does A & D.
The recommended daily allowances (RDA's) are suggested amounts of essential vitamins and minerals considered adequate for the bodily needs of healthy people. The guidelines currently seen on all labeling were established by the Food & Nutrition Board of the National Academy of Science's, National Research Council, a group of researchers and nutritionists chartered by congress. RDA's are revised approximately every 5 to 10 years based on the then current information. There are current revisions in the works which will represent serious revisions.
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