Vitamins are micronutrients necessary to facilitate and regulate various physiological processes. A lack of vitamins may cause an imbalance resulting in diseases, deficiencies and severe complications. There are two types of vitamins: water-soluble, which are excreted in urine, and fat-soluble, which are stored in fat tissues. Most individuals obtain the necessary vitamins through dietary sources, but if you feel you need a vitamin supplement, check with your doctor.
Water-Soluble Vitamins
Vitamins that dissolve, or are soluble in water, are eliminated in your urine everyday and must be replaced everyday. Washing foods that contain water-soluble vitamins can reduce or eliminate the vitamins in the food. Improper preparation and storage of foods may diminish the vitamins' effectiveness. It is important to refrigerate fresh produce to preserve their vitamin content and keep milk and dairy products, as well as grains, from strong light sources. Water-soluble vitamins include vitamin C and the B-complex family of vitamins.
Water-Soluble Vitamin Doses
The Food and Nutrition Board of the Institute of Medicine establishes the recommended dietary allowance, RDA, or, if there is not sufficient information to establish an RDA, they set an adequate intake level, AI. The following are the daily RDAs or AIs for water-soluble vitamins for adults: vitamin C, 90 mg; biotin, 30 mcg; folic acid, 400 mcg; niacin, 16 mg; pantothenic acid, 5 mg; riboflavin, 1.3 mg; thiamine, 1.2 mg; vitamin B6, 1.3 mg; and vitamin B12, 1.4 mcg. Before taking vitamins, consult with your doctor.
Fat-Soluble Vitamins
Fat-soluble vitamins are stored in the fatty tissues of your body and your liver. Because they are excreted slowly over time, it is not necessary to replenish them on a daily basis. Unlike water-soluble vitamins, foods containing fat-soluble vitamins retain the nutrients during the storage and cooking processes. High doses of fat-soluble vitamins may cause toxicity and should only be taken on the advice of your physician.
Fat-Soluble Vitamin Doses
Fat-soluble vitamins include vitamin D. When exposed to sunlight, your skin synthesizes vitamin D. It can also be obtained from dietary sources, as can the rest of the fat-soluble vitamins, A, E and K. The daily RDA or AI for an adult for the fat-soluble vitamins are as follows: vitamin D, 600 IU; vitamin A, 3,000 IU; vitamin E, 22.5 IU; and vitamin K, 90 - 120 mcg. Before taking any fat-soluble vitamin, especially vitamin K, consult your physician first.
References
- University of Rochester: Vitamins
- Colorado State University: Water-Soluble Vitamins
- Linus Pauling Institute: Vitamins
- Colorado State University: Fat-Soluble Vitamins
- Food and Nutrition Board, Institute of Medicine: Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Vitamins
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