Multivitamin. A pill, beverage, or other substance containing more than one vitamin.
Oxidation. A chemical reaction in which oxygen combines with a substance, changing or destroying its normal function. Oxidation can damage cell membranes and interfere with a cell's regulatory systems, but it is also part of our normal-functioning immune system.
Phytochemicals. Compounds found in fruits, vegetables, and other plants that can be health-protecting. Phytochemicals (sometimes called phytonutrients) include beta-carotene, lycopene, and resveratrol.
Prenatal Vitamins. Specially formulated multivitamins that ensure a pregnant woman gets enough essential micronutrients. Prenatal supplements generally contain more folic acid, iron, and calcium than standard adult supplements.
Recommended Dietary Allowance (RDA). The amount of nutrients needed daily to prevent the development of disease in most people. An example is vitamin C; the RDA is 70 milligrams, below which, for most people, there is the risk of developing scurvy.
Supplements. Vitamins, minerals, herbs, or other substances taken orally and meant to correct deficiencies in the diet.
U.S. Pharmacopeia (USP). A nonprofit authority that sets standards and certifies supplements that meet certain quality, strength, and purity standards, some of which are called the Good Manufacturing Practices (GMP). Many supplements carry the USP symbol on their label.
Vitamins. Naturally found in plants and animals, vitamins are vital to growth, energy, and nerve function. There are two types of vitamins used by the body to support health: fat-soluble and water-soluble.
Water-Soluble. Water-soluble vitamins like B-6, C, and folic acid are easily absorbed by the body. Your body uses the vitamins it needs, then excretes excess water-soluble vitamins in urine. Because excess amounts of these vitamins are not stored in the body, there is less risk of toxicity than with fat-soluble vitamins but a greater risk of deficiency.