• Vitamins are organic compounds necessary for growth, health, normal metabolism and physical well-being. Some vitamins are essential parts of enzymes -- the chemical molecules that catalyze or facilitate the completion of chemical reactions. Other vitamins form essential parts of hormones -- the chemical substances that promote and protect body health and reproduction.

• Vitamins are classified as either fat-soluble or water-soluble. The fat-soluble vitamins (which include Vitamins A, D, E, and K) require protein carriers for absorption. These vitamins can be stored in the body for use at a later time. These nutrients are usually found in the liver and fatty tissue. Vitamin C and the B vitamins are water-soluble. These vitamins are more easily lost through excretion and are more sensitive to the effects of storage and cooking.

• Vitamins can be obtained in "adequate" amounts from food sources, provided one eats a well-balanced diet made up of foods grown in nutrient-rich soil. However, there are many conditions and circumstances that make eating a well-balanced diet difficult, resulting in an inadequate vitamin intake. During such times, a vitamin supplement may be required. Some people, such as pregnant women, have special nutritional needs. Others, such as those with a restricted caloric intake, may be at risk for a vitamin deficiency. In these cases, supplements may be necessary to obtain optimal vitamin intake. Vitamin supplements are not meant to take the place of a good diet, but to enhance the benefits of a healthy lifestyle.