Any of various organic compounds that are needed in small amounts for normal growth and activity of the body. Most vitamins cannot be synthesized by the body, but are found naturally in foods obtained from plants and animals. Vitamins are either water-soluble or fat-soluble. Most water-soluble vitamins, such as the vitamin B complex, act as catalysts and coenzymes in metabolic processes and energy transfer and are excreted fairly rapidly. Fat-soluble vitamins, such as vitamins A, D, and E are necessary for the function or structural integrity of specific body tissues and membranes and are retained in the body.
A Closer Look Although it has been known for thousands of years that certain diseases can be treated with specific foods, the scientific link between vitamins and good health wasn't made until the early 1900s by Polish-born American biochemist Casimir Funk. While studying beriberi, a disease that causes depression, fatigue, and nerve damage, Funk discovered an organic compound in rice husks that prevents the illness. He named the compound vitamine, derived from the chemical name amine and the Latin word vita, "life," because vitamins are required for life and were originally thought to be amines. Funk's compound is now known as vitamin B1, or thiamine. His research and discovery led him, along with English biochemist Sir Frederick Gowland Hopkins, to propose the vitamin hypothesis of deficiency, which stated that certain diseases, such as scurvy or rickets, are caused by dietary deficiencies and can be avoided by taking vitamins. Further research allowed scientists to isolate and identify the vitamins that we know today to be essential for human health. Vitamins include A, C, D, E, K, thiamine, riboflavin, niacin, B6, B12, folic acid, biotin, and pantothenic acid. Vitamins are distinguished from minerals, such as calcium, iron, and magnesium, which are also essential for optimum health.