Vitamins are chemicals that are vital for life, to the extent that absence of these chemicals will result in serious illness of one type or other. In the industrialized West, vitamin-deficiency diseases are very rare, you only need X amount of each vitamin (eating carrots will only improve your eyesight if you have a Vitamin A deficiency), and too much of some vitamins (called a megadose) can be toxic. Despite this, an enormous number of Americans take vitamin supplements daily, fueling a multi-million dollar industry. For more, see vitamin supplements.
|Vitamin name||Chemical Name||Structure|
|Vitamin A||Retinoids (retinol, retinoid and carotenoids)|
|Vitamin B5||Pantothenic acid|
|Vitamin B9||Folic acid|
|Vitamin C||Ascorbic acid|
|Vitamin D||Ergocalciferol and Cholecalciferol|
|Vitamin E||Tocopherol and Tocotrienol|
This is a relatively short list, and most of these items can be found in a normal diet without much effort.
Clearly there are situations when vitamin supplements can be useful, and there is a thriving industry supplying such pills.
However, many companies want to go further in marketing supplements, and arguing that there are other chemicals that are "vitamin like" or desirable for health. See pseudovitamin for some examples. In 1998, choline was found to be necessary for human nutrition and to probably meet the definition of a vitamin, making it the only true recent addition to the vitamin category; its actual status is still unsettled.
There are other substances besides vitamins also necessary for human nutrition. Essential chemical elements are classified as minerals, not as vitamins. Water, fats (and essential fatty acids), and proteins are also necessary, but are not vitamins because they are needed in large amounts. In general, a vitamin is an organic compound (not a single element) needed by the human body in small amounts that is not always synthesized by the body in sufficient amounts and must be obtained through the diet. Vitamins D and K, although synthesized in the body, remain classified as vitamins because outside sources of these are sometimes needed.