How Food Works

Vitamins

The Merriam-Webster Collegiate Dictionary defines "vitamin" as:

vi.ta.min: any of various organic substances that are essential in minute quantities to the nutrition of most animals and some plants, act esp. as coenzymes and precursors of coenzymes in the regulation of metabolic processes but do not provide energy or serve as building units, and are present in natural foodstuffs or sometimes produced within the body.

Vitamins are smallish molecules (Vitamin B12 is the largest, with a molecular weight of 1,355) that your body needs to keep itself running properly. In How Sunburns and Sun Tans Work, we learn that the body can produce its own Vitamin D, but generally vitamins must be provided in food. The human body needs 13 different vitamins:

Vitamin A (fat soluble, retinol) comes from beta-carotene in plants; when you eat beta-carotene, an enzyme in the stomach turns it into Vitamin A.

Vitamin B (water soluble, several specific vitamins in the complex)

Vitamin B1: Thiamine
Vitamin B2: Riboflavin
Vitamin B3: Niacin
Vitamin B6: Pyridoxine
Vitamin B12: Cyanocobalamin
Folic Acid

Vitamin C (water soluble, ascorbic acid)

Vitamin D (fat soluble, calciferol)

Vitamin E (fat soluble, tocopherol)

Vitamin K (fat soluble, menaquinone)

Pantothenic acid (water soluble)

Biotin (water soluble)

In most cases, the lack of a vitamin causes severe problems. The following list shows diseases associated with the lack of different vitamins:

Lack of Vitamin A: Night blindness, xerophthalmia
Lack of Vitamin B1: Beriberi
Lack of Vitamin B2: Problems with lips, tongue, skin,
Lack of Vitamin B3: Pellagra
Lack of Vitamin B12: Pernicious anemia
Lack of Vitamin C: Scurvy
Lack of Vitamin D: Rickets
Lack of Vitamin E: Malabsorption of fats, anemia
Lack of Vitamin K: Poor blood clotting, internal bleeding

A diet of fresh, natural food usually provides all of the vitamins that you need. Processing tends to destroy vitamins, so many processed foods are "fortified" with man-made vitamins.