Vitamins are organic substances found in food; people and animals need them in order to maintain life functions or prevent disease. About 15 different vitamin groups are necessary for the nutritional needs of humans. Only minute amounts are required to achieve their purpose, yet without them, life cannot be maintained. Some vitamins, including vitamins A, D, E, and K, are fat soluble, and are found in the fatty parts of food and body tissue. As such they can be stored in the body. Others, the most notable of which are vitamin C and all the B-complex vitamins, are water soluble. These are found in the watery parts of food and body tissue and cannot be stored by the body. They are excreted in urine and must be consumed on a daily basis.

Although vitamins were discovered early in the twentieth century, it was common knowledge long before that time...