2. Introduction

2.1 Definition of Vitamins

Vitamins are organic compounds which the body needs to function normally. They cannot be manufactured by the body (with few exceptions); therefore, they must be supplied by food. In their absence, disease will develop.

2.2 Discovery of Vitamins

The first vitamin was discovered in 1897 by a Dutch biologist named Eijkman. He found that when bran was removed from rice, people consuming the refined rice developed beriberi, a serious disease. Eijkman also observed that when people ate the rice with the bran intact, no beriberi resulted. This finding directed Eijkman and other scientists to chemically analyze rice for the substance which, when not present in adequate amounts, resulted in the development of beriberi. Thiamine, named vitamin B1, was discovered to be this mystery substance.

In the following years, scientists found that there are many chemicals in food which are necessary for maintenance of health. One by one, as they were discovered, names were given to these chemicals As a group, they were named "vitamins."

2.3 Sources of Vitamins

It is crucial to understand that scientists have not isolated every substance in food that is essential for normal functioning of the body. Thus, we must depend on food, not vitamin pills, for good nutrition. There is no vitamin pill that contains all the vitamins the body needs.

2.4 Function of Vitamins

Vitamins function in the body as coenzymes. To understand this function, consider an analogy. Suppose you were trying to build a house. The size of the house is strictly limited by your budget. You begin the process by buying the major raw materials: cement, wood and outdoor siding material. Once you have laid the foundation and framed the walls, you go to the store and buy all the windows you need. The number of windows is obviously limited by the spaces you have built in the walls for windows. For proper function of the house, you need windows.

Vitamins are like the windows in the house. Your body has a need for vitamins (windows) when it is trying to manufacture something: new tissue, energy, etc. (a house). Your body determines the exact amount it wishes to produce and brings together just enough raw materials for the purpose of construction (cement, wood, etc.). The body manufactures the necessary amount of apoenzyme (window frame) to combine with the vitamin coenzyme (window) to form an active enzyme. The active enzyme then makes a chemical reaction progress quickly (it catalyzes the reaction) leading to the formation of the desired end-product.

2.5 Vitamins Are Inert

"Vitamin function" is a commonly used phrase, as is "vitamin action." Yet these expressions convey a misconception Vitamins cannot act, since they are inert chemical substances. In any and all physiological processes, it is the body that acts. Vitamins are used by the body for many purposes. Usually, vitamins combine chemically with other substances, thereby fulfilling the mandate of the body. It is crucial to remember that it is the body that acts on the vitamin, not the vitamin that acts on the body.

2.6 Vitamins Work Together and With Other Nutrients

Although this lesson discusses vitamins exclusively, it is important to realize that vitamins do not function alone or in a vacuum within the body. Vitamins work together; for instance, production of energy by the body when food is burned in the cells depends not only on vitamin B1, but also on vitamins B2 and niacin.

Furthermore, vitamins work together with all other nutrients such as fats, carbohydrates and proteins. For instance, vitamin B6 is needed for the normal metabolism of protein. So, even though this is a lesson on vitamins, don't think of vitamins alone when you consider the functioning of the body. Vitamins are only one small part of the metabolic machinery of the body.