INTRODUCTION: A number of deficiency diseases plagued people, whose diets were restricted. Thus half the sailors, in the fifteenth to seventeenth century voyages, died of scurvy, due to lack of fresh vegetables and fruits in their diets. In Asia, beriberi plagued rice-cating people. Pellagra claimed many lives of corn–cating population in Southern United States in the beginning of last century.
Today we rarely see these deadly diseases in the sections of society, who have varied diets of ordinary natural foods. But in over 70 developing countries, crores of children still lose their sight due to lack of vitamin A.
It was thought that diet containing proteins, carbohydrates, fats, minerals, and water was adequate to maintain life, until the beginning of last century.
But research conducted in the early part of the last century proved that some vital factor was missing from the diet. This vital factor was given the name vitamin. Later it was found that there was more than one factor involved.
Now we know that vitamins are one of the six classes of nutrients supplied by food. They are required for normal growth and maintenance of all animal life. Vitamins are important for their regulatory and protective functions. Unlike most other nutrients they are required in very small amounts. But it is necessary to provide these in the diet because many of them cannot be manufactured by the body. The lack of vitamins results in definite deficiency disorders, which are specific for each particular vitamin.
Vitamins have captured public interest in the last sixty years. This many because they have been synthesized and marked by a large pharmaceutical industry. Their efforts have been supported by medical practitioners and health conscious public. Some people have often been misled into thinking’ if little is good, more may be better’.
Surely vitamins are essential nutrients. We need to understand what they do, how much we need them and where we can get them. Can we get enough of these in foods or do we need pills to meet our needs of some vitamins? We need sound answers to these questions.
DEFINITIONS: A substance can be classified as a vitamins if it satisfies the two criteria:
- It must be a vital, organic dietary substance, which is neither a carbohydrate, fat, protein, or mineral and necessary in only very small amounts to perform a specific metabolic function or to prevent an associated deficiency disease.
- It cannot be manufactured by the body, and, therefore, must be supplied by the diet.
NATURE OF VITAMINS: Vitamins are organic substances, which occur in small amounts in foods. They are necessary for life and growth. Chemical structure of each vitamin is specific; some like vitamin C have a simple structure, while others such as vitamin D have a complex structure.
Vitamins do not provide calories, but are essential in the metabolic reactions, which release energy from carbohydrates, fats and proteins. Vitamins are essential co-factors in hundreds of metabolic reactions in the body. They may act singly or in co-ordination with each other. Each vitamin has specific functions and so one vitamin cannot substitute for another in the body.
Vitamins are conveniently classified into two groups on the basis of their solubility into fat-soluble and water-soluble vitamins. Fat-soluble vitamins include A, D, E and K. Water-soluble vitamins include the B-group and vitamin.
Foods differ greatly in the amount and kinds of the vitamins they supply. Selection and intake of foods according the food guide can help to meet one’s need of the various vitamins.