Our body is a biochemical factory which can make many compounds for its needs. However, there are limits to this, and what our body cannot make has to be provided by a suitable choice of food. Such compounds are called essential nutrients. Each one of the nutrients has many components. For example. most proteins are composed of twelve to twenty different amino acids. Ten of them cannot be manufactured by the body and have to be supplied through diet. They are called essential amino acids. The remaining are non- essential amino acids, in the sense that they can be made in the body from any protein food we take. Similarly, a large number of vitamins and minerals and some fatty acids cannot be made in the body. So they must be included in the diet.
Plant Proteins vs Animal Proteins
Proteins can be obtained from a variety of sources, such as grains, pulses, nuts, milk, fish, meat:eggs, etc. But the nutritive quality and digestibility of these proteins is not equal. They are present in different amounts in different food stuffs and their quality and the ease with which they can be digestedcalso differs with their so,urce. Animal proteins have all the essential amino acids and are called complete or high-quality proteins. They also have much higher digestibility. Plant proteins lack one or more essential amino acids an+re called incomplete proteins. Their digestibility is about 60%. Proteins, obtained from a variety of plant sources can together be made as good as a single animal protein, because what is missing in one plant protein may be compensated by another. For instance, in a meal of cereals and pulses plant the essential amino acids missing in cereals are found.in pulses and vice versa. Surprisingly, we Indians have been eating a combination of chapati-dal, or rice- dal over the years, probably out of wisdom or experience. without any knowledge of the existence of amino acids. Remember, a mixed diet of various cereals, millets and pulses can fulfil the total nutritional requirements of vegetarians. Soyabean is the richest source of plant protein. In comparison to other legumes, it contains twice as much protein. Eggs are relatively a cheaper source of high-quality proteins when compared to meat. In India, a large percentage of people can afford only cereals which contain mostly carbohydrates. Protein foods are expensive, thou'gh even the prices of vegetables are going up. Scientists all over the world are trying to find ways and means of obtaining proteins from new sources. Methods of extracting proteins