You need protein for the repair and growth of the body. Protein is composed of chains of amino acids. There are only twenty common amino acids but they are combined in nature in an infinite number of ways so that proteins differ in structure and in their enzymatic qualities.

In the old days scientists spoke of first and second class proteins. Today we know that out of the twenty amino acids, eight are essential in that the adult cannot make them in the body, and the rest are called nonessential because they can be made from the essential ones.

One more amino acid, histidine, is needed for growing infants, and so is essential to begin with, but not later on. It is a mistake to think of the non-essential amino acids as being without value, for they too are found in the cells of our bodies; it is only that we can do without them if we have to. The essential amino acids are: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Most vegetable sources of protein are lacking in one or other of the essential amino acids, but eggs, milk, meat and fish contain all the amino acids in the correct proportions. However if you mix grains, seeds, pulses, nuts and legumes so that your diet is not consisting of a single type of vegetable protein, then the biological value of the mixture is excellent.

Indeed such a diet is good because if does not contain the saturated fat commonly present in meat.The body does not need a great deal of protein, provided this supplies the essential amino acids in the right mixture. The unwanted amino acids are converted into heat and energy and not materials for the growth and repair of the cells.

Only recently did the World Health Organization realize that vast sums were being spent on giving too much protein to the starving and under-privileged millions, when all the poor were doing was to convert the excess protein to much-needed energy. When energy providing foods are given instead the protein levels usually do not need supplementation.