Osborne a few years ago conducted experiments which demonstrated that something more than pure food elements and salts is essential for growth and development. They found that rats fed on starch and fat lived only four to eight weeks. When protein was added they sometimes lived and grew and sometimes remained stunted or died. It was thus evident that proteins differ. Their observations proved very clearly that there are perfect and imperfect proteins. The protein of corn, zein, for example, was shown to be incapable of supporting life. With the addition of a chemical fraction, tryptophan, obtained from another protein, the rats lived, but did not grow. By adding another fractional protein, lysin, the rats were made to thrive.
A minute study of the subject by Osborne, Mendel and numerous other physiologic chemists have shown that a perfect protein is composed of more than a dozen different bodies called amino-acids, each of which must be present in the right proportion to enable the body to use the protein in body building. Each plant produces its one peculiar kind of protein. The protein of milk, caseine, is a perfect protein. Eggs and meat, of course, supply complete proteins, but among plants there are many imperfect proteins.
McCollum has demonstrated that grains, either singly or in combination will not maintain life and growth. The same is true of a mixture of grains with peas or navy beans. Another element is lacking which must be supplied to support life and growth.
With these facts before us we are prepared to inquire what place in the dietary are nuts prepared to fill? With few exceptions nuts contain little carbohydrate (starch or sugar). They are, however, rich in fat and protein. On account of their high fat content they are the most highly concentrated of all natural foods. A pound of nuts contains on an average more than 3,000 calories or food units, double the amount supplied by grains, four times as much as average meats and ten times as much as average fruits or vegetables.
For example, according to Jaffi's table, ten of our common nuts contain on an average 20.7 per cent. of protein, 53 per cent. of fat and 18 per cent. of carbohydrate, as shown in the following table: