The Vital Importance Of Proteins
( Originally Published 1916 )
Some remarkable facts have been discovered in the laboratories of Osborne and Mendel at Yale. The proteins, which comprise the greater part of the body framework, are very complex. Amino-acids, though little understood at the present time, will probably, before long, become a household term. The amino-acids are the smaller divisions, combinations of which form proteins. There are about eighteen of these which must be supplied in the diet, because they are essential to life.
If a relay race is arranged to carry a message from the Mayor of New York to the Mayor of Buffalo, none of the racers can fail to appear or give out in the contest, and the message still be delivered. So, if in one's diet any of the amino-acids is absent or too small in quantity, the work of the group cannot be carried out, and health will be impaired.
There are three important diseases which are known to be due to faulty diets. Beri-beri was at one time of more frequent occurrence than tuberculosis among the natives in the United States Army in the Philippines. It has been stamped out by the substitution of brown rice for the common or polished variety. It is interesting to note that brown rice is seldom used in this country.
Scurvy is due to a faulty diet. When occurring in infancy, it is easily cured by the addition of orange juice and unsterilized milk to the diet.
Pellagra, the disease which has recently assumed such importance in some of the Southern States, is said to be due to a diet in which certain amino-acids are lacking. Corn contains a protein called zein, in which the amino-acid called tryptophan occurs in only a small proportion. More than half the protein content of corn is zein. Life cannot be sustained without tryptophan.
It is clear that our protein foods should be of sufficient variety to insure the presence of an abundance of all the amino-acids essential to life. This is an argument in favor of whole-wheat bread and cereal foods which contain the entire grain.
Professor R. H. Chittenden, after thoroughly testing out the protein element in the diets of himself and some of his co-workers, as well as of soldiers and athletes, came to the conclusion that we can live on about 50 grams of proteins daily, i. e., one-third of a gram for every pound of body weight. This is contrary to previously held opinion on the subject, the standard adopted some time ago by Voit and since quite generally followed being over twice this amount. It seems undesirable to constantly flood the system with excessive amounts of protein, because they are not completely oxidized in the body, and before excreted therefrom may either develop poisonous by-products, or at least increase the work of the kidneys to a considerable extent. The constant dripping of water from a height will eventually wear away the hardest stone. The steady over-working of the kidneys will some day cause them to weaken. On the other hand, the diet cannot be lacking in any of the essential amino-acids. It may be safer to provide 75 grams of proteins daily until we are more familiar with the amino-acid content of our foods. This is a sort of golden mean in proteid diet.
The determination of the amount of minerals required daily is not so easy. It is probable, however, that if there is variety in the diet, and the whole grain products are used, there will be no lack of minerals in the day's nutriment. Methods have not been devised for working out accurately the quantities of each of these elements needed daily, and the proportions absorbed from that which is taken in the food.