1941: Biochemistry

Importance of Sound Nutrition.

In this abnormal period in which we live, when the energies of nations are strained to meet the requirements of implements of destruction, the problem of preserving human life and of maintaining health becomes acute. In this connection, feeding populations, and feeding them wisely, becomes more urgent than ever. In our own country we have ample food, in quantity and quality, to meet all demands. The difficulties which exist are of two kinds: the first, by far the more important, involves the limited purchasing power of a sizable portion of our population; the second, not so important, and yet a problem which cannot be neglected, deals with a lack of the knowledge we have acquired in the field of nutrition.

In the warring countries of Europe and beyond, where vast masses lack bare necessities, the situation is much more serious than in the United States. From a qualitative and biological point of view, some of the food is unwholesome; from a quantitative point of view, much of it is insufficient.

For a wholesome diet the normal adult needs from 70-80 grams (2-3 ounces) of protein per day; but some 40-50 grams of this total must be derived from 'biologically wholesome' proteins. These 'biologically wholesome' proteins are more plentiful in the animal than in the vegetable kingdom; which means that we should include in our diet one or more items such as meat, fish, milk (cheese) and eggs.

Proteins break down in the digestive tract into simpler units called 'amino acids.' These 'amino acids' are absorbed and utilized for the building and repair of body tissues. The more important ones are more apt to be found in 'animal' foods; hence the extreme importance of including them in our diet.

But the body also needs minerals (such as calcium, phosphorus and iron) and vitamins. These, under normal conditions, can be obtained from fruits and vegetables (and from the 'animal' foods already referred to). To ensure safety, a pint of milk may well be included in the daily diet.

Eating such foods as have been listed so far gives us not only proteins, minerals and vitamins, but supplies a certain amount of energy-yielding foods; the fats and carbohydrates. More of such foods can be obtained from bread (and cereals), sugar (and sweets) and butter. The daily calorific needs ('energy needs') vary considerably with different individuals. With adults, the scales serve as an excellent regulator in regard to how much energy-yielding foods are to be consumed.

Vitamins.

We have traveled very far from the single vitamin of Funk (in 1911) to the many and ever-expanding vitamins of today, almost all of which have been isolated and even synthesized.

Intensive research work is being carried on in the field of the 'vitamin B complex.' What was originally dubbed as vitamin B, or the anti-beri-beri vitamin, present in yeast, whole wheat, etc., is now but one of a number of different constituents, all belonging to the 'vitamin B complex'; such as nicotinic acid, riboflavin and pantothenic acid. It is probable that both choline and para-amino-benzoic acid will be added to this list. Choline is a nitrogenous base found in animal tissues; para-amino-benzoic acid is a well-established organic chemical, but it had not been previously identified with biological phenomena.

The sensational discovery of vitamin K, the anti-clotting vitamin, was rapidly followed by the isolation of two such vitamins, and by the synthesis of at least one of them. For much of this work we are indebted to Professor Doisy and his assistants at St. Louis University. In this connection, intensive research work is centering itself on the connection between chemical structure and physiological action, always an enticing problem. It has been shown that in the molecule of vitamin K the chemist can remove some groups without affecting the blood-clotting properties of the residue; whereas the removal (or replacement) of other groups rapidly diminishes physiological potency.

Biological Oxidation.

How foodstuffs are 'burned' or oxidized in the body at the comparatively low temperature of the body (98° F) is gradually being unraveled. There seem to be many enzymes ('oxidizing enzymes') connected with this process. A number of these enzymes have been isolated and their chemical nature determined. The most startling result so far in the course of this work has been to show that there is a direct connection between some of the vitamins and these enzymes. For example, co-carboxylase, an enzyme present, among others, in brain tissue, is nothing more than a phosphoric acid combination of vitamin B₁—the anti-beriberi or the anti-neuritic vitamin. Under normal conditions, vitamin B₁ supplies the building stones for the formation of co-carboxylase. In the absence of this vitamin, or in its presence in insufficient quantity, the formation of co-carboxylase is hindered, brain metabolism is disturbed, and nerve degeneration results.

Sulfanilamide.

Work on sulfanilamide and its various derivatives is proceeding apace. The discovery that these compounds, in varying degree, are toxic to a number of bacteria which cause various diseases, without at the same time being particularly harmful to animal tissues, even overshadows Ehrlich's pioneer work on '606' and syphilis. It is now fairly evident that one group in sulfanilamide—the so-called 'sulfonamide' group—is particularly important in influencing physiological behavior, and the various derivatives of the compound which have been prepared are based upon such experimental findings.

Structure of Proteins.

Much activity is directed in the field of proteins. While in a general way the chemical make-up of these complex and vital substances is known, the finer and more delicate structures remain a mystery. The problem before us is the following; egg albumin and casein are proteins; pepsin and insulin and virus and bacteriophage are also proteins; but how do proteins, such as egg albumin and casein, whose function is apparently served as foodstuffs, differ from a protein like pepsin, which is a digestive enzyme; or a protein like insulin, a hormone involved in carbohydrate metabolism; or proteins like the virus and the bacteriophage? The differences must involve variations in the internal structure of the molecule. But exactly what differences remains the scientist's problem.

Diabetes.

It is not so many years ago that the world was startled with the discovery by Banting and his associates of insulin, the hormone in the pancreas, now used so successfully in counteracting the effects of diabetes. It was assumed for a long time that insulin was the sole regulator of carbohydrate metabolism; and that when present in insufficient quantity those pathological symptoms associated with diabetes make their appearance. We now know that the pituitary generates one, and possibly two hormones which play as vital a part in the process as does insulin. Insulin tends to depress the amount of sugar in the blood. One of the hormones in the pituitary, the diabetogenic hormone, tends to increase the amount of such sugar. Under normal conditions, one tendency is counterbalanced by the opposing tendency, and under such conditions we find the amount of sugar (glucose) in the blood fairly constant. When, however, the islets in the pancreas which manufacture this insulin degenerate, then an excessive amount of sugar appears in the blood (and in the urine) because the diabetogenic hormone of the pituitary is no longer checked in its activity.

One of the startling results of such researches, which we owe to the Englishman Young, is that normal dogs can presumably be made permanently diabetic by excessive injections of the diabetogenic hormone. This gives us, for the first time, a clue as to the origin of diabetes.

Chemistry of the Brain.

In physiological and biochemical courses comparatively little time is devoted to the most important organ, the brain. The reason is that we know so little. For example, the brain is particularly rich in a group of compounds known as lipids, of which ordinary fat, lecithin and cholesterol are common examples; yet we are ignorant of the specific functions of these substances.

Biochemistry in America.

The Journal of Biological Chemistry is the recognized journal of biochemistry in this country. Much of the research in this field appears in this journal. But the diverse aspects of the science have forced upon contributors to publish their researches in widely scattered magazines—medical, physiological and nutritional journals, etc. Even before the present conflict the United States, together with England and Germany, led the world in the field of biochemistry. Now that the war has engulfed most of the civilized world, the better part of scientific research is done within our borders. See also BIOLOGY; CHEMISTRY.