How Good is Our Diet? Is It Improving?

These trends in the nutrient content of the food supply from 1909 to 1945 show that the national diet has improved in nutritional quality. In fact, during the war years the levels of nearly all nutrients studied have been higher than at any time during the series. This is partly the result of relatively high purchasing power, together with large supplies of essential foods. Also, the enrichment of flour and bread has made important contributions of iron, thiamine, riboflavin, and niacin.

The quantities of the several nutrients in the wartime food supply were sufficiently high to provide every person in the country a nutritionally good diet if the nutrients had been distributed exactly in accordance with need. Unfortunately this is not the case. Dietary studies have shown that large numbers of people have less than they need of one or more nutrients. Others have liberal margins over and above what are considered adequate allowances. If diets now unsatisfactory could be brought up to recommended nutritional levels, average nutritive values for the country as a whole would need to be even higher than they now are.

The extent to which further nutritional improvement can be expected Will depend for one thing on future shifts in consumption. For example, when grain products and potatoes, good sources of several nutrients, are replaced by foods giving chiefly calories (sugars and fats), the nutritional quality of the diet is impaired. If, however, some of the calories are replaced by good nutritional investments such as milk and fruits and vegetables, there may be a net gain in the quality of the diet. Consumer demand for various foods will in turn be affected by such factors as income, relative price levels, education, and further improvements in production and marketing.

Programs for better distribution of food to low-income groups, to children, and others with special food needs offer a means of improving the national diet. Still another possibility lies in improving the nutritional quality of foods themselves, through plant breeding, and through greater conservation of naturally occurring nutrients in the utilization of foods.

THE AUTHOR

Esther F. Phipard, a food economist in the Bureau of Human Nutrition and Home Economics, has for the past 10 years been finding out about American diets what kinds and quantities of foods are consumed by different groups of families and how good their diets are nutritionally. She is coauthor of four Department bulletins reporting these studies. More recently Dr. Phipard served with a group of nutrition specialists assisting the Food and Agriculture Organization in analyzing food supply data for different countries.

Protein Is Essential to Life

by D. BREESE JONES

MORE THAN a hundred years ago a Dutch chemist named Mulder was studying the chemical composition of "silk gelatin" and egg white. He observed that they were largely composed of a material that is widely distributed in plant and animal tissues. He concluded that this substance is fundamental to all plant and animal life, and named it "protein," from the Greek word "to take the first place."

Protein is the essential constituent of all living cells. Without it life cannot exist. Most of the tissues of the body are made up largely of protein material. No other substance can take its place. The human body is about 18 percent protein.

Protein is needed to supply material for building body tissues and to furnish particular amino acids that are needed for the construction of many of the hormones and enzymes. These substances are secreted in the body in comparatively small quantities, each one performing a specific task in regulating the many physiological activities upon which life and health depend.

Pepsin, trypsin, and other enzymes that are necessary for the digestion Of food protein in the alimentary tract are of a protein nature. Insulin, a hormone secreted by the pancreas gland, controls the level of sugar in the blood. It is composed of nine amino acids. Thyroxine, an amino acid containing iodine, is secreted by the thyroid gland. A deficiency of thyroxine is associated with goiter, and retarded mental and physical development. Adrenaline, a product of the adrenal glands, profoundly affects the blood pressure. Glutathione, composed of cystine, glycine, and glutamic acid, is essential for controlling the body's chemical reactions that depend on oxidation and reduction.

The nitrogenous constituents of foods consist chiefly of protein, combined or associated with other material such as fat and carbohydrate. Protein rarely occurs in a pure or free state. Chemically, protein is one of the most complex of all organic substances. With few exceptions, proteins are composed almost entirely of the elements, carbon, hydrogen, nitrogen, oxygen, and sulfur. Some contain small quantities of phosphorus and other elements. Proteins are characterized primarily by their nitrogen content. Most proteins, particularly those of animal origin, contain about 16 percent of nitrogen, a few as high as 18 percent.

The term "protein," used as a class name to distinguish it from other substances, does not signify an individual compound. In fact, an innumerable number of proteins may contain the same elements in the same percentages and still differ radically in their chemical, physical, and physiological properties. Because of differences in the pattern of their chemical structure, some proteins and protein-like material behave as agents of destruction to health and life itself. They are generally referred to as toxalbumins; among them are ricin (the albumin of the castorbean ), the venom of certain reptiles and insects, and bacterial toxins.

Our interest in proteins increased markedly shortly before we entered the war. All of us knew there would be a much heavier demand for protein foods, particularly those of animal origin meat, milk, and eggs and that a lower production in war-devastated lands would probably cause a world shortage. The situation emphasized the need of developing as quickly as possible more information on proteins that would help meet some of the anticipated problems.