Nutrition (3) — Protein

— 3 —

Protein is a secondary source of energy, but a costly one: about one fifth of protein is consumed in generating energy. It has an important function in growth, in building and repairing the tissues, in forming the red blood corpuscles, and in maintaining life; it is likewise necessary for reproduction and nursing. Its importance is very great indeed. It is the principal element in the composition of the tissues of the muscles, the nerves, and the brain. And it is of high biological value, because it contains the complete amino acids (amino acids). Protein is broken down into these acids by the process of digestion.

These amino acids are the building blocks from which the body is built; some of them are formed in the body, and some are obtained from food that contains protein.

As for the protein of foods, it does not supply the body with all the amino acids, and they must therefore be obtained from other sources; animal protein is richer in these acids than vegetable protein.

It is worth mentioning that taking the various kinds of protein together is more useful and beneficial than taking each kind by itself. This holds true of mixing animal protein with vegetable protein, since from this mixture we obtain more of the amino acids from both sources — for example, taking cereals with meats. Meat in all its kinds — fresh meat, liver, kidney, heart — fish, eggs, milk, cheese, and all milk products, and broad beans (which count as a complete protein): all of these maintain life and promote normal growth, and they are the complete protein. Wheat, nuts, cereals, and pulses are likewise rich in protein, but it is incomplete: they are the partial protein — that is, they maintain life but do not further normal growth. The other kind of protein, which maintains neither life nor normal growth, is the deficient protein, found for example in wheat gelatin.

The amount of protein a person needs depends on the biological value of the protein consumed. It is advisable to take a sufficient quantity of it, exceeding the daily requirement, as a reserve against emergencies. The average need of the grown man is 70 grams a day, and of the grown woman 60 grams a day; and excess of food very rich in protein harms the tissues and the kidneys, and often leads to poisoning.

Deficiency of protein in the body causes effusion in the cellular tissue, a disease known as wet beriberi (Wet beriberi). Taking too little protein and vitamins, together with taking many carbohydrates, causes sores. The discussion of protein deficiency will be continued in the chapter on vitamin B.

• Protein is for growth, building the tissues, forming the red corpuscles, and maintaining life.
• The most important sources of protein: the kinds of meat, fish, eggs, milk products, and broad beans.
• The grown man's daily need of protein is seventy grams, and the grown woman's sixty grams.
• Deficiency of protein in the body causes the disease beriberi.
• Taking too little protein and vitamins, with an excess of carbohydrates, causes sores.