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CANCER AND NUTRITION: PROTEINS
Proteins are extremely important. Every cell in the body is partly composed of proteins. Each cell is constantly exposed to wear and tear and eventually dies, only to be replaced by another cell. Proteins contribute about 10 to 15 percent of our total energy needs. Enzymes, which are proteins, help most of the body's chemical reactions to proceed quickly. Some very important hormones that are made in the body are proteins as well. In addition, the transport system of the blood is composed of proteins that act as vehicles to carry necessary substances to all parts of the body. Therefore, a constant supply of proteins is required so that the body can build tissues and function properly. Our only source of proteins is the food we eat. Proteins are complex structures consisting of amino acids, some of which cannot be made by the body at all and therefore must be supplied exclusively by the diet. (These include valine, leucine, isoleucine, threonine, lysine, phenyl alanine, tryptophan, methionine, and histidine.) When proteins are eaten, they are broken down into amino acids in the stomach by digesting enzymes and then used by the body to build whatever proteins are needed.
Children and adolescents tend to need more protein than adults, but the amount required varies from one individual to another. A person suffering from burns, bedsores, or other open wounds loses a great deal of protein from these sites. This loss has a deleterious effect because protein is needed to heal wounds in addition to its other functions. An active athlete needs slightly more protein per day than a normally active person because he loses protein through his sweat glands. A pregnant woman also requires more protein than a nonpregnant woman.
A healthy man weighing 140 pounds requires about 28 grams of protein per day, equivalent to about 100 to 115 calories. The source of protein does not have to be animal meat, a fact that is aptly demonstrated by pure vegetarians who are active and have normal life spans. Seventh-Day Adventists, a religious group composed of many pure vegetarians, have a very low incidence of cancer and heart disease compared with nonvegetarians.
Some sources of proteins are much better than others. Foods high in fiber, like rice, provide less energy; they are mostly bulk. Fish, on the other hand, has a higher percentage of usable energy.
Protein Deficiency. Kwashiorkor, an example of extreme protein deficiency that occurs in 1- to 3-year-old children, was first described by C. Williams in West Africa in 1933. The patient is weak, is emotionally upset, and has no appetite; growth is retarded; and there is considerable swelling all over the body. Victims also frequently have vitamin deficiencies and anemia. Another syndrome, called nutritional marasmus, results from a very low intake of all nutrients, including protein. This disorder commonly affects infants during their first year of life and is comparable to starvation in adults.
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Cancer