PROTEINS
( Needed for
Growth and
Repair )
Proteins are vitally structural elements in all living cells. They are essential for the growth and repair of human body tissue and play an
important part in the hormone and enzyme system. There are hundreds of different kinds of proteins in your body, each carrying out certain definite tasks. They may even be used as a fuel.
Chemically, proteins are the most complicated substances known to man, with molecules consiting of thousands of atoms. They contain carbon, hydrogen, oxygen, nitrogen, and often other elements, such as sulfur, phosphorus, iron and copper.
A protein consist of a long and complicated chain of’’building blocks’’called
amino acids. Your body does not use the protein in the form in which it is eaten. It breaks the protein down to its amino-acid components and then absorbs the acids. Some kinds of amino acids can be derived from other kinds in your body. Other amino acids cannot be provided in this way; therefore they must be provided in the diet. Substances such as these are known as essential amino acids. In adult human, the essential amino acids isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine. The unessential amino acids those which ban synthesized in the body and therefore need not be included in the diet-include alanine, arginine, acid, histidine, hydroxyproline, praline, serine and tyrosine.
Proteins that contain the essential amino acids in adequate quantities are called complete, or adequate. They are found in such food as meat, milk, aggs, liver and seafoods. The proteins that do not supply the essential amino acids, or else supply in adequate amounts, are known as incomplete, or inadequate. They are usually of vegetable origin; they are provided by beans, peas, nuts, corn, cereals and various other foods.
If we eat proteins that are most like those of our own bodies-that is, animal proteins-we are most likely to meet the minimum
requirement. This does not mean that we cannot meet our
Protein needs on a strictly vegetarian diet, as the experience of many healthly vegetarians attents. However, if plants are the sole source of proteins, a greater quantity and variety of these nutrients must be eaten.
Many of us get most of our proteins from the meat of cattle, pigs and lambs. On pages 58 and 59 we show the standard cuts of beef, veal, pork and lamb. ( These are Chicago style; that is, as established in the Chicago packging houses. )
An adult should eat not less than one gram of protein per kilogram of body weight ( that is, not less than. 016 ounces per pound of body weight ) every day. In the latter part of the pregnancy period and during the period of lactation ( nursing ), larger amounts of protein should be taken. Children and adolescents should also eat larger quantities to take care of the needs for growth. The protein requirement is not changed by the amount of work done, if enough fats and carbohydrates are eaten. But if the supply of these elements is inadequate, the body will draw upon proteins for fuel and there will not be enough proteins for the building of body tissue.
In most countries people rarely suffer from protein deficiency, since their diet usually contains more protein than the minimum requirement. Protein deficiency is the cause of the disease kwashiorkor, which generally attacks young children. The first symptoms of this disease are loss of appetiteand energy. The face becomes swollen, the hair loses its color and rashes break out all over the skin : death often follows. Kwashiorkor has been overcome with protein-rich foods.
More abstracts about the PROTEINS