Nutrients are the individual substances that combine to make foods and to supply us with all we need to move, to grow, to live. They are usually grouped in five categories: proteins, carbohydrates, fats, vitamins, and minerals. Another substance important to nutrition is water.

PROTEIN
Proteins are the body builders and body maintainers. They help develop muscles and-create a feeling of fitness. In addition, proteins help make hemoglobin, the blood protein that delivers oxygen to and removes carbon dioxide from cells. Proteins are part of hormones (which regulate growth and body functions), of enzymes (which produce chemical changes in the body),and of genes (which determine the development of hereditary characteristics). Proteins help form anti bodies to fight infections, and they are an energy source.

Amino acids, twenty-two of them, are the building blocks of protein. Eight of them must be obtained from food eaten daily.

Proteins are called high-quality (adequate) if they supply all the eight essential amino acids in proper amounts. Beef, lamb, pork, poultry, fish, shellfish, eggs, and milk are high-quality sources.

A low-quality protein has too little of some of the eight essential amino acids. These include vegetables such as lentils and the legumes. Vegetable protein sources are called meat substitutes. Cereal grains, some fruits, and several other vegetables also contain some protein. They are usually cheap, plentiful, and filling.

Many vegetarians manage their protein needs by carefully balancing vegetable proteins with each other to provide the eight amino acids in proper amounts. Most people, however, opt for the simple protein insurance policy of eating both vegetable and animal proteins.

Because our bodies cannot store amino acids, we need small amounts of protein daily, preferably at each meal. Nutritionists recommend that protein comprise about 15 percent of a day’s calorie intake, or one gram of protein for each kilogram of body weight (0.424 grams per pound of body weight). This is forty-six grams for the average woman and fifty-six for the average man. Most adults in the United States regularly consume eighty to ninety grams per day. The extra protein is simply used for energy.

One typical diet mistake is that we often ignore the calorie cost of high-protein foods, erroneously assuming that protein is “thinning.” Six ounces of sirloin steak will indeed give you forty grams of protein, at a cost of 660 calories. Planning, selection, and moderation are all important when it comes to putting protein in your meals.

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