How To Get Good Protein
Most animal proteins, including meats, fish, poultry, dairy products, and eggs, contain reasonable amounts of all the essential amino acids plus a healthy supply of the nonessential ones. They are therefore called complete proteins. By themselves, they provide balanced protein which the body can use to meet its own protein needs. An exception among animal-derived proteins is gelatin. Gelatin is missing two essential amino acids, tryptophan and lysine. Thus, if you eat a gelatin dessert by itself as a snack, your body derives no useful protein.
In addition, certain animal proteins contain less than an ideal amount of one or another essential amino acid, and, by themselves, they cannot support continued growth. These are called partially complete proteins: among them, the protein in some fish, which has relatively little methionine, and the milk protein casein, which is short on arginine that is essential during infancy.
Proteins from vegetable sources are even more incomplete. They contain small amounts of one or another essential amino acid, most commonly lysine, methionine, or tryptophan. If a particular vegetable protein is eaten by itself, your body cannot take full advantage of it as a protein source. Only part of the vegetable’s total protein can be used as protein. However, by eating two or more vegetable proteins that make up for each other’s deficiencies, you can, in effect, create a complete protein for your body to use. Such combinations are called complementary proteins.
For example, if you eat a food made from corn, which is low in the essential amino acids tryptophan and lysine, together with beans, which are low in methionine but have plenty of lysine and enough tryptophan, you end up with as complete a protein as is found in a piece of steak. Or, if you smear peanut butter, which is low in methionine, on a piece of wheat bread, which has plenty of methionine but little lysine and isoleucine, you again have a complete protein. A sandwich made with two tablespoons of peanut butter supplies more than a third of the recommended daily protein intake for a 60-pound child.
Another way to take full advantage of vegetable proteins is to eat them with a small amount of an animal protein. Complete or partially complete animal proteins can be eaten merely as condiments to round out the protein in the vegetables that are the main part of your meal. This is, in fact, how most of the world gets its protein. In China and Japan, rice, an important source of protein-albeit an incomplete one -is usually served with a protein-containing food derived from soybeans, such as bean curd (tofu), to form complete protein. In India, lentils are the complement. In addition, very small amounts of meat, fish, poultry, or eggs are usually included in the meal. This is why a Chinese meal for four or six can be made from only half a pound of meat and provide adequate protein for all. Oriental-style cooking is a fine budget stretcher and a healthy way to eat since it contains very little saturated fat and cholesterol, both of which promote the development of heart disease.
Western examples of completed protein are a little milk on gelatin dessert, some grated cheese on a mound of spaghetti, or spaghetti with sauce that contains clams or ground beef. Other combinations that complete the protein from vegetable sources include cereal and milk, macaroni and cheese, the rice and milk in rice pudding, a noodle casserole with tuna. You can greatly increase the protein value of baked goods by adding skim milk. Two tablespoons of dried milk powder for each cup of wheat or rye flour increases the protein value of the bread by about 45 percent.