Mail from readers suggests it is time to review the facts on protein. Partly as a result of increased efforts to cut down on fat consumption, you have sent us a flood of questions about this very vital nutrient. Here is a short test to allow you to measure your protein know-how.
1. The basic building blocks of protein are the amino acids. Some are called ``essential,`` others ``nonessential.`` What is the difference?
2. Is it necessary to eat animal protein foods in order to get sufficient amounts of essential amino acids?
3. When you take in more protein than you need to build and repair body tissues, what happens to the rest?
4. Calorically, how does protein compare to carbohydrates, fats and alcohol?
5. The recommended dietary allowance (RDA) for protein for the average adult male is 56 grams. Which of the following meal combinations comes closest to that goal: a 4-ounce hamburger, a glass of milk and a cup of baked beans; a cup of cream of asparagus soup, a toasted cheese sandwich and a glass of milk; or a bowl (1 1/2 cups) of split-pea soup, a green salad with 1/2 cup of cottage cheese, a slice of dark bread and a cup of milk?
6. Should you be concerned about getting enough protein when following a reducing diet?
7. Do any vegetables besides dried beans contain important amounts of protein?
8. Is it necessary to eat foods providing all the essential amino acids at the same time?
9. Which part of an egg contains the protein?
10. What percentage of the day`s calories should come from protein?
Here are the answers:
1. Both types of amino acids are necessary for the body to make the proteins it needs. However, the body can build those considered
``nonessential`` out of basic materials, while those termed ``essential``
must come from the diet. The body either cannot make them, or during certain periods of life cannot make them rapidly enough.
2. No. While animal foods may contain a better balance of essential amino acids than those from plants, a variety of non-meat sources, if eaten at the same time, can provide sufficient amounts of the essential amino acids. But it is difficult to get enough of vitamin D, calcium and riboflavin without animal foods, particularly dairy products such as vitamin D fortified milk, yogurt and cheese. And animal food is necessary to provide the essential vitamin B-12.
3. The body`s need for protein on a daily basis is limited. Essential amino acids cannot be stockpiled if they are needed. As an alternative, they are dismantled and burned for energy. In other words, if not used for growth and repair, they simply contribute to the caloric pool.
4. Protein is calorically comparable to carbohydrate. That is, it contains 4 calories per gram compared to 7 per gram for alcohol and 9 per gram for fat.
5. The hamburger combination has the edge, providing 100 percent of the RDA for the day. The asparagus soup and cheese sandwich menu contributes 64 percent of the RDA, and the pea soup and cottage cheese meal 73 percent. These examples demonstrate why protein intakes nationwide are well above the RDA. For most of us, getting enough protein is not a practical concern.
6. It is highly unlikely that a well-planned reducing diet containing adequate amounts of other essential nutrients will be short on protein.
7. The amounts are variable, but they can add up, particularly among those who enjoy eating a lot of vegetables. Consider these examples: a cup of peas contains 9 grams; a cup of spinach or a stick of broccoli, 6 grams; a cup of winter squash, 3 grams; and a 5-ounce boiled potato, 2 grams. The body can use the protein in vegetables most efficiently if they are ``complemented``
with proteins from other foods which provide the amino acids in short supply. For example, the protein in the vegetables in a bowl of minestrone soup is made more useful if a small amount of parmesan cheese is sprinkled over it, or if served with a glass of milk.
8. To get maximum benefit from vegetable proteins, foods containing the missing amino acids should be taken at the same time. Thus the protein in dry cereal is more useful to the body if eaten with milk than if nibbled dry.
9. The protein in eggs is divided almost evenly between the white and the yolk, with the white having the slight edge. But the protein in egg white has the highest ``biologic value`` of all animal foods, meaning that it is the protein containing the amino acid combination which the body can use most efficiently.
10. A surprisingly low 12 to 15 percent of the day`s calories from a variety of foods should be more than enough to meet your essential amino acid needs.