11 Protein
Protein is one of the macronutrients that does not show the %DV on the food labels because most people get their daily value in their diet. It is, however, valuable to know how much protein consumption is needed on an individual level.
The required daily protein intake is estimated at 50 g to 145 g daily based on the total body weight, or 0.8 g for each kg of body weight. For instance, a person weighing 56.8 kg (125 lb.) would require approximately 45 g of protein per day (56.8 kg x 0.8 = 45.44 g). The range is wide because people who take part in competitive sports or exercise strenuously require more protein than those who are less active.
Proteins are made up of long chains of compounds called amino acids. When proteins are eaten, they cannot be digested and carried into the bloodstream in their original molecular form. During digestion, a protein is broken down into amino acids that can pass into the bloodstream and travel to tissues and cells throughout the body. The amino acids recombine within the cells. The proteins can then form cell structures, enzymes, and hormones. They also repair body injury and supply the building blocks for growth. There are about 20 amino acids found in either of the two types of protein: complete and incomplete. Complete proteins contain nine amino acids (so-called “essential” amino acids) that the body cannot produce by itself. Complete proteins often contain other amino acids in addition to the essential ones. Proteins that do not contain all the essential amino acids are called incomplete proteins.
Meat, fish, dairy products, and eggs contain all the essential amino acids and so are complete proteins. Unfortunately, these complete sources of essential amino acids also contain large amounts of saturated fats. No single vegetable or plant food contains all the essential amino acids. However, as vegetarians (people whose diet does not include meat, poultry, and fish products) know, by combining two or more incomplete proteins, you can produce complete protein vegetarian dishes that contain all the essential amino acids. For example, a mixture of rice and black beans (a staple in many Latin American diets) produces the same quality complete protein as any meat dish. Other plant food combinations that supply complete protein are the following:
- Legumes combined with grains often produce a complete protein. That is, if beans, lentils, peas, or soybeans are combined with rice, wheat, or corn, all the essential amino acids will be present in the product. The same applies to menu items like lentil soup served with whole wheat bread or rice crackers, baked beans with bread, beans and rice casseroles, and bean fillings in corn tortillas.
- Grains can be combined with dairy products. For example, breakfast cereals with milk, pasta with cheese sauce, corn chowder, grilled cheese sandwiches, and rice pudding all contain complete proteins.
- Legumes can be mixed with seeds. The Middle East dish of hummus (chick peas and sesame seeds) is an example of such a combination. A snack of raisins, peanuts, and sunflower seeds can also supply all the essential amino acids.