|Along with carbohydrates and fat, your body needs protein, a nutrient made up of essential and nonessential amino acids, for good health. Your body manufactures 13 nonessential amino acids, which aren't available from food. For the body to process protein properly, the foods that you eat must contain the nine essential amino acids that are available only from dietary sources.
How does your body use protein from food? Protein helps to maintain and replace the tissues in your body, and it’s found in almost every living cell and fluid. Your muscles, organs and many of your hormones are made up of protein, and it is also used in the manufacture of hemoglobin, the red blood cells that carry oxygen to your body. Protein is also used to manufacture antibodies that fight infection and disease and is integral to your body's blood clotting ability. Both children and adults need plenty of protein to grow and develop.
Good Sources of Protein
Good low- or nonfat sources of protein include:
- Beef, poultry, pork and lamb
- Fish and shellfish
- Dairy products, including cottage cheese, cheese, yogurt and milk
- Eggs, egg whites or egg substitutes
- Dry beans, peas, oats and legumes
- Tofu and soy products
- Nuts and seeds
Proteins are considered either complete proteins (which supply enough essential amino acids) or incomplete proteins (which lack adequate essential amino acids). Meat, eggs and dairy products are considered complete proteins, but vegetables, beans and other plant products are considered incomplete proteins. However, some incomplete proteins can be combined to create a complete protein - rice and beans, peanut butter and jelly, and corn and beans are examples of complete-protein meals.
How Much Protein Do I Need?
Your protein intake will be dependent upon your age, your medical condition, your activity level and your size. The Food Guide Pyramid recommends that for most adults, two to three servings of protein a day is adequate.
Some common serving sizes of protein include:
- 3 to 4 ounces of cooked lean meat, poultry and fish (a portion about the size of a deck of playing cards)
- 1/2 cup of cooked dry beans, lentils or legumes
- 1 egg or 2 tablespoons of peanut butter, which count as 1 ounce of lean meat
If you eat a diet low in fat, choose low-fat protein portions such as fish, shellfish, beans, egg substitutes and nonfat milk products.
The Role of Protein in Special Diets
Although many good sources of protein are found in meat or animal products, vegetarians can still consume adequate amounts of protein. Vegetarians who eat dairy products and eggs can still choose from a variety of plant and animal protein sources. Vegans who eat only plant sources of food can still rely on tofu, soy products, oats, beans, lentils and peanut butter for protein.
People who eat too much protein may be at risk for high cholesterol or gout, a joint disorder. High-protein diets, such as the Atkins Diet and Protein Power, have also been implicated in kidney problems because of the extra effort the body must expend to process large amounts of protein. High-protein diets may also be high in fat and may lead to heart disease, according to the American Heart Association.
If you are concerned that you aren't getting enough protein in your diet, consult your physician or a registered dietitian for dietary help.