Protein is a nutrient found in every cell in your body. Your body must have protein to function properly. Sources of protein include various animal and plant foods, but some animal sources are high in saturated fat. A healthy diet includes protein-rich, low-fat foods that contain fiber, vitamins and minerals.
Function
Protein is a key component of your skin, organs, muscles and glands. Your body uses protein from foods you eat to help repair cells and produce new ones. Protein also plays an important role in the growth and development of children, adolescents and pregnant women.
Features
Twenty different amino acids join together to make proteins. Your body makes some of these amino acids, but the rest you must get from your diet. Those that must come from foods you eat are essential amino acids. Dietary sources of protein are classified according to how many essential amino acids they contain.
Types
A complete protein source, according to the Centers for Disease Control and Prevention, or CDC, "is one that provides all of the essential amino acids." Another name for a complete protein source is high quality protein. Incomplete protein sources are those that are low in at least one of the essential amino acids. Two or more incomplete protein sources that together provide all the essential amino acids are complementary proteins.
Sources
Good dietary sources of protein include meats, fish, poultry, eggs, tofu and dry beans and peas. Others are milk and milk products, seeds and nuts, grains and some fruits and vegetables. Animal-based foods are complete protein sources, but they are also often high in fat and calories. According to MedlinePlus, a service of the National Institutes of Health, the only plant food that is a complete protein source is soybeans.
Considerations
The CDC recommends that 10 to 35 percent of your daily calories come from protein. The Recommended Dietary Allowance for women 19 to 70 years of age is 46 g, and for men of the same age group, 56 g. The RDA for children 9 to 13 years of age is 34 g, and for children 4 to 8 years of age, 19 g. Girls 14 to 18 years of age need 46 g of protein daily, and boys of the same age group need 52 g.
Most Americans get all the protein they need from a normal diet. For example, a 3-oz. serving of meat contains approximately 21 g of protein, a cup of milk has 8 g, and 1 cup of dry beans contains about 16 g, according to data from the CDC.
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