Protein is an essential substance made from building blocks called amino acids. When you eat, your body takes in certain amino acids from the protein content in your food. Food proteins that contain the full array of dietary amino acids are called complete proteins, while food proteins that contain only some of these amino acids are called incomplete proteins.
Amino Acid Basics
Your body uses 22 different amino acids to construct the proteins required to make your organs, blood, muscles and bones, according to the Nemours Foundation's KidsHealth website. Of these, 13 of these amino acids are made internally, but you must derive the remaining nine acids from foods in your diet that contain protein. Because you need these substances to survive, they are known as essential amino acids.
Complete Proteins
Complete-protein foods are also called high-quality proteins. Typically, these foods come from animal sources, and include cheese, meat, milk, eggs, fish and poultry. You may also derive complete protein from soybeans or foods made from soybeans, such as tofu and tempeh, according to MedlinePlus.
Incomplete Proteins
Incomplete-protein foods have insufficient amounts of at least one essential amino acid, according to the Centers for Disease Control and Prevention. MedlinePlus lists foods in this category that include grain, nuts, seeds, beans and peas. You can also derive complete proteins from incomplete-protein foods by eating them in certain combinations that make up for the missing amino acids in individual foods. Effective combinations of this type include rice and beans, corn and beans and wheat cereals.
Recommended Intake
If you eat meat or animal products, you will typically get enough complete protein by eating a nutritionally balanced diet, MedlinePlus reports. Vegetarians can also get adequate amounts of complete protein by eating a diet that contains a broad range of plant-based proteins. Recommended serving sizes for animal-based proteins include one egg, 1 oz of cheese or 2 to 3 oz of poultry, fish or lean meat. Recommended serving sizes for plant-based proteins include 1/2 cup of cooked dry beans or 2 tbsp. of peanut butter. Most healthy adults get enough protein in two or three daily servings from animal or plant sources. Protein recommendations for children vary considerably with age.
Considerations
While your body can use animal or plant proteins with more or less equal ease, protein-rich animal foods also often include significant amounts of potentially harmful saturated fats, notes the Harvard School of Public Health. You can reduce your saturated fat risks by emphasizing fish and poultry sources in your meat intake, or by eating only the leanest cuts of red meat. If you avoid processed meats, such as bacon and hot dogs, and keep your weekly consumption of red meat below 18 oz., you may lower your risk for colon cancer.
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