Your body can make some amino acids but not others. When you eat meat and other animal products (such as milk, cheese, and yogurt), you get all the amino acids your body needs. That includes both the amino acids your body can make and those it can’t make. For this reason, protein from animals is called complete protein.
Proteins (PROH-teens) are important substances found in every cell in your body. There are many types of proteins. Some help your cells get energy from the food you eat. Other proteins build up or repair your body. Proteins also help make your bones strong and help your muscles flex. There’s even a protein inside your red blood cells that carries oxygen to every part of your body.
You can think of each protein as being like a long necklace with differently shaped beads. Each “bead” is called an amino acid (uh-MEE-noh ASS-ihd). Inside your cells, amino acids are strung together to form proteins.
When you eat foods from plants (such as beans or nuts), you’re getting incomplete protein. It’s incomplete because you’re not getting all the amino acids your body needs. But one type of plant food will have amino acids that another type of plant food is missing. So to get complete protein from plants, you need to eat a variety of plant foods. For instance, if you eat both beans and brown rice, you can get complete protein. Or you can get complete protein by eating peanut butter on whole-wheat bread.