By Michael Ormsbee, Ph.D., Florida State University

Edited by Kate Findley, The Great Courses Daily

Protein is a vital component to a balanced diet. But how do you know if you’re eating the proteins your body truly needs? Dr. Ormsbee explains how to look for quality proteins and also how vegetarians can make sure they’re not missing out on protein.

Amino Acids

Protein is packed with benefits—not only can it help you lose fat and build muscle, but it also fuels your daily activities. Similar to carbohydrates and fats, proteins contain carbon, hydrogen, and oxygen, but proteins also have nitrogen, which distinguishes them from the other macronutrients. Proteins are composed of amino acids that are linked together by peptide bonds and known as the building blocks of life.

Twenty different amino acids exist, and they can all combine to make unique cells and different proteins in our bodies. Because so many different types of foods can provide you with protein, how can you tell if a specific source of protein is a good-quality protein?

One way to tell is by knowing the biological value of the protein—the higher the biological value, the higher the quality. There are two types of proteins: essential and non-essential. 

They are either essential to include in our diets because our bodies don’t make them, or non-essential because our bodies make them from other proteins, so we don’t need to worry about eating them. There are 11 non-essential and nine essential amino acids. Not surprisingly, essential amino acids are the ones we tend to worry about most.

Complete Proteins

When proteins contain all of the essential amino acids, they are called complete proteins, and they have a high biological value. These proteins are typically from animal sources and include meat, poultry, fish, eggs, milk, and cheese.

When food does not have all of these essential amino acids, they are called incomplete proteins, and they have a low biological value. These are lower quality proteins that are missing at least one of the essential amino acids. 

A diet made up of incomplete proteins may eventually lead to protein malnutrition. Examples of incomplete proteins are usually found in plants, grains, nuts, and vegetables.

Protein for Vegetarians

Classifying the amino acids like this is probably most important for those of you who do not eat animal products. This is because animal meats contain all of the essential amino acids, but plant products generally do not.

One exception is soy. Soy is a plant product that does contain all of the essential amino acids, making it a complete protein. 

For most plant products, though, one or more of the amino acids will be missing, which could mean that you won’t be able to make certain proteins that your body needs. The good news is that most people don’t eat only one source of plant food, and by combining various types of incomplete proteins, you can make up for any amino acids that were missing in your diet. 

This is called eating complementary proteins, and the most common example of this is to eat rice and beans together. Other examples include a peanut butter sandwich, lentil veggie patties on a roll, and hummus on grainy crackers.

Therefore, although vegetarians and vegans have to work harder to incorporate complete proteins into their meals, it is definitely still possible to get their nutritional needs met.

This article was edited by Kate Findley, Writer for The Great Courses Daily.

Dr. Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his M.S. in Exercise Physiology from South Dakota State University and his Ph.D. in Bioenergetics from East Carolina University.