Healthy Eating

Complete VS Incomplete Protein: What’s The Difference?

Is all protein created equal?

By: Lauren Manaker MS, RDN, LD, CLEC

We all know protein is an important macronutrient in our diet. It helps support our body with a slew of important functions, including muscle growth, bone health, and even weight loss. And, let’s face it with endless options for protein-filled bars, powders, and snacks, there’s no protein shortage in sight. But are all protein sources created equal? Not quite! So before you decide which protein sources to include in your diet, it’s a good idea to understand the difference between complete vs incomplete protein.

RELATED: 6 Signs You’re Not Eating Enough Protein 

Complete vs Incomplete Proteins 

Complete and incomplete proteins are categorized based on their specific amino acids (the building blocks of protein). Any time you eat protein-rich food, the protein is broken down into individual amino acids and later utilized for important functions such as building and repairing muscle, supporting metabolism, and fueling other processes. 

There are 20 different types of amino acids needed to make proteins in the body. While some amino acids can be made by the body (non-essential amino acids), others (essential amino acids) must be obtained through the diet. 

But which foods provide essential and non-essential amino acids? And is one better than the other? 

Read on to learn all about complete vs. incomplete protein and how these two protein sources could affect your diet. 

What are Complete Proteins?

So, what are complete proteins? Complete proteins, also known as whole proteins, are food sources that contain all of the essential amino acids needed to make proteins. To understand this, let’s backtrack to amino acids for a moment. Of the twenty amino acids mentioned, nine cannot be produced by the body — these amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine) must come from exterior sources, such as food.

Think of it as a 20-piece puzzle. The body already contains eleven pieces (the non-essential amino acids), it just needs to find the nine missing pieces (essential amino acids) to be complete! Therefore, protein sources that contain all nine essential amino acids are considered complete proteins.

According to Harvard Health, all animal-based foods contain all nine essential amino acids and are therefore considered complete. 

Some animal-based complete proteins include: beef, poultry, fish, eggs, cheese, milk.

While most plant-based foods are incomplete proteins, some contain all nine essential amino acids and can be considered complete protein sources, too.

These plant-based foods include: quinoa, soybeans, hemp seeds. 

What are Incomplete Proteins?

When it comes to complete vs incomplete proteins, incomplete proteins lack one or more of the nine essential amino acids or contain extremely low quantities of certain essential amino acids. 

Just as animal-based proteins are most often complete protein sources, plant-based proteins are mostly incomplete proteins. With that said, incomplete plant-based proteins can combine within the body! Fear not plant-based eaters — so long as all the nine amino acids are present in a dish, you can supply your body with all the nutrients it needs to create a complete protein.

Some incomplete protein sources include: vegetables, legumes, nuts, seeds, whole grains.

How to Make Sure You Are Getting All The Amino Acids You Need

Getting all the essential amino acids in your diet is utterly important. From tissue growth to immune function to even nutrient absorption, proteins play many key roles in the body. But there is no need to log what you are eating and track every morsel in your diet in order to ensure you’re getting in all 9 essential amino acids. 

The best thing you can do to ensure you are getting all the amino acids is to eat a wide variety of nutrient-dense foods. Of course, eating complete vs incomplete protein choices will help ensure you are meeting your needs. But if you follow a plant-based lifestyle, you can still meet your essential amino acid needs by combining certain foods (sometimes referred to as protein combining) to make a complete protein choice. 

Combining grains, nuts, and/or seeds with legumes is a common protein-combining method to make a complete protein out of incomplete protein sources.

Some examples of complete plant-based protein combinations include:

  • Black beans and rice
  • Lentils and almonds
  • Whole wheat bread and walnut butter

Eating The Right Protein Sources To Meet Your Essential Amino Acid Needs

Including protein in your diet is critical to support your body’s natural functions. But eating enough protein isn’t all you need to focus on — making sure you are taking in all nine essential amino acids is key to your overall health, too! If you regularly eat foods like meat, dairy, eggs, quinoa, and soybeans, you are already taking in complete proteins, and thus, the amino acids that your body needs from your diet. But if you are following a plant-based lifestyle, combining grains, nuts, and seeds with legumes will help you meet your amino acid needs too. 

Now that you know the difference between complete vs incomplete proteins, finding ways to meet both your overall protein and amino acid needs is simple. Once you really focus on this mission, you will be able to determine which foods you need to fuel your body with in no time.