Complete Proteins vs. Incomplete Proteins: Everything You Need to Know

by Elena, Move to Root

Ahhhh protein. Today’s most popular macronutrient among bodybuilders, plant-eaters, and health-enthusiasts alike—and one we love to talk about, too.

As much as we would love to go into the biochemistry of all things protein (really, we would)—for the sake of time and word count, we’ve narrowed our focus for this one. Let’s clear the air on an aspect of the protein conversation that many find confusing: complete proteins.

Maybe you’ve heard that only animal products are complete protein foods or that one must ensure every meal contains the perfect combination of complementary proteins. (Both false—but we’ll get to that later.) Regardless, you’ve come to the right place! Let’s take it from the top.

What is a complete protein?

A complete protein is a food that contains an adequate amount of all nine essential amino acids.¹ Unless you’re Hank Green, this might not make total sense yet. Let’s do a quick review of protein structure.

Proteins are the shapeshifting² workhorses of the human body. From fending off disease as antibodies³ to digesting food as enzymes⁴ (that’s right, the proteins in your stomach digest the proteins you eat—so meta), there are few bodily processes in which you won’t find proteins leading the pack. So how does protein play so many roles? The answer is—can you guess it now? Amino acids.

All proteins are made up of chains of amino acids.⁵ Our bodies use a set of 20 amino acids to form any given protein chain.⁶ To illustrate how this works, think of amino acids as letters of an alphabet. Combining letters makes words, and changing the order of those letters makes new words. The same goes for amino acids in a protein chain. Rearrange or add amino acid molecules, and you’ll still have a protein—but its function in the body will be different.

Our bodies can make 11 amino acids on their own.⁶ These are referred to as nonessential. The other nine are the essential amino acids because it is essential that they are consumed through diet (pun intended)—our bodies can’t synthesize them. Now that you’ve got the basics down, reread that bolded sentence at the top of this section. We’ll wait. Are we feeling Greener?

Which foods are complete proteins?

Animal proteins (think milk, eggs, beef, etc.) are complete proteins¹, and while quality plant and fungi-based complete protein foods exist, they are not as common as you might think.

Plant-based complete protein examples⁷:

Soy
Quinoa
Chia Seeds
Buckwheat
Amaranth

In addition to plant protein foods containing all essential amino acids, there are the increasingly popular fungi-based complete proteins. Fy Protein™, for example, is a fungi-based complete protein source that contains not only all nine essential amino acids but all eleven nonessential amino acids, too. With that kind of nutritional content, not to mention the environmental benefits of fungi-based proteins, consider the “animal protein is the only quality protein” myth debunked.

Ok, what about incomplete protein foods? Are they less nutritious?

In understanding what a complete protein is, you might guess that incomplete proteins only contain a few amino acids. That isn’t necessarily true. An incomplete protein may contain all essential amino acids—just not in high enough amounts for the body to utilize alone.⁸ Examples include beans, most nuts, wheat, corn, and rice.⁹

Just because a food isn’t a complete protein doesn’t mean it’s low in protein or lacking nutritional value. For instance, most fruits and vegetables are incomplete proteins but are packed with vital micronutrients. What’s more, many whole grains don’t contain adequate amounts of essential amino acids, but consumption has been shown to have a protective effect against chronic disease.¹⁰

I’m vegetarian and have been told protein combining at each meal is crucial to staying healthy. Is this true?

For many years, it was said that plant-based eaters must combine protein sources at each meal to effectively “create their own” complete protein. When two proteins contain adequate amounts of the essential amino acids together, they’re known as complementary proteins. According to the Academy of Nutrition and Dietetics, “consuming protein from a variety of plant foods, eaten during the course of a day, supplies enough of all indispensable (essential) amino acids when caloric requirements are met.”¹¹ What does this mean? Contrary to popular belief, memorizing the essential amino acids and checking them off at each meal is unnecessary. While complementary protein foods certainly ensure adequate intake of all nine essential amino acids in one sitting, and maybe some added peace of mind, it isn’t something you need to fret about. So, unless you’re a bodybuilder (and even then), you can focus less on amino acid counts and more on consuming a variety of protein sources.¹¹

How much protein do I need overall?

Now that we’ve cleared up some of the complete protein myths, we can talk about overall protein needs. The first thing to remember is that there is no one-size-fits-all approach in any aspect of diet, including healthy protein intake. That being said, the recommended dietary allowance (RDA) of protein for an average person is 0.8 grams of protein per kilogram of body weight.¹² So, for someone weighing 140 pounds, 51 grams of protein per day should be the minimum goal. There are several instances where protein needs increase, including in times of illness¹³, pregnancy¹⁴, after age 65¹⁵, and for the highly active. If you fall into one of these categories, a registered dietitian nutritionist can be a great resource to help you understand the amount of daily protein right for you.

Choosing protein with you and planet in mind

In summary, you don’t have to worry too much about amino acid content if your protein intake is varied, and the type of protein you consume is up to you. Still, we will always encourage exploring the wonderfully diverse world of alternative proteins, one that brings us closer to a more sustainable food system for our growing planet.

Learn more about animal-free complete protein sources, like Fy, by following us on Instagram at @naturesfynd.

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1. https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/

Accessed February 2022

2. https://www.science.org/content/article/shapeshifting-proteins-assemble-and-disassemble-cue#:~:text=Proteins%20are%20master%20shapeshifters.,prone%20to%20shapeshifting%20than%20others.

Accessed February 2022

3. https://www.livescience.com/antibodies.html

Accessed February 2022

4. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/pepsin

Accessed February 2022

5. https://www.khanacademy.org/science/biology/macromolecules/proteins-and-amino-acids/a/introduction-to-proteins-and-amino-acids#:~:text=A%20single%20cell%20can%20contain,more%20chains%20of%20amino%20acids

Accessed February 2022