Plenty of Foods Have Protein, But These Foods Are ‘Complete Proteins’

Here’s what it means to eat a complete (or an incomplete) protein, according to a registered dietitian.

Protein is all the rage these days, and lately the message seems to be that we’re still not getting enough. This key macronutrient, found in a variety of foods, provides lasting energy, fuel for tissue growth and repair, and the means for hormone and enzyme creation in our bodies (among other amazing benefits). The high-protein trend has been with us for nearly a decade and doesn’t seem to be going anywhere.

But as proper protein consumption continues to rise as a nutrition priority, so too does plant-based eating. And with the increased interest in plant-focused diets, like veganism, vegetarianism, flexitarianism, comes a renewed focus on protein—a nutrient primarily available in animal meat and products. How can you up your plant intake without spoiling your required protein intake? Are you getting enough protein every day? What even is enough protein—and what high-protein foods can help you get there

That’s where the topic of complete protein comes in. While there are many healthy food sources of protein, only some of them are considered complete proteins. Here’s exactly what that means, why it matters, and how to mix and match “incomplete proteins” to get all the nutrients you need.


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Most Americans Get More Than Enough Protein

The average person needs about 0.8 grams of protein per kilogram of body weight, though some folks may need more depending on specific circumstances (consult your local dietitian for these specifics). Generally, though, Americans are actually eating more protein than they need on average, so protein overloading really isn't necessary. Plus, while the exact number is up for debate, we can only absorb somewhere between 25 and 40 grams of protein at one sitting, further illustrating the importance of consuming the right balance: not too much and not too little.

What is a complete protein?

Protein is made up of individual amino acids, the building blocks of the nutrient. There are 20 total amino acids, 11 of which the body can produce on its own. However, that leaves nine amino acids that cannot be created by the body and must be consumed. Dubbed the “essential amino acids,” these nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. 

A food is considered a complete protein when it contains all nine essential amino acids, whereas an “incomplete protein” only contains a few of them. The word “incomplete” may have a negative ring to it, but don’t worry: Foods that don’t contain all nine essential amino acids are not “bad,” “unhealthy,” or foods to avoid—these terms are simply helpful ways to classify them.

We should ideally be consuming all nine essential amino acids everyday in order to get the full benefits that protein has to offer us. So with complete protein foods, you’ll be getting all nine in one go, and with incomplete proteins you can layer and combine certain foods to fill in the gaps.

Complete Protein Foods

Now onto the good stuff: what to eat. Basically, if a protein food comes from an animal source, you can be certain it’s got all nine amino acids. Some common animal-based complete proteins include:

  • fish
  • poultry
  • eggs
  • beef
  • pork
  • dairy

But fully plant-based, vegan sources of complete protein do exist! And you can find them in whole sources of soy, certain whole grains, and more:

  • tempeh
  • miso
  • tofu
  • edamame
  • quinoa
  • hemp seeds
  • chia seeds
  • buckwheat
  • amaranth
  • nutritional yeast
  • blue-green algae like spirulina

Incomplete Protein Sources

What about all the other plant-based protein sources: nuts, seeds, certain whole grains (other than those listed above), and legumes like lentils, peas, and beans? All of these would all fall under the incomplete protein category. Again, this means they contain fewer than the nine essential amino acids—and they're still excellent, nutritious foods to eat.

How to Combine Incomplete Proteins

If you regularly consume animal-based products, you don’t need to worry much about whether or not you’re getting enough complete protein in your life. But if you typically eat plant-based or go several days without eating animal-based protein, the kind of protein you choose and whether it’s a complete or incomplete protein, is something you’ll want to keep in mind. 

Thankfully, you can combine incomplete protein sources to get all nine essential amino acids daily. There is some debate among experts over how best to accomplish this. Some say not to sweat the details, as long as you’re getting a variety of plant-based protein sources throughout your day and week, you’re going to get all the amino acids you need. While others will say that you need to eat complementary incomplete proteins, combining to form a complete protein, within the same meal.

As a dietitian, I recommend the first approach, as most plant-based eaters follow this method and show no symptoms of protein deficiencies. Also, it’s important to note that our liver stores essential amino acids, which can be combined with their complements later in the day or the week. However, those who have specific goals that hinge upon muscle mass, like bodybuilding aspirations, for instance, can certainly pair up their proteins to optimal levels.

Here are some easy and delicious ways to combine incomplete protein sources in order form to create a complete essential amino acid profile:

When it comes to protein foods, the more we know, the better choices we can make. Though, with specifics like understanding complete proteins, it’s important to not get too bogged down by the details. If you embrace variety and moderation, you can rest assured that you’re getting everything you need in a way that best serves your body.

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