Our Guide to Complete Protein Foods—and Why They Matter

We break down complete vs. incomplete proteins and what foods to eat for each.

Fact checked by Emily Peterson

Protein is a key macronutrient found in a variety of foods that provides lasting energy, fuel for tissue growth and repair, and the means for hormone and enzyme creation in our bodies (among other incredible benefits). While there are many healthy protein food sources, only some are considered complete protein foods. Here’s exactly what that means, why it matters, and how to mix and match “incomplete proteins” to get all the necessary nutrients.

What Is a Complete Protein?

Protein is made 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. The remaining nine amino acids (dubbed the "essential amino acids") cannot be created by our bodies and must be consumed. A food is considered a complete protein when it contains all nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Complete Protein Food Sources

Ideally, we should consume all nine essential amino acids daily to get the full health benefits of protein. By eating complete protein foods, you get all nine in one go. So, what to eat?

Animal-Based Complete Protein Foods

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

Plant-Based Complete Protein Foods

With the increased interest in plant-focused diets (veganism, vegetarianism, and flexitarianism) comes a renewed focus on protein—a nutrient primarily available in animal meat and products. But fully vegan, plant-based sources of complete protein do exist! And you can find them in whole sources of soy, certain whole grains, and more, like:

• tempeh

• miso

• tofu

• edamame

• quinoa

• hemp seeds

• chia seeds

• buckwheat

• amaranth

• nutritional yeast

• blue-green algae, like spirulina

Complete vs. Incomplete Proteins

While complete proteins contain all nine essential amino acids, incomplete proteins only contain a few. 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.

Some plant-based protein sources fall under the incomplete protein category. Examples include:

• nuts

• seeds

• certain whole grains (other than those listed above)

• legumes, like lentils, peas, and beans

Though they contain fewer than the nine essential amino acids, they're still excellent, nutritious foods to eat. And the good thing is that with incomplete proteins, you can layer and combine certain foods to fill in the gaps.

How to Combine Incomplete Proteins

If you typically eat a plant-based diet 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’ll get all the amino acids you need. (Most plant-based eaters follow this method and show no symptoms of protein deficiencies.) Others suggest eating complementary incomplete proteins, combining to form a complete protein within the same meal.

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 to create a complete essential amino acid profile.

Pair Whole Grains With Beans or Legumes

Pairing whole grains (rice, crackers, bread) with legumes or beans is an excellent way to combine incomplete proteins. Some tasty examples include Cuban black beans and rice, rice baked with peas, pasta or rice salad with chickpeas, and pita with homemade hummus.

Pair Whole Grains With Nuts or Seeds

Similarly, pairing whole grains with nuts and seeds will provide a complete protein source. Family favorites like a peanut butter sandwich on whole-grain bread, oatmeal topped with nut butter, energy balls with nut butter and oats, oatmeal and nut bars, and pasta with pine nuts are great options.

Pair Beans or Legumes With Nuts or Seeds

Combining beans and legumes with nuts or seeds is another wonderful way to eat complete proteins. Healthy options include a mixed bean salad with crushed walnuts, hummus topped with pepitas (pumpkin seeds), bean chili with pesto, and lentil soup sprinkled with walnuts.

How Much Protein Per Day Should We Eat?

The ideal protein intake for the average person is about 0.8 grams of protein per kilogram of body weight each day; some folks may need more depending on individual circumstances (consult a local dietitian or your doctor for specifics). While the trend of eating a high-protein diet doesn't seem to be going anywhere, on average, U.S. citizens are eating more protein than they need, so protein overloading isn't necessary. Plus, while the exact number is up for debate, we can only absorb between 25 and 40 grams of protein in one sitting, further illustrating the importance of consuming the right balance—not too much or too little.

Effects of Too Much Protein

The importance of eating a balanced diet with proportionate amounts of protein is evident when we realize that eating too much protein can have harmful effects on the body. A daily overconsumption of protein can put you at an increased risk for heart disease, kidney stones, and colon cancer (especially if your primary protein source is red meat).

When it comes to protein foods, the more we know, the better choices we can make. When understanding complete proteins vs. incomplete proteins, it’s important not to get too bogged down by 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.

Related: 40 High-Protein Dinner Recipe Ideas to Fuel Your Family

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