Complete Your Nutrition with Incomplete Proteins

Understanding complete vs. incomplete proteins will help you make sure your body gets the right amount of this essential nutrient.

Rice and Beans

There's more to protein than eggs, beef and chicken breasts—a lot more. And believe it or not, not all of it comes from animals. Some of the tastiest and most affordable proteins are probably sitting in your pantry. Adding muscle-building proteins to your diet—without adding another bland chicken breast—is pretty easy, provided you understand a bit of basic nutrition science. And of course we're going to give it to you.

Complete vs. Incomplete Proteins

Protein is made up of amino acids, which are the key movers and shakers in the human body. They help build muscle, fight off infections, and even produce hormones (in addition to thousands of other things). Humans need around 22 amino acids. The body can produce 13 of them on its own, but the remaining nine must be found in food. This is where the concept of complete versus incomplete protein comes into play.

A complete protein supplies all nine of those essential amino acids —histidine, isoleucine, leucine, methionine, lysine, tryptophan, valine, threonine, and phenylalanine—in adequate amounts. Foods that deliver complete protein include salmon, beef and chicken—the "classic" protein sources, if you will.

An incomplete protein supplies some, but not all (or not enough) of the essential aminos. For example, rice has all nine essential amino acids, but it doesn't have enough lysine and histidine to be considered a complete protein. By pairing foods that complement each other's protein profiles, you can build a complete protein without ingesting all the aminos from the same source.

Do you have to eat complementary proteins at the same time. "No you don't," says Leslie Bonci, RD, and nutrition consultant to the Pittsburgh Pirates, Pittsburgh Penguins and Pittsburgh Steelers. "It's over the course of the entire day. The body is very good about synthesizing new protein. However, some research currently looking at keeping the body in protein synthesis mode over the course of the day [suggests the need for a complete protein] as part of every single meal."

For example, you could eat beans at breakfast and rice at lunch and still get the same protein kick, but it might not be as effective as eating them both at the same meal.

Whatever way you do it, ingest all nine essential aminos daily. Long-term deprivation (which could happen with a vegetarian or vegan diet) can lead to a host of health issues.

"There might be a degree of muscle wasting," says Bonci. "You'll be more fatigued. There might be an iron deficiency, because hemoglobin does have protein in it. You might see someone whose immune system is going downward, and they'll get sick more often. You may also see some problems with bone and joint health, because you need adequate protein for that."


If you want to drop complete protein sources from your diet, one thing to keep in mind is the volume of complementary proteins you need to eat. Bioavailability refers to the body's ability to use the protein present in food. Macronutrients in your diet affect bioavailability.

"Some [foods are] better than others, primarily because there are foods that are just protein alone, like an egg white," says Bonci. "There's nothing else in there; it's just protein. It's going to have a higher bioavailability, because there is nothing competing for absorption. If you look at some of the plant-based proteins, they're also sources of carbohydrates. It doesn't mean they're bad, it just means that they don't have the same amount of protein in that given volume."

Let's say, for argument's sake, that a 3-ounce chicken breast contains 21 grams of protein. To get that amount of protein from a plant-based source, you may have to eat a higher volume, which can lead to more calories overall if you're not careful. If you're looking to bulk up, that's ideal, but if you're trying to lose weight, tread carefully.

Okay, so what are some examples?

Here are a few options that you're probably already eating:

  • Rice and beans
  • Macaroni and cheese
  • Milk and toast
  • Corn and beans
  • Cheese and crackers
  • Cheese and tortillas
  • Cornbread and black eyed peas

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