What’s the Difference Between Complete and Incomplete Protein?

단백질보충제 You’ve heard about protein, and that it’s essential to a healthy diet. But have you ever wondered about the difference between complete and incomplete protein?


Generally, animal foods (meat, fish, chicken, eggs, quinoa) are complete proteins, and plant foods such as beans, nuts, seeds, rice and grains are incomplete proteins. They can be combined in a meal or throughout the day to create complementary proteins.

What is an Incomplete Protein?

Proteins are biochemical compounds made of chains of amino acids that help create and repair tissues (including muscle), make enzymes, hormones and other chemicals in our bodies. Because protein is so essential, it’s important to get enough of it in our diets, especially if we want to stay healthy and build muscle. Protein is found in meat, fish, poultry, dairy products and eggs, as well as some plant foods like quinoa, soybeans and amaranth. Protein is considered complete when it contains all nine essential amino acids, which are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan and valine.

Protein is generally categorized as incomplete when it does not contain all nine essential amino acids or has them in low quantities. Foods that are incomplete include beans, certain nuts and tofu. It’s possible to combine incomplete proteins, such as peanut butter on whole wheat bread or rice and beans, to create a complete protein. This is called a complementary protein, and it helps ensure that you’re getting all the essential amino acids your body needs.

While much of the focus when it comes to protein is on the amount, it’s also important to understand that quality is just as important. That’s why it’s important to learn about complete and incomplete proteins so that you can be sure you’re incorporating the right kind into your diet.

What Are the Essential Amino Acids?단백질보충제

The amino acids that are necessary for your body to function, build muscle, and recover from exercise are known as essential amino acids. Our bodies can produce 13 of these amino acids, but must get the remaining nine from food.

Protein is made up of amino acids, and of the 20 that our bodies need, nine cannot be produced by our body and must come from food. The nine are histidine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, and valine.

Incomplete proteins lack one or more of these essential amino acids, but are still healthy for you if you’re eating them in addition to complete proteins. If you eat a variety of plant-based foods, such as legumes, lentils, nuts, seeds, and whole grains on a regular basis, you’ll likely be able to get all of the essential amino acids.

The exception to this is if you have a condition called phenylketonuria (PKU), where your body can’t convert phenylalanine to tyrosine, and you need supplemental tyrosine and other amino acids.

While spinach contains all the essential amino acids, it lacks sufficient quantities of leucine, isoleucine, and lysine to be classified as a complete protein. Legumes, such as lentils and beans, are also incomplete protein sources, but you can combine them with other foods like grains or peanut butter to make them complete proteins. Collagen is another example of an incomplete protein, but it can be fortified with tyrosine and other amino acids to make it a complete protein.

How Do I Get More Amino Acids?

Protein is a crucial component of a healthy diet. It helps build and repair tissues, including muscle, and is used to make hormones and enzymes. It is also a key building block for our hair, skin, nails and more. The body can naturally produce 11 of the 20 amino acids it needs; however, nine must be sourced from food and are considered essential.

Protein can be found in a variety of foods, including fish, poultry, meat, dairy products and eggs, as well as plant-based foods like beans, quinoa, certain nuts and seeds, and tofu. It’s important to vary your protein sources throughout the week and day to get all nine of the essential amino acids.

Many people have heard that you need to eat complementary incomplete proteins together at the same time to create a complete protein. This is a myth that dates back to a book written by Frances Moore Lappe in 1971, although she has since retracted her stance on the subject.

The bottom line is that if you eat a wide variety of plant-based proteins—like legumes, nuts and seeds, quinoa, beans, tofu, and whole grains—on a daily basis, you will likely be getting all the amino acids your body requires. As an added benefit, a diet rich in these foods may help diversify the gut microbiome.

Is It Necessary to Eat Complete Proteins?

Proteins are the shapeshifting workhorses of the body, doing everything from fending off disease as antibodies to digesting food as enzymes. But the protein we eat is only as good as its amino acid profile.

Protein-rich foods that provide complete proteins contain all nine essential amino acids in high enough quantities to support our bodies’ functions and aid in growth, muscle repair and other vital processes. Most complete proteins are animal-based, including meats, fish, poultry, eggs, dairy and cheese. However, some plant sources of complete protein are also healthy options: quinoa, beans and nuts.

While spinach does contain all nine essential amino acids, it lacks sufficient quantities of one particular amino acid to be considered a complete protein, which is why it is often categorized as an incomplete protein. Other examples of incomplete proteins include peanut butter, a vegetable such as peas and many whole grains including brown rice, whole wheat couscous or freekeh.

To get the most out of your protein, it’s important to eat a wide variety of foods that contain complete proteins as well as incomplete ones. By mixing and matching incomplete proteins — for example, pairing a grain low in methionine (like buckwheat or amaranth) with legumes high in lysine (like peas or peanuts) — you can make your meals into complete protein sources.