Nutrition Terms Explained- Complete Proteins

When it comes to nutrition there are plenty of terms that get thrown around that seem to be considered “common knowledge”.

During my time as a dietetic intern and then as a dietitian I have spent a lot of time talking to people of all walks of life about nutrition and I have learned that often times these terms are not terms that everyone knows and often people are afraid to ask, assuming that they should know. So, this is the first in a monthly series on “nutrition phrases explained”. Simple breakdowns of terms that get thrown around a lot!

First up “Complete Protein” this goes hand in hand with “Complementary Protein”

Legumes and Grains are complementing proteins. Together they make a complete protein
Legumes and Grains are complementing proteins. Together they make a complete protein


Let’s start with the basics- what is protein?

Protein is one of the three macronutrients (the other two are carbohydrates and fat). It provides calories and nutrients to your diet. Protein is used in the body to build muscle, tissues, even hair and nails. In the body protein is broken down into amino acids.

These amino acids are then combined in different ways and used like blocks to build hair, nails, muscle- everything that protein is responsible for. This is why amino acids are referred to as building blocks in the body.

There are around 20 different amino acids that your body uses. Your body can make most of them, however there are 9 amino acids that are considered “essential”. Essential means that your body needs them, but cannot make them and therefore they must come from food. You may hear that term with fats (essential fatty acids) or vitamins and minerals (essential vitamins and minerals), it means the same- things that the body needs, but cannot make and must get through food.

The essential amino acids are: lysine, leucine, isoleucine, valine, tryptophan, threonine, methionine, phenylalanine and histidine (histidine is only essential for children).

Complete protein sources have all nine of these amino acids. They usually come from animal sources- beef, chicken, lamb, fish, pork etc.

There are a few plant sources that offer all the amino acids- quinoa, hemp, chia and soy (including tofu, tempeh and soy beans or edamame).

However, getting adequate protein in your diet doesn’t mean you are limited to only those sources, plenty of other foods have protein as well. The problem is, they don’t have all the amino acids. For example, grains are usually low in lysine. To make a complete protein it is important to eat something else with lysine. That way you have eaten all of the essential amino acids. To do this, we complement our proteins.

Grains are usually low in lysine, but high in methionine. Legumes, on the other hand, are usually high in lysine but low in methionine. Put them together and you have a complete protein- something that contains all the essential amino acids in good ratios that are useable to the body. “Complementing” is combining foods with different amino acid profiles until you have all nine essential amino acids.


What else makes a complete protein?

Here is a quick reference for you:
Legumes (beans, lentils and peanuts), Nuts, Milk and Cheese are low in Methionine
Grains (wheat, rice, oats, rye, barley) are low in Lysine, and to a lesser extent Tryptophan, and Threonine.
Corn and Gelatin are low in Tryptophan.

Here are some combinations that complement to make a complete protein:

Legumes + Grains

Beans and Rice
Pita and Hummus
Peanut Butter (or other nut butter) on Whole Grain Bread
Falafel and Tabouleh (bulgur wheat salad)
Beans and Whole Wheat or Corn Tortillas
Black-eyed Peas and Cornbread
Indian Dal and Naan bread
Bean Salsa and Homemade Corn Chips

Dairy + Whole Grains

Oatmeal and Milk
Cheese and a Whole Wheat Tortilla
Yogurt and homemade Granola
Whole Grain Macaroni and Cheese
Yogurt and Whole Wheat Toast

Feta Cheese (dairy) and Rusks (dried bread- grains), together they are a complete protein
Feta Cheese (dairy) and Rusks (dried bread- grains), together they are a complete protein

Legumes + Seeds

Hummus (sesame seed tahini and chickpeas)

It is not necessary to complement your proteins at every meal, just make sure you do it over the course of a 24 hour period to ensure you are getting adequate protein in your diet.

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