Our bodies use 20 different amino acids to build proteins. Some amino acids can be synthesized when we need them but there are others that our body cannot make. The 9 amino acids that our bodies need but cannot make are called "essential amino acids." Foods that contain all of the essential amino acids make up "complete proteins." Most animal-based foods provide complete proteins whereas plant-based foods are not and must be eaten in combinations to get the complete set of amino acids our bodies need to function.
Nuts, legumes (including beans), seeds and whole grains all provide protein and when combined can help provide all essential amino acids. Some professionals say that quinoa is an exception as a complete, plant-based protein but others are still on the fence about this one.
By consuming a variety of foods, we can forge a picture of complete protein on our plate. Many traditional combinations from myriad cultures—rice and beans, peanuts and coconut, soybeans with sesame—are great examples of what's known as complementary proteins. Each food provides the missing essential amino acid for the other food in the complementary pair. We don't have to get all essential amino acids in one meal. Consuming complementary foods over time is sufficient to provide the amino acids our body needs.
It's not hard to come up with complementary pairings, and it's actually quite tasty. Seeds and legumes and grains and legumes make especially good protein combinations.
Take a spin around the globe to draw inspiration from traditional pairings, or come up with combinations all your own: