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How do legume crops complement the protein found in cereal grains?

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Yellow partridge pea — Fabales A flowering stalk of yellow partridge pea (*Chamaecrista fasciculata*) in the eastern United States.

Legume crops complement the protein found in cereal grains through a process known as protein complementarity, which balances the essential amino acids provided by each food source.1

Individual plant-based foods are often considered incomplete protein sources because they lack sufficient amounts of one or more essential amino acids, which are the "limiting" factors for protein synthesis in the body.1

Legumes: These are typically high in the amino acid lysine but are relatively low in methionine.1
Cereal Grains: These grains generally possess the opposite profile, offering higher levels of methionine but lower levels of lysine.1

By consuming both legumes and grains over the course of a day, their combined amino acid patterns supplement one another, providing a higher-quality protein profile that more closely meets human nutritional needs than either food could provide alone. This practice of combining plant proteins has been a vital component of traditional food patterns in many cultures worldwide.1