Amino acids are the building blocks of proteins that your body needs to construct and replenish tissue, red blood cells, and enzymes. Of some twenty required amino acids, your body can manufacture all but eight of them. These select eight are called essential amino acids. Proteins in meat have all eight essential amino acids and thus are referred to as complete protein. Vegetables, with the notable exception of soybeans, do not possess all the essential amino acids, and therefore their proteins are termed incomplete.
People who, for economic or personal reasons, eat scant quantities of meat, eggs, and dairy products and large portions of whole cereal grains are nutritionally safe, too, because animal protein has a surplus of the essential amino acids that cereal grains lack. This pairing partially explains why millions of people in southern China can remain healthy on diet consisting of a high proportion of rice (which, like cereal grains, is particularly low in the amino acid lysine) while usually eating no more than a meager serving of seafood (high in lysine).
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