Complete Proteins

To be useful to a person, the totality of food proteins must be “complete”—that is, all eight essential amino acids must be ingested simultaneously, and in the right proportion. Incomplete proteins cannot be used to build muscle and tissue; they often end up as stored fat or are utilized for energy.CD-SG 37.3

Meat is a complete protein because all eight essential amino acids are present in the proper proportion. Vegetable foods, however, may be incomplete proteins, lacking the minimum requirement of one or more of these eight amino acids.CD-SG 37.4

But it is possible to satisfy your protein needs by a proper intermixing of vegetable proteins, according to Elwood Speckmann, Ph.D., director of the nutrition research program for the National Dairy Council. “You have to be careful and make sure you use the right combinations,” explains Dr. Speckmann. “It’s simply easier to meet your protein needs with animal foods, such as meat, milk, and eggs.”CD-SG 37.5

In Diet for a Small Planet, Francis Moore Lappe offers some suggestions for combining vegetables to good advantage. Wheat, which has a deficiency in the amino acid lysine but an abundance of sulfur-containing amino acids, can be combined with beans, which have the opposite enrichment combination. Taken together, they complement each other to form a “complete” protein.CD-SG 37.6

“Certainly some vegetable proteins, if fed as the sole source of protein, are of relatively low value for promoting growth,” the editors of the British medical journal Lancet wrote in 1959. “But many field trials have shown that proteins provided by suitable mixtures of vegetable origin enable children to grow as well as children provided with milk and other animal protein.”CD-SG 37.7