Gut: The Inside Story of Our Body's Most Under-Rated Organ

by Giulia Enders

Plants construct different proteins than animals do, and they often use so little of a given amino acid that the proteins they produce are known as ‘incomplete’. When our body tries to use these to make the amino acids it needs, it can continue to build the chain only until one of the amino acids runs out. Half-finished proteins are then simply broken down again, and we excrete the tiny acids in our urine, or recycle them in our bodies. Beans lack the amino acid methionine; rice and wheat (and its derivative meat substitute, seitan) lack lysine; and maize, in fact, is deficient in two amino acids: lysine and tryptophan. But this does not spell the final triumph of the meat-eaters over meat-avoiders: vegetarians and vegans simply have to make sure they eat a varied diet.