Dietary proteins differ in their content of essential amino acids (Fig. 124-2). “Complete” proteins contain all of the essential amino acids in the right proportions necessary for protein synthesis. These proteins are found in animal products such as eggs, milk, meat, fish, and poultry. The “incomplete” proteins found in legumes, nuts, seeds, and grains provide insufficient amounts of some essential amino acids. Because the specific amino acids missing in commonly consumed plants differ, mixtures of plant proteins can be used to complement each other, which is an important consideration in the design of vegetarian diets. Common vegetarian diets include lactoovo-vegetarian (composed of milk, eggs, and plant products, and potentially deficient in iron and zinc), lacto-vegetarian (composed of milk and plant products, and also potentially deficient in iron and zinc), and total vegetarian or vegan (consisting of plant products, and potentially deficient in iron, zinc, calcium, vitamin B₁₂, riboflavin, and vitamin D). All of these vegetarian diets meet essential amino-acid requirements if a variety of plants—including grains, legumes, seeds, and nuts—are included.34,35