A complete protein is one source that provides all of the nine essential amino acids in adequate amounts. Animal products such as, meat, fish, dairy, and poultry, are examples of complete proteins. Plant foods, especially grains and legumes, often lack one or more of the essential amino acids, but become complete protein sources when they are combined. For example, combining grains with legumes results in a complete protein as the two protein sources complement each other in their amino acid profiles.
With a varied diet of grains, legumes, fruits, and vegetables, a person assured of complete proteins, as long as the calorie content of the diet is high enough. Nonetheless, when electing to eat less animal food in the diet, it is important to design the diet to provide adequate amounts of protein.