 First, such foods do not need to be combined within a single meal.Second, though historically protein combining was promoted as a method of compensating for supposed deficiencies in vegetables as foods, studies on essential amino acid contents in plant proteins have shown that vegetarians and vegans typically do not actually need to complement plant proteins in each meal to reach the desired level of essential amino acids as long as their diets are varied and caloric requirements are met.The American Dietetic Association and Dietitians of Canada support this position.