[1] Food groups were a public health education concept invented to teach people eating very restricted, unvaried diets how to avoid becoming deficient in specific nutrients.
[2] Opson and sitos were Classical Greek food groups, mainly used for moral education, to teach sophrosyne.
Indian foodways had a substantial influence on European organisations such as the Vegetarian Society], which cited Indian diets as proof that a healthy vegetarian diet was possible, and were actively involved in public debate on nutrition.
In the 20th century, food groups became widely used in public health education, as a tool to reduce nutritional deficiencies.
As early as the 1980s, researchers were criticizing food groups, saying that they were a concept useful for teaching people to avoid nutritional deficiencies, but that nutritional deficiencies were no longer major cause of diet-related disease in affluent societies.