The food pyramid recommends things like 6-11 servings of grain, 2-4 of fruit, 3-5 of vegetables, 2-3 of meats/beans/nuts and another 2-3 of dairy. Is there emphasis on variety or just servings with the food pyramid? Does it matter if you get your grain and chicken from chicken breast sandwiches on wheat bread everyday or is the vitamin difference from one meat to another or one grain to another too minor to matter? What about fruits and vegetables, is variety deeply important or are the vitamins and nutrients in them similiar enough so that sticking to one or two kinds will be good enough?
At this point, we’re almost certain that variety is essential. Google on phytonutrients for more details.