Animal source foods can provide a variety of micronutrients that are difficult to obtain in adequate quantities from plant source foods alone. In the 1980s, the Nutrition Collaborative Research Support Program identified six micronutrients that were particularly low in the primarily vegetarian diets of schoolchildren in rural Egypt, Kenya and Mexico: vitamin A, vitamin B-12, riboflavin, calcium, iron and zinc. Negative health outcomes associated with inadequate intake of these nutrients include anemia, poor growth, rickets, impaired cognitive performance, blindness, neuromuscular deficits and eventually, death. Animal source foods are particularly rich sources of all six of these nutrients, and relatively small amounts of these foods, added to a vegetarian diet, can substantially increase nutrient adequacy. Snacks designed for Kenyan schoolchildren provided more nutrients when animal and plant foods were combined. A snack that provided only 20% of a child's energy requirement could provide 38% of the calcium, 83% of the vitamin B-12 and 82% of the riboflavin requirements if milk was included. A similar snack that included ground beef rather than milk provided 86% of the zinc and 106% of the vitamin B-12 requirements, as well as 26% of the iron requirement. Food guides usually recommend several daily servings from animal source food groups (dairy products and meat or meat alternatives). An index that estimates nutrient adequacy based on adherence to such food guide recommendations may provide a useful method of quickly evaluating dietary quality in both developing and developed countries.