The challenge of meeting nutrient needs of infants and young children during the period of complementary feeding: an evolutionary perspective

Abstract

Breast-fed infants and young children need complementary foods with a very high nutrient density (particularly for iron and zinc), especially at ages 6-12 mo. However, in low-income countries, their diet is usually dominated by cereal-based porridges with low nutrient density and poor mineral bioavailability. Complementary feeding diets typically fall short in iron and zinc and sometimes in other nutrients. These gaps in nutritional adequacy of infant diets have likely been a characteristic of human diets since the agricultural revolution ~10,000 y ago. Estimates of nutrient intakes before then, based on hypothetical diets of preagricultural humans, suggest that infants had much higher intakes of key nutrients than is true today and would have been able to meet their nutrient needs from the combination of breast milk and premasticated foods provided by their mothers. Strategies for achieving adequate nutrition for infants and young children in modern times must address the challenge of meeting nutrient needs from largely cereal-based diets.

FIGURE 1

Estimated intakes of iron (A) and zinc (B) at ages 9–11 mo. Data sources: iron content of breast milk (2), zinc content of breast milk (30), iron and zinc content of typical complementary foods (15), iron and zinc content of diverse diet with animal-source foods (17), iron and zinc content of a preagricultural diet (23). ASF, animal-source food; CF, complementary food; diverse diet with ASFs, average of diets from Bangladesh, Ethiopia, and Vietnam consisting of the country’s staple food, legumes, chicken egg, fish or chicken, and green leafy vegetables (17); preagricultural diet, average values for the nutrient content of the types of foods likely consumed by hunter-gatherers, as explained in footnotes 3 and 4 of Supplemental Table 1; RNI, recommended nutrient intake; Typical CFs, average of typical general food distribution rations provided by the World Food Program’s Emergency Operations (15).