Early flavor learning and its impact on later feeding behavior.

In this review, we first outline the role and mechanisms of the chemical senses (taste, smell, and chemical irritation) in the perception of the flavor of a food or beverage. We then describe research findings, much of them from our laboratories, on the ontogeny of flavor perception and the interacting roles of innate responses and learning in the establishment of flavor preference of infants and children. Broadly, taste (sweet, sour, salty, bitter, umami, or savory) preferences have a strong innate component. Sweet, umami, and salty substances are innately preferred, whereas bitter and many sour substances are innately rejected. Nevertheless, these innate tendencies can be modified by pre- and postnatal experiences. Volatile components of flavor, detected by the olfactory system, are strongly influenced by early exposure and learning beginning in utero and continuing during early milk (breast milk or formula) feedings. These experiences set the stage for later food choices and are important in establishing life-long food habits. As many of the diseases plaguing developed and developing societies involve excess consumption of some foods, an understanding of factors that determine choice and ingestion, particularly an understanding of the early factors, is important in designing strategies to enhance the health of the infant, child, and adult.