The feeding interaction is perhaps the most important experience for infants as it supplies nutrients for growth, establishes the mother-infant bond, provides a sense of security and pleasure for the infant, and presents repeated opportunities for learning and social exchange. The newborn spends approximately 50% of its waking time in the feeding interaction; yet contemporary research regarding normal development of infant feeding behavior and maternal feeding practices is extremely limited¹.

Infants are depletion driven eaters-eating when hungry and ceasing when replete^2-4. They start life as univores,or consumers of just one food; and they are born with the necessary physiologic and developmental capabilities to ingest and digest one food-human milk or infant formula. Physiological reflexes that enable milk consumption include the rooting, suckling, and extrusor reflexes. The rooting reflex refers to nipple-seeking behavior on the part of the infant and is elicited by stroking the infant's cheek. The suckling reflex occurs when the nipple is placed in the infant's mouth. The extrusor reflex, produced by touching the infant's tongue, results in the protrusion of the tongue (underneath the nipple during a feed) so that the infant can latch onto the nipple securely. These reflexes act together and provide the physiological mechanisms that are necessary for milk consumption.

"The neonate also enters the world with specific taste preferences that complement the physical reflexes that are integral to feeding."

The neonate also enters the world with specific taste preferences that complement the physical reflexes that are integral to feeding. Human milk is a relatively sweet-tasting fluid by virtue of its high lactose content, and its sweet taste is posited to facilitate infant acceptance. Steiner documented gustofacial reflexes in newborns that demonstrate the liking for sweet taste ⁵. Further, DeSnoo ⁶ documented an increase in fetal gulp rate in response to injections of saccharin into amniotic fluid during the 3rd trimester of pregnancy, which suggests that the response to sweet taste is "hard-wired" and present even in utero. The intake-enhancing sweet-taste of human milk is thought to represent an evolutionary adaptation to support human survival. Humans also are born with an innate distaste for bitter and sour, perhaps providing further protection and survival advantage since many toxic substances are bitter ⁷.

When viewed collectively, the infant's innate reflexes, taste preferences, and the mother-infant bond established during feeding comprise a unique combination that not only makes the food intake physically possible, but also transforms eating into a pleasurable taste, emotional, and social experience.

Transition to Complementary Foods

The developmental stage and timing when children transition to solids is influenced by two major physiological events: 1) the disappearance of the extrusor reflex and 2) the continuing depletion of fetal mineral stores which are critical for the rapid, normal growth and development of infancy ⁸. Both events occur between 4-6 months and are consistent with the need to consume a more varied, adult-modified diet.

Traditionally it has been recommended that children should first be introduced to iron-fortified cereals, followed by vegetables and fruits, and meat and animal products last to avoid hypersensitivity reactions ⁹. These recommendations are currently the subject of research that may shift practice towards the introduction of micronutrient-rich foods such as meat as the first weaning foods ⁸. Micronutrients like iron and zinc are essential for appropriate growth and cognitive development. Though controversial, recommendations to introduce meat products to infants older than 6 months of age (with no family history of hypersensitivity reactions) would support the mineral requirements of the young infant and would consider a broader range of nutrients than the exclusive introduction of iron-fortified cereals.

From the standpoint of physical development, the 9-month-old rapidly continues to gain both gross and fine motor skills ¹⁰. At 9 months, the palmer grasp (gross motor whole hand grasp) and the pincer grasp (fine motor forefinger-thumb grasp) begin to emerge-aiding the infant to begin self-feeding both liquid and solid foods. In addition, by 6 to 9 months the infant can sit in an appropriate chair, unaided. These skills provide an increased means of exerting physical control over feeding and support a child's ability to self-regulate energy intake. To this end, it is important that child-feeding practices support both the acquisition of physical feeding skills as well as the child's self-regulation of food intake.

The developmental period during which the transition to solid foods is initiated is a dynamic period of growth and learning. Dietary patterns change more during this period than during any other time of life. This transition necessitates rapid learning about flavors, foods, etiquette, and social exchange. An infant's first experience with flavors may, in fact, occur before birth as flavors from a pregnant woman's diet are transmitted to amniotic fluid ¹¹. The fetus swallows fluid that likely contains these flavors, and thus the first exposure to flavors occurs in utero. Human milk also conveys flavors from the maternal diet to the breast fed infant; in contrast, the formula fed infant has a very different feeding experience with respect to exposure to flavors from food. Current findings in the area of gustatory research suggest that an infant's early experience with flavors in human milk may positively influence the transition to, and acceptance of, solid foods ^{12, 13}. Figure 1 shows that breast-fed infants consumed greater amounts of a novel food than formula-fed infants at three points during an experimental study on food acceptance during weaning. Human milk-fed infants have been noted to have a faster acceptance of the first transition foods offered and consume greater quantities of cereals prepared with human milk.

Figure 1. Comparison of breast-fed and bottle-fed infants' consumption before and after repeated experience with first solid food.

Therefore, the learning associated with repeated exposure to flavors from human milk may predispose the infant to accept solid foods more readily.

Food Neophobia-The Developmental Basis for "Picky Eating"

An often unrecognized developmental milestone in young children's eating behavior is food neophobia-literally translated as the fear of new foods. Infants and young children are predisposed to neophobia, which typically presents between 18-24 months of age. Children previously judged as "good eaters" often begin to reject new foods and exhibit refusals of formerly accepted, familiar items. This is a particularly confusing and worrisome time for parents who fear the child will suffer growth or health problems that stem from a less than balanced diet. Escalating parent-child power struggles during mealtime can perpetuate the problem. Parental confusion and anxiety engendered by children's neophobic tendencies are perhaps exacerbated by the lack of clear nutrition guidelines for this period of rapid development and growth. Nationwide survey data and longitudinal studies give credence to parental concern, indicating that the quality of food intake may be compromised during early childhood ^14-16. There is growing recognition for the construction of practice guidelines to be used by health care professionals to support parents in helping their children establish healthy eating behaviors ^{14, 17}. Children's acceptance of new foods is not instantaneous and it requires repeated exposure and experience with new foods to overcome neophobia and enhance acceptance ¹⁸. As Figure 2 indicates, research has shown that children may require 5 to 10 exposures to a new food before changes in liking are expressed ¹⁹.

Figure 2. After repeated experience with one version of a novel food, children show clear preferences for the version to which they have been repeatedly exposed over an unfamiliar version.