 Development of Food Acceptance Patterns in Early Childhood . . . page 2 Role of Genetic Factors Reaction to Flavors: Research at the Monell Chemical Senses Center (4) has shown that newborns have a positive response, as measured by facial expressions, to sweet flavors and a negative response to sour and bitter flavors; responses that may be modified by subsequent learning. The response to salty stimuli is delayed until about four months, at which time infants react positively. Mennella and Beauchamp (5) have also demonstrated that flavors such as chocolate, vanilla and alcohol in the mother's diet, reflected in the flavor of her milk, influence the sucking reflex and total breast milk intake. It is hypothesized, but as yet not tested, that these infants who have had this early flavor experience are more likely to accept the same or similar flavors in foods. They may also be more receptive to variety in flavors as other foods are introduced later. Formula-fed infants for whom there is little or no flavor variation from one feeding to the next do not have the same early experience of such a range of flavors. Neophobia: In general, young infants have a genetically related predisposition to reject new foods. This reaction is known as neophobia - fear of new. A caregiver may find this rejection inconvenient and/or interpret it as a dislike for the food offered and label the infant as a 'fussy eater'. In reality this response is entirely normal and adaptive serving to protect the child should it be offered a food which, if ingested, might lead to adverse consequences including gastrointestinal upset, nausea or even toxicity. Thus, an adult should not expect a child to accept a new food immediately unless it is sweet or salty. Instead, the caregiver should persist in offering the food repeatedly at intervals and anticipate that the child will accept it when it recognizes that the food is not associated with any unpleasant consequences. This changed behavior sometimes referred to as 'conditioned preference' or 'learned safety' may also reflect pleasant outcomes such as satiety or absence of hunger. The change is often quite dramatic but it may require three or four or as many as ten offerings before it occurs (6). Once an infant has accepted a particular food (e.g.bananas) its acceptance of similar foods (e.g. other fruits such as peaches or pears) is enhanced. The intake of other foods such as vegetables will require the usual number of trials for acceptance (7). Parents should recognize that in order to overcome neophobia the infant must consume the food not merely taste or smell it. Since omnivores need variety in their diets in order to promote adequate nutrient intake it is important that parents persist in their efforts to teach their children to accept a wide variety of flavors and textures from an early age. Environmental Factors: Positive context: Research has confirmed that feeding an infant or young child in a positive environmental context, free of distractions such as noise, activity or loss of the mother's attention is more likely to result in food acceptance than when it is offered in a negative or distracting environment. Acceptance is also more likely when the child is comfortable and hungry, but not ravenously so. Children as they experience new eating opportunities learn to associate foods with the context and consequences of eating. Although they do not need to learn to accept sweet and salty foods, their acceptance of other foods is strongly influenced by their experiences, both positive and negative, at the time they first ingest a particular food. It usually takes only one negative association to establish a 'learned food aversion' but many more to establish a 'learned preference'. For older children , coercion to eat a food with either a food or non-food reward frequently has the effect of a negative rather than a positive context. Development of Control over Total Food Intake : Fomon (9) has reported that milk consumption in very young infants is controlled by the volume of liquid, rather than its caloric density. Thus up until about six weeks of age the infant will consume the same volume of milk whether it is low fat or whole milk. After that as the infant matures, it begins to regulate intake to reflect the caloric density by drinking less of the formula of higher caloric density. Investigators (10) working with young children have shown that the ability of young children to regulate their energy intake at individual meals is erratic; there is a coefficient of variation of about 40% from meal to meal. When intake is measured over a twenty-four hour period, however, variability is reduced to 10%. In related studies, Cutting et al (11). compared the responses of daughters of mothers who imposed a high level of dietary restraint on their total food intake to daughters whose mothers had been non-restrictive. The offspring of restrictors had less ability to respond to variations in energy density when presented with foods which had varying fat and carbohydrate contents, but characteristic texture and flavor. Cutting and colleagues also showed that the response of children to a palatable food in the absence of hunger was higher in children whose intake had been controlled by maternal restriction than in children who had more freedom to control their own caloric intake. The increase in intake was higher in girls than in boys who were less often subjected to rigorous maternal control of their intake. They also showed that children learned to prefer energy dense versions of the same food and postulated that this was a reflection of the positive post-ingestive consequences of the consumption of more energy dense foods in alleviating hunger. On the basis of these and other studies on the factors involved in the development of food intake patterns in children, Birch and her coinvestigators conclude that parents who attempt to control or restrict children's eating and weight to prevent obesity may inadvertently foster the development of problems of energy balance they hoped to avoid. Similarly, child feeding strategies intended to foster an increased intake of 'healthy' foods and/or restriction or elimination of foods deemed 'unhealthy' have been shown in research situations to lead to the food behaviors they are designed to discourage, rather than to the ones they were intended to support. Children who have been denied access to 'snack-type' - foods overate them when in an unrestricted situation allowing free access to the previously-restricted food whether or not they were hungry (8). This backlash can be not only distressing to parents but also counterproductive in terms of their goals. It suggests that it may be better to promote moderation in the use of foods for which parents wish to control intake. For instance, limiting cookie intake with a glass of milk to one rather than insisting on none, or allowing one tablespoon of peanut butter on a slice of bread rather than denying the child that small amount of fat, may be an effective alternative strategy to achieve the food behavior parents wish to reinforce. Summary: On the basis of current research findings it appears that the development of each child's food acceptance patterns, genetic predisposition, neophobia, acceptance of sweet and salty flavors and the rejection of sour and bitter each interact with early experience shaped by the food environment. In general, child feeding strategies that encourage a child to consume a certain food because it is 'healthy' increases the child's dislike of that food. Conversely the rigid restriction or prohibition of intake of other foods because they are 'unhealthy' lead to over-consumption of the forbidden food whenever the child has access to it. Given a variety of foods in a non-coercive environment, a child will accept and consume a variety of foods to provide a nutritionally adequate diet capable of supporting growth and health. Children are capable of adjusting the size of meals to meet their energy needs and have demonstrated impressive ability to regulate their energy intake. For an in-depth discussion of the development of food preferences in infants and young children the reader is referred to the following review articles. Birch LL. Development of food acceptance patterns in the first year of life. Proceedings of Nutrition Society 1998; 57:617-24. Fisher JO, Birch LL. Restricting access to foods and children's eating. Appetite; 1999; 2:405-19. Birch LL, Fisher JO. Development of eating behaviors among children and adolescents. Pediatrics 1998;101:539-49 |
