Flavor experiences during formula feeding are related to preferences during childhood

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Abstract

As part of a program of research designed to investigate the long-term effects of early feeding experiences, the present study exploited the substantial flavor variation inherent in three classes of commercially available infant formulas and determined whether flavor preferences during childhood differed as a function of the class of formula (i.e., milk, soy, hydrolysate) that 4- to 5-year-old children were fed during their infancy. Age appropriate, game-like tasks that were fun for children and minimized the impact of language development were used to examine their preferences for a wide range of food-related odor qualities including infant formulas, as well as the flavor of milk-based and hydrolysate formulas and plain, sour- and bitter-flavored apple juices. Formula type influenced children's flavor preferences when tested several years after their last exposure to the formula. When compared to children who were fed milk-based formulas (n=27), children fed protein hydrolysate formulas (n=50) were more likely to prefer sour-flavored juices, as well as the odor and flavor of formulas, and less likely to make negative facial expressions during the taste tests. Those fed soy formulas (n=27) preferred the bitter-flavored apple juice. That the effects of differential formula feeding also modified children's food preferences is suggested by mothers' reports that children fed hydrolysate or soy formulas were significantly more likely to prefer broccoli than were those fed milk formulas. These data are consistent with the hypothesis that flavor experiences influence subsequent flavor preferences even several years following the early experience.

Introduction

Although there is considerable speculation that early flavor experiences influence later food and flavor preferences in humans, much of the published research, which is not extensive, fails to provide strong evidence for such effects (reviews: [1], [2]). For example, similarities in food preferences between children and their parents or siblings are often small or non-existent [3], [4], [5], [6]. However, these studies are far from definitive since developmental differences in sensory perceptive behaviors between parent and offspring could obscure similarities in response as a function of shared experience. Perhaps a comparison of parent and offspring would result in substantial similarity if individuals were to be tested when the same age. In addition, most of the studies assessed preferences for food items, rather than flavors. In the former case, differences between children and adults, independent of experiential variables, could mask effects of common early flavor experiences.

We hypothesize that if there is an effect of early experience on later preference, it would involve flavors, not specific foods since experimental animal model studies demonstrate that early experiences with odors, a major component of flavor, in specific nursing-like contexts, results in long-term preferences [7], [8], [9], [10]. Consistent with these findings, our prior research in humans has shown that, at least over the short-term, flavor experiences in amniotic fluid and mothers' milk, resulting from flavors transmitted from the mothers' diet, modify and serve to establish preferences [11], [12].

A prima facie case for the importance of early flavor experience on long-term preference can be made from observations on culture-based flavor principles. It has been said that food habits and preferences are among the last characteristic of a culture that is lost during the immigration of an individual or group into a new culture [13]. Assuming there is truth to this generalization, why has past experimental and observational research on children's food habits largely failed to find strong effects of early exposure on later preferences and acceptance? We suggest that what is missing to adequately test this hypothesis is a model system where there are profound, controlled differences in early flavor experiences. Further, a research paradigm is needed to examine the flavor components (not just the foods) of that early experience and how they impact on later flavor likes and dislikes. Finally, such research should assess children's preferences directly because the mothers' accounts of their children's preferences are often inaccurate and biased [14].

As part of a program of research designed to investigate the long-term effects of early feeding experiences, the present study exploited the substantial flavor variation inherent in three classes of commercially available infant formulas experienced by infants: traditional milk-based formulas, formulas based on soy proteins, and those based on hydrolyzed proteins [15]. Although the flavor of each brand has its own characteristic profile, milk-based formulas are often described as having low levels of sweetness and ‘sour and cereal-type’ whereas soy-based formulas are described as tasting sweeter, more sour and bitter and having a relatively strong ‘hay/beany’ odor [16]. More obvious, to adults at least, is the extremely unpalatable, offensive taste and off odor of the hydrolysate formulas due primarily to its sourness and bitterness, perhaps because many amino acids taste sour or bitter [17], and to its unique volatile profile. In the study described herein, we evaluated the responses of 4- to 5-year-old children to a range of flavor and odor stimuli as a function of their prior experiences with these classes of formulas.

Section snippets

Subjects

Mothers of healthy, 4- to 5-year-old children were recruited from advertisements in local newspapers. Three groups of children (n=102) were formed based on their early feeding history. Children in Group 1 were fed a milk-based formula exclusively during infancy (n=27), those in Group 2 were fed a soy-based formula (n=25), whereas Group 3 were fed protein hydrolysate formulas (n=50). There were no significant differences among the groups in the number of months that these children were fed

Preferences for flavored apple juices

There was no significant differences among the groups in their preference for the plain apple juice (Pearson χ2 (2df)=1.48; p=0.48). In contrast, the type of formula that children were fed as infants was related to their preferences for the sour-flavored apple juice (Pearson χ2 (2df)=6.81; p=0.03; see Table 2). Children who were fed hydrolysates were more likely to prefer the cup containing the sour-flavored juice (Pearson χ2 (1df)=6.62; p=0.01) and were less likely to make a negative facial

Discussion

The type of formula fed during infancy influenced the flavor preferences of children who were tested several years after their last exposure to formulas with distinctive flavors. Specifically, children who were fed protein hydrolysate formulas were more likely to prefer the sour-flavored juice, as well as the odor and flavor of formulas, and less likely to make negative facial expressions during the taste tests, when compared to children who were fed milk-based formulas. Those fed soy formulas

Acknowledgments

We acknowledge the expert technical assistance of Ms. Pamela Garcia-Gomez. This work was supported by Grant HD37119 from the National Institute of Child Health and Human Development.

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