Flavors from the mother's diet during pregnancy are transmitted to amniotic fluid and swallowed by the fetus. Consequently, the types of food eaten by women during pregnancy and, hence, the flavor principles of their culture may be experienced by the infants before their first exposure to solid foods. Some of these same flavors will later be experienced by infants in breast milk, a liquid that, like amniotic fluid, comprises flavors that directly reflect the foods, spices, and beverages eaten by the mother. The present study tested the hypothesis that experience with a flavor in amniotic fluid or breast milk modifies the infants' acceptance and enjoyment of similarly flavored foods at weaning.
Pregnant women who planned on breastfeeding their infants were randomly assigned to 1 of 3 groups. The women consumed either 300 mL of carrot juice or water for 4 days per week for 3 consecutive weeks during the last trimester of pregnancy and then again during the first 2 months of lactation. The mothers in 1 group drank carrot juice during pregnancy and water during lactation; mothers in a second group drank water during pregnancy and carrot juice during lactation, whereas those in the control group drank water during both pregnancy and lactation. Approximately 4 weeks after the mothers began complementing their infants' diet with cereal and before the infants had ever been fed foods or juices containing the flavor of carrots, the infants were videotaped as they fed, in counterbalanced order, cereal prepared with water during 1 test session and cereal prepared with carrot juice during another. Immediately after each session, the mothers rated their infants' enjoyment of the food on a 9-point scale.
The results demonstrated that the infants who had exposure to the flavor of carrots in either amniotic fluid or breast milk behaved differently in response to that flavor in a food base than did nonexposed control infants. Specifically, previously exposed infants exhibited fewer negative facial expressions while feeding the carrot-flavored cereal compared with the plain cereal, whereas control infants whose mothers drank water during pregnancy and lactation exhibited no such difference. Moreover, those infants who were exposed to carrots prenatally were perceived by their mothers as enjoying the carrot-flavored cereal more compared with the plain cereal. Although these same tendencies were observed for the amount of cereal consumed and the length of the feeds, these findings were not statistically significant.
Prenatal and early postnatal exposure to a flavor enhanced the infants' enjoyment of that flavor in solid foods during weaning. These very early flavor experiences may provide the foundation for cultural and ethnic differences in cuisine.
Comments
Carrot taste and baby's face: Where are the across-group comparisons?
Mennella et al.1 provided an intriguing demonstration that prenatal and early post-natal experience with carrot flavor changes the response of infants to carrot-flavored cereal compared with unflavored cereal. However, I was surprised that they did not carry out across-group comparisons on their data, contrasts that could potentially strengthen their conclusions. My curiosity led me to do the analysis. I used the proportionate response of each baby to the cereals (carrot /carrot plus unflavored), a statistic which the authors noted was particularly informative. They reported this data both in Table 2 and Figure 2, but did not analyze it. I did so using unpaired 2-tailed t-tests.
The group (CW) receiving prenatal flavor experience showed proportionately fewer negative facial expressions to carrot than the no flavor (WW) group (t(27) = 2.40, p = .02), as did the group (WC) experiencing the flavor in breast milk (t(29)= 2.37, p= .02). For mothers’ perception of the infant’s enjoyment of the feed, the prenatal group received proportionately higher enjoyment ratings than the no flavor group (t(27) = 2.13, p= .04) while the comparison between the lactation group and the control was not significant. Across-group comparisons for cereal intake or length of feeding were not significant.
Thus this analysis supports their claim that both prenatal and exposure during lactation “enhanced the infants’ enjoyment of that flavor”. Nevertheless, this claim should be accepted cautiously given that they did not report increased facial expressions of enjoyment nor find increases in intake or length of feed. Also, their design does not allow investigation of an alternative interpretation. It is possible that early exposure to a salient flavor such as carrot may predispose the infants to prefer flavored over unflavored food in general rather than to induce a specific preference for the carrot flavor experienced. Thus it would be informative to include a control group tested with a different salient flavor which the babies had not previously experienced. Overall, the research shows promise in helping us understanding how dietary preferences develop, and I look forward to further work on this topic.
Stephen L. Black, Ph.D. Department of Psychology Bishop’s University Lennoxville, QC J1M 1Z7 Canada [email protected]
REFERENCES
1. Mennella JA, Jagnow CP, Beauchamp, GK. Prenatal and
postnatal flavor learning by human infants. Pediatrics,
2001;107: E88