Learning to like vegetables during breastfeeding: a randomized clinical trial of lactating mothers and infants

Abstract

Background: What lactating mothers eat flavors breast milk and, in turn, modifies their infants' acceptance of similarly flavored foods.Objective: We sought to determine the effects of the timing and duration of eating a variety of vegetables during breastfeeding on the liking of vegetables in both members of the dyad.Design: We conducted a randomized controlled study of 97 mother-infant dyads. Lactating mothers drank vegetable, beet, celery, and carrot juices for 1 mo beginning at 0.5, 1.5, or 2.5 mo postpartum or for 3 mo beginning at 0.5 mo postpartum. The control group drank equal volumes of water and avoided drinking the juices. Mothers rated the tastes of the juices and self-reported dietary intakes at each monthly visit (0.5-4.5 mo). After weaning, when 7.9 mo of age, infants' acceptance of plain, carrot-flavor (exposed flavor), and broccoli-flavor (nonexposed flavor) cereals was assessed on separate days.Results: The timing of exposure affected the acceptance of the carrot flavor that did not generalize to the novel broccoli flavor. A relatively brief experience (1 mo) with vegetable flavors in mothers' milk, starting at 0.5 mo postpartum, was sufficient to shift the hedonic tone, which resulted in a faster rate of eating carrot-flavored cereal than that in infants who were exposed during subsequent months or not at all. One month of exposure had a greater effect than 3 mo of exposure or no exposure. Regardless of when exposure occurred, infants were less likely to display facial expressions of distaste initially when eating the carrot cereal. Over time, mothers liked the tastes of carrot, beet, and celery juices more, but no changes in dietary intake of vegetables were observed.Conclusions: Early life may be an optimum time for both infants and their mothers to learn to like the taste of healthy foods. More research is needed to facilitate the liking and eating of these foods by mothers, which will, in turn, increase the likelihood of their feeding these foods to their children. This trial was registered at clinicaltrials.gov as NCT01667549.

Keywords: breastfeeding; early exposure; flavor learning; mother-infant dyads; sensitive periods; taste; taste hedonics; vegetable intake; vegetables.

FIGURE 1

Trial design. Lactating mothers were randomly assigned to consume a variety of juices [i.e., carrot, celery, beet, and vegetable juices (colored bars)] either from 0.5 to 1.5 postpartum (1M0.5 group), from 1.5 to 2.5 mo postpartum (1M1.5 group), from 2.5 to 3.5 mo postpartum (1M2.5 group), from 0.5 to 3.5 postpartum (3M0.5), or not at all (control group). During the nonexposed months for the experimental groups or each month for the control group, mothers drank an equal volume of water (gray boxes). When infants were introduced to complementary foods (6–8 mo of age), they were videotaped as they consumed, in counterbalanced order and on separate days, cereal prepared with water, carrot juice (exposed flavor), or a broccoli juice (novel flavor). 1M0.5, exposure from 0.5 to 1.5 mo; 1M1.5, exposure from 1.5 to 2.5 mo; 1M2.5, exposure from 2.5 to 3.5 mo; 3M0.5, exposure from 0.5 to 3.5 mo.

FIGURE 2

Least-square means ± SEMs of infants’ acceptance of carrot-flavored cereal. (A) Effect of the timing of maternal drinking of vegetable juices on infants’ intake. Infants whose mothers drank a variety of juices (carrot, celery, vegetable, or beet) from 0.5 to 1.5 mo postpartum (1M0.5 group) ate more carrot-flavored cereal and ate it at a faster rate than did those whose mothers did not drink the juices and avoided vegetables (control group). There were no differences between the groups who drank the juices either from 1.5 to 2.5 mo (1M1.5 group) or from 2.5 to 3.5 mo (1M2.5 group) and the control group. (B) Effect of the duration of maternal drinking of the vegetable juices on infants’ intake. Infants whose mothers drank the juices for 1 mo (1M0.5) ate more carrot-flavored cereal than did infants in the control group but were no different from those with 3 mo of exposure. *Significant planned comparison compared with the control group. 1M0.5, exposure from 0.5 to 1.5 mo; 1M1.5, exposure from 1.5 to 2.5 mo; 1M2.5, exposure from 2.5 to 3.5 mo; 3M0.5, exposure from 0.5 to 3.5 mo.

FIGURE 3

Least-square means ± SEMs of mothers’ hedonic gLMS ratings of the taste of vegetable juices and apple juice over time. There were significant main effects for the type of juice (P < 0.00001) and time postpartum (P = 0.0005); data are collapsed across all groups. *Taste rating was significantly different from the 0.5-mo value for that juice. BD, barely detectable; CAR, carrot; CEL, celery; gLMS, general labeled magnitude scale; VEG, vegetable.