Similarly to many (most?) adults, fetuses find the taste of kale so repulsive that it makes them twist their faces in disgust while in the womb, according to a new imaging study. Interestingly, the taste of carrots makes them smile.
In a recent experiment, researchers at Durham University’s Fetal and Neonatal Research Lab, UK, took 4D ultrasound scans of 100 pregnant women to observe the reactions of 100 fetuses to the foods eaten by their mothers, and found that they respond favorably to carrot but dislike leafy greens. This is the first direct evidence that babies react differently to various smells and flavors while in the womb.
“A number of studies have suggested that babies can taste and smell in the womb, but they are based on post-birth outcomes while our study is the first to see these reactions prior to birth,” study author Beyza Ustun explained in a statement.
The researchers looked at how the fetuses react to different foods by giving capsules containing either carrot or kale powder to pregnant women at both 32 and 36 weeks of gestation. Scans conducted shortly after ingestion revealed that fetuses exposed to carrot showed more of a “laughter-face” while those exposed to kale displayed more “cry-face” responses.
“This effect occurs within a relatively short time: Around 30 min after maternal ingestion of the flavor capsules, we detected observable facial reactions in the fetuses,” the study authors write. “Thus, in this short time, the flavor content of the capsules undergoes digestion, absorption into the mothers’ bloodstream, metabolization and circulation through the placenta and fetus, collection in the amniotic fluid, and fetal chemoreceptors.”
According to the research team, the disgusted faces elicited by kale tend to develop later during pregnancy than the delighted carrot faces, which is due to the fact that looks of disgust require more complex facial muscle contortions than contented expressions.
The study, which was published in the journal Psychological Science, may help to shed light on the development of human taste and smell receptors, and could facilitate the development of healthy eating habits by familiarizing babies with certain foods before birth.
“It could be argued that repeated prenatal flavor exposures may lead to preferences for those flavors experienced postnatally,” said study author Jackie Blissett. “In other words, exposing the fetus to less ‘liked’ flavors, such as kale, might mean they get used to those flavors in utero.”
“As a result, we think that this repeated exposure to flavors before birth could help to establish food preferences post-birth, which could be important when thinking about messaging around healthy eating and the potential for avoiding ‘food-fussiness’ when weaning.”
In other words, children could be made to like healthy foods before birth – a feat that is, as all parents know, really difficult to accomplish postpartum.
“The next step is to examine whether fetuses show less ‘negative’ responses to these flavors over time, resulting in greater acceptance of those flavors when babies first taste them outside of the womb.”
Hence, the team is now conducting follow-up research to find out how this experiment has affected the food preferences of the babies involved after they were born.
Sources: 1, 2, 3