Fetuses smile at carrot taste, but grimace at kale, study suggests

() — Although it is well known that some children are not very fond of vegetables, a new study suggests that those food preferences could arise even before birth.

Fetuses create more “laugh faces” in the womb when exposed to the taste of carrots their mother consumes and create more “cry faces” when exposed to kale, also known as kale, according to a study published this Wednesday in the academic journal Psychological Science.

“We decided to do this study to understand more about fetal capacities for taste and smell in the womb,” lead researcher Beyza Ustun, a graduate researcher at the Fetal and Neonatal Research Laboratory in New York, told on Thursday by email. Durham University, in the UK.

Although some studies have suggested that babies can taste and smell in the womb through postnatal outcomes, “our research is the first to show direct evidence of fetal reactions to tastes in the womb,” Ustun added.

“The results demonstrate that fetuses in the last three months of pregnancy are mature enough to distinguish the different flavors transferred by the maternal diet.”

The study looked at the healthy fetuses of 100 women between the ages of 18 and 40 in northeast England who were between 32 and 36 weeks pregnant.

From there, 35 women were put into an experimental group that consumed an organic kale capsule, 35 were put into a group that took a carrot capsule, and 30 were put into a control group that was not exposed to any of the the two flavors.

Participants were asked not to consume any flavored foods or beverages one hour before the studies.

The mothers also did not eat or drink anything containing carrot or kale on the day of their scans to ensure it did not influence the results.

While carrot flavor may be described as “sweet” by adults, kale was chosen because it imparts more bitterness to babies than other green vegetables such as spinach, broccoli or asparagus, according to the study.

Following a 20-minute waiting period after consumption, the women underwent 4D ultrasound scans, which were compared with 2D images of the fetuses.

Twitching of the corners of the lips, suggestive of a smile or laughter, was significantly higher in the carrot group compared to the kale group and the control group. While movements such as upper lip raising, lower lip dropping, lip pressing, and a combination of these, which suggest an upset or crying face, were much more common in the kale group than in the other groups. .

“By now, we all know the importance of a (healthy) diet for children. There are many healthy vegetables, but unfortunately with a bitter taste that they do not usually like,” said Ustun. The researcher added that the study suggests that “we could change their preferences towards these foods even before they are born” by manipulating the mother’s diet during pregnancy.

A 4D scanner image of a fetus shows a smile reaction after being exposed to carrot flavor. Credit: FETAP/Fetal and Neonatal Research Laboratory/Durham University

“We know that having a healthy diet during pregnancy is crucial for children’s health. And our evidence may be helpful in understanding that adjusting maternal diet can promote healthy eating habits for children,” she added.

Improved scanning technology

Technological advances have made it possible to obtain better images of the faces of fetuses in the womb, according to Professor Nadja Reissland, director of the Fetal and Neonatal Research Laboratory at Durham University. Reissland, who oversaw the research, developed the Fetal Movement Observable System (FMOS), with which the 4D scans were encoded.

“As technology advances, ultrasounds are getting better and more accurate,” he told , adding that this “allows us to encode the facial movements of the fetus frame by frame in full detail and over time.”

The researchers have now started a follow-up study with the same babies after birth to see if the tastes they experienced in the womb affect their acceptance of different foods during infancy, according to the news release.

All the women who participated in the study were white and British.

“More research needs to be done with pregnant women who come from different cultural backgrounds,” Ustun told . “For example, I come from Turkey and in my culture we love to eat bitter foods. It would be very interesting to see how Turkish babies react to the bitter taste.”

Ustun added that “genetic differences in taste sensitivity (having a high taste sensitivity or not) could have an effect on fetal reactions to bitter and non-bitter tastes.”