Ultrasounds Show Fetuses Smiling In The Womb After Their Mothers Ate Carrots But Scowled Over Kale

If the taste of kale makes you screw up your face, you are not alone: researchers have observed fetuses pull a crying expression when exposed to kale in the womb. And they are a big fan of carrots, as they smiled when their mothers ate carrots.

FETAP (Fetal Taste Preferences) Study/Fetal and Neonatal Research Lab/Durham University/PA

Researchers at Durham University took 4D ultrasounds of 100 pregnant women at 32 and 36 weeks, 20 minutes after taking tablets filled with either carrot or kale powder.

They found that foetuses whose mothers had taken the carrot tablets appeared to make 'smiling faces' soon afterwards.

But scans of women who took the kale tablets showed their babies making 'crying faces'.

FETAP (Fetal Taste Preferences) Study/Fetal and Neonatal Research Lab/Durham University/PA

Comparing the two groups of women to others in a control group who hadn't taken anything indicated that exposure to just a small amount of flavour was enough to stimulate a reaction.

While previous studies have suggested our food preferences may begin before birth and can be influenced by the mother’s diet, the team says the new research is the first to look directly at the response of unborn babies to different flavours.

RESEARCHERS AT DURHAM UNIVERSITY IN NORTHEAST ENGLAND

“[Previously researchers] just looked at what happens after birth in terms of what do [offspring] prefer, but actually seeing facial expressions of the foetus when they are getting hit by the bitter or by the non-bitter taste, that is something which is completely new,” said Prof Nadja Reissland, from Durham University, co-author of the research.

Writing in the journal Psychological Science, the team noted that aromas from the mother’s diet were present in the amniotic fluid. Taste buds can detect taste-related chemicals from 14 weeks’ gestation, and odour molecules can be sensed from 24 weeks’ gestation.

RESEARCHERS AT DURHAM UNIVERSITY IN NORTHEAST ENGLAND

The team carried out a frame-by-frame analysis of the frequency of a host of different facial movements of the foetuses, including combinations that resembled laughing or crying. Overall, the researchers examined 180 scans from 99 foetuses, scanned at either 32 weeks, 36 weeks, or at both time points.

Among the results, the team found foetuses showed a crying expression about twice as often when the mother consumed a kale capsule compared with a carrot capsule or no capsule. When the mother consumed a carrot capsule however, the foetuses adopted a laughter-like expression about twice as often as they did when either a kale capsule or no capsule was swallowed by the mother.

Fetal and Neonatal Research lab, Durham University

Dr Benoist Schaal, an author of the work, from the Centre for Taste and Feeding Behaviour at the University of Burgundy, said the clarity of the results was surprising.

“[They mean] the mother has not yet finished her meal [when] the foetus is already aware, or capable of sensing, what the mother has eaten,” he said.

In designing the new study, Reissland and her team chose powdered kale and carrots over juices or raw vegetables for a few reasons. For one, powder made it easier to ensure that each participant consumed the same number of calories. (The women were also asked not to consume anything containing carrots or kale on the day of the scan.)

Reissland said the capsules were also used because some pregnant women couldn't stand the flavor of kale, and the researchers were worried that their negative reactions would influence the fetuses' responses.

"I had a number of people in the lab, and I tried to give them a kale juice to drink, and you should have seen the expressions," Reissland said.

Third, the capsules helped prevent the flavor from getting too diluted while it was being processed in the body.

"The bitter flavor gets into the small intestines and then into the mother’s blood and then into the placenta and the amniotic fluid," Reissland said. "This process seems to take around 20 minutes, and what you then get is a specific reaction of the fetuses to that flavor."

Reissland thinks her study could improve our understanding of how exposure to flavors in the womb affects eating habits later in life. If a fetus repeatedly tastes kale in the womb, for instance, that baby may be more likely to tolerate — or even enjoy — the flavor once it starts eating solid food.

Robinson said scientists have already found that exposure to different types of foods in the first few months of life "can help with willingness or acceptance of foods later in infancy."

"Diet during pregnancy is really important and influential on the health of not just the developing fetus, but the future for that child," he said.

Mothers who have healthy diets while they are pregnant may also find that their babies are less fussy eaters, Reissland said.

"If we can actually get [children] to like green vegetables and to perhaps not like sweets that much, it might help with regard to their weight gain and their weight balance," she said.