Fetuses in womb smiled after moms ate carrots, but frowned when given kale, study suggests

If you are one of those who don't particularly enjoy kale, turns out hundreds of fetuses would agree with you, a study reveals. A recent U.K. study of 100 pregnant women and their fetuses found that fetuses in the womb scowled after their moms had kale but appeared to be smiling after they consumed carrots. The study provides a unique window into how fetuses react to tastes in real time, reports NBC.

The mothers were given capsules containing powdered forms of either carrot or kale. Thirty-five women consumed capsules with one medium carrot's worth of food, while 34 women ingested the capsule that was the equivalent of 100 grams of chopped kale. The remaining 30 ladies did not eat either. Twenty minutes post the consumption, ultrasound images of their uteruses revealed that fetuses exposed to the carrot flavor looked like they were giggling, but most exposed to the kale flavor appeared to be grimacing. The fetuses in the latest study ranged in gestational age from 32 to 36 weeks. Forty weeks from the start of the last menstrual cycle is the typical length of a pregnancy. 

Nadja Reissland, a co-author of the research who heads the Fetal and Neonatal Research Lab at Durham University, explains that they're the first ones to show facial expressions of fetuses. "We are the first ones who could actually show on an ultrasound scan the facial expressions in relation to the food which the mother has just consumed," she said.

Previous studies have demonstrated that a pregnant person's diet can have an impact on the taste or fragrances of the amniotic fluid around the fetus. According to a 2001 research, children who had previously been exposed to the flavor of carrots through the amniotic fluid or breast milk reacted to carrot-flavored porridge with less unfavorable facial expressions than newborns who hadn't. However, the study only looked at the newborns' reactions outside of the womb.

Reissland explained that while the ultrasound pictures reveal reactions resembling those of children or adults who taste something unpleasant, it is unknown if fetuses genuinely feel emotions or dislikes. According to Reissland, the grimaces that appeared on the ultrasounds could just be "the muscle movements which are reacting to a bitter flavor."

She explained, however, that fetuses at this later stage have been known to make facial expressions. "If you look at it from 24 to 36 weeks’ gestation, their expressions become more and more complex," Reissland said. 

Dr. Daniel Robinson, an associate professor of neonatology at Northwestern University Feinberg School of Medicine who was not involved in the current study, advised readers not to directly read into the ultrasound pictures as they must not be interpreted as happiness or distaste. However, he pointed out that "there is the notion that newborns and infants will have a preference for sweeter flavors, and there are evolutionary ideas behind that."

Reissland believes that her research might further our knowledge of how exposure to taste during pregnancy influences eating patterns later in life. For example, if a fetus eats kale several times while it is still within the mother, the newborn may be more likely to accept or even appreciate the taste once it begins eating solid food. According to Robinson, research has previously shown that early exposure to a variety of foods helps 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.

According to Reissland, pregnant women who eat healthily may also notice that their children are less picky eaters. It could assist with their weight increase and their overall weight balance if we can genuinely teach them to prefer green veggies and maybe not like sweets so much, she added.