Prenatal learning: Do "pregnancy foods" affect children's eating preferences?
© 2009 - 2013 Gwen Dewar, Ph.D., all rights reserved
Opportunities for prenatal learning
A fetus begins swallowing amniotic fluid at around 12 weeks, and
by 28 weeks, an unborn baby is developing a powerful sense of smell (de
Vries et al 1985).
So might babies learn about odors and flavors before they are born?
The phenomenon has been documented in rodents and rabbits (Bilko
et al 1994; Hepper 1988). And there’s evidence for prenatl learning in
humans as well.
For instance, babies recognize the smell of their own amniotic
fluids immediately after birth. Given the choice, newborns prefer
breasts that have been dabbed with fluids from their amniotic sac
(Varendi et al 1996).
But babies lose their preference for the scent of amniotic fluid
within a few days after birth. What about long-term effects? Can
prenatal learning influence baby behavior weeks--even months--after
The evidence suggests that it can. And that might mean that a mother's
diet during pregnancy can shape the food preferences of her children --
for good or for ill.
In one experiment, Julie Mennella and her colleagues asked 46 pregnant women to follow one of three regimens:
- Drink carrot juice during the pregnancy and stop after the baby is born
- Drink water during the pregnancy and begin drinking carrot juice after the baby is born
- Avoid carrot juice before and after the pregnancy (i.e., drink water only)
The “carrot juice during pregnancy only" condition permitted researchers to test for the effects of flavored amniotic fluid.
The “carrot juice after pregnancy" condition allowed researchers to test for the effects of consuming breast milk that may carry the flavor of carrots.
More than five months after the babies were born--when the babies
were just starting to eat cereal, their first solid foods--the
researchers tested the infants’ flavor preferences.
They gave the babies two kinds of cereal, plain and carrot-flavored.
Would the babies exposed to carrots in utero prefer carrot-flavored cereal? They seemed to.
Compared with their reactions to plain cereal, the
prenatally-exposed babies made fewer negative facial expressions while
they ate carrot-flavored cereal (Mennella et al 2006).
The results were similar for the babies who had been exposed to
carrot-flavored breast milk. But there was no effect observed for babies
whose mothers had never drank carrot juice.
Can prenatal learning put kids at risk for bad habits?
It seems that prenatal learning about food has long-term effects, and
this might help babies get over their initial resistance to eating
healthful, new foods.
But the effect may have a dark side, too. Studies show that rodents exposed to alcohol in utero are
more attracted to alcohol-tainted water after they are born. In fact,
newborn rats show as much attraction to the odor of alcohol as they do
to the smell of their own amniotic fluid (Abate et al 2008).
For obvious reasons, no one has ever done a comparable experiment
on humans. But one observational study suggests that babies born to
women who drank moderate amounts of alcohol during pregnancy have more
pleasurable reactions to the smell of alcohol (Faas 2001).
And several epidemiological studies have found a link between
fetal alcohol exposure and alcoholism later in life--even when
researchers controlled for genetics and postnatal environmental factors (see Abate et al 2008 for a review).
So in addition to the dangers that alcohol poses for fetal health
and brain development, it appears that prenatal alcohol exposure might
give babies a lasting taste for alcohol.
Prenatal learning about junk food?
This makes me wonder how other bad habits might affect baby taste preferences.
Research on rats suggests that a pregnancy diet of high-fat,
high-sugar foods (including potato chips and jelly doughnuts) might
affect the food preferences of babies (Bayol et al 2007).
And other studies have found that feeding pregnant rats high-fat,
high-sugar "junk" food -- like cookies, cheese puffs, sweetened
breakfast cereals, and processed meats -- altered the reward system of
their offsprings' brains.
Compared to rat pups whose mothers ate a standard, healthful
diet, the "junk food" pups developed opioid-signalling (reward) pathways
that were less sensitive to junk food triggers. As a result, these pups
would have to eat more sugary, high-fat food to get the same "rush" of
dopamine that makes eating such food so pleasurable (Ong and Muhlhausler
2011; Gugusheff et al 2013).
But in these studies, rat mothers ate "junk" food every day throughout their pregnancies.
It should also be noted that the carrot juice study involved the daily consumption of carrot juice.
If the women had drunk carrot juice only 2-3 times a month, would their babies have responded the same way?
We just don’t know. But I suspect that pregnant women eating
otherwise healthful diets don’t have to worry that the occasional jelly
doughnut will program their babies to love junk food. What we ought to
be cautious about is the regular consumption of alcohol and sugary,
high-fat, processed foods.
What else do babies learn in the womb?
Studies reveal that newborn babies can distinguish their mothers'
voices from those of other women. And experiments have shown that
babies are also born with a preference for certain speech rhythms--those
matching the language of their mothers. So it seems that fetuses are
listening to their mother's voices before they are born.
You can read more about
these clues to prenatal learning in my article "The social world of the newborn."
And more for information about what shapes baby's feeding preferences, see my article about
flavors in breast milk and formula
as well as this article about
getting babies to eat new foods.
References: Prenatal learning about food
Abate P, Pueta M, Spear NE, and Molina JC. 2008. Fetal learning about
ethanol and later ethanol responsiveness: evidence against "safe"
amounts of prenatal exposure. Exp Biol Med (Maywood). 233(2):139-54.
Bayol SA, Farrington SJ, and Stickland NC. 2007. A maternal 'junk
food' diet in pregnancy and lactation promotes an exacerbated taste for
'junk food' and a greater propensity for obesity in rat offspring. Br J
Bilko A, Altbacker V, and Hudson R. 1994. Transmission of food
preference in the rabbit: The means of information transfer. Physiology
and Behaviour 56: 907-912.
de Vries JIP, Visser GHA, and Prectl IIFR. 1985. The emergence of
fetal behaviour II. Quantitative aspects. Early Human Devel 12:99-120.
Gugusheff JR, Ong ZY, and Muhlhausler BS. 2013. A maternal
"junk-food" diet reduces sensitivity to the opioid antagonist naloxone
in offspring postweaning. FASEB J.27(3):1275-84.
Hepper PG. 1988. Adaptive fetal learning: prenatal exposure to garlic affects postnatal preference. Animal Behav 36:935-6
Mennella JA, Jagnow CP, Beauchamp GK. 2001. Prenatal and Postnatal Flavor Learning by Human Infants. Pediatrics. 107(6):E88.
Ong ZY and Muhlhausler BS. 2011. Maternal "junk-food" feeding of
rat dams alters food choices and development of the mesolimbic reward
pathway in the offspring. FASEB J. 25(7):2167-79
Varendi H, Porter RH, Winberg J. 1996. Attractiveness of amniotic
fluid odor: evidence of prenatal olfactory learning? Acta Paediatr.
Content of "Prenatal learning" last modified 4/13