There aren’t too many topics about pregnancy more controversial than what a mother-to-be can and can’t eat.
No sooner does a couple announce the news of an impending arrival
than a woman is bombarded with a list of rules about what she is and
isn’t allowed to put in her mouth.
“Don’t eat foods containing soft cheeses, cold meats, soft-serve
ice-cream, salads, raw egg, unwashed vegetables…but don’t worry, just
take it easy and enjoy the ride”. Yeah, right.
While this must drive women barmy, one question that’s always
intrigued me is about the flavour of the food. The mother and a
developing fetus are so tightly connected, an intriguing question is
whether a woman’s food choices during pregnancy can influence what the
child likes to eat after birth.
So, what science is out there?
Strange-Smelling Newborns
The first scientific hint that specific elements of a mother’s diet
may affect the developing baby came through intriguing reports from
hospitals of infants who were born with distinctive smells.
One of the most famous series of case studies
came from an Israeli team, who described four newborns with distinctive
odours reminiscent of a meal the mother ate just prior to giving birth.
Two mothers in this case series had given birth to babies that had a
distinct smell of cumin. After a quick quizzing, the mothers told the
researchers that in the days leading up to delivery they had both eaten
“schug”, which is a Middle-Eastern hot sauce containing cumin, garlic,
salt, oil and pepper. The newborn of another woman had a sharp odour of
fenugreek, a leguminous plant with seeds that have a slightly sweet,
nutty flavour. Similar questioning found that, just prior to delivery,
the mother had eaten a good serve of “hilbeh” – a Yemenite dish prepared
from fenugreek.
These case reports provide our first hint of evidence that this old
wives’ tale may indeed be true. A mother’s diet may have a lasting
effect on her baby.
The next step is to explore the biological mechanisms through which this may occur.
Flavouring The Amniotic Fluid
Food and drink that we ingest are broken down into small molecules by
our stomach and intestines, and are then absorbed and transferred to
our blood stream. During pregnancy, molecules in the mother’s blood
stream, including those that may produce a smell, can be passed to the
bloodstream of the fetus through the placenta and umbilical cord.
Inside the womb, the fetus sits within a membrane (amniotic sac) that
is filled with mucous-like fluid (amniotic fluid). The developing baby
is able to urinate into the amniotic fluid, which means that at least a
portion of the odorous molecules that originated with the mother can be
transferred to the baby via the placenta and umbilical cord, and end up
in the amniotic fluid. After bathing in a sac full of smelly fluid for
forty weeks, it would be no wonder that a fetus would also come out of
the sac with a bit of a pong.
Julie Mennella and colleagues from the United States were the first to demonstrate experimentally
that a woman’s diet can change the odour of the amniotic fluid in the
womb. The researchers identified ten women who were about to undergo a
routine amniocentesis. Amniocentesis is a procedure in which a small
sample of amniotic fluid is drawn out of the amniotic sac by a large
needle to undergo medical testing. All of the women were in the second
trimester of their pregnancy.
About forty-five minutes before their amniocentesis, five women were
asked to swallow a capsule that contained garlic extract, while the
other five woman swallowed a capsule containing milk. The researchers
then formed an “odour panel” of thirteen adults, who were presented with
one sample of amniotic fluid obtained from a woman who ingested a
garlic capsule, and one from a woman who ingested a milk capsule. The
panel didn’t know which sample was from which woman, and their job was
to make as series of judgements about which of the two samples smelt
more like garlic.
The results were unequivocal. Almost without exception, the judging
panel chose the sample of amniotic fluid of the women who ate the garlic
capsules as smelling more garlic-like. The garlic extract that the
women took prior to the amniocentesis had made their amniotic fluid take
on that smell.
The reason it is important for us to know that amniotic fluid can be
“flavoured” is because by the second trimester of pregnancy, a fetus is
able to swallow amniotic fluid. A near-term fetus can swallow up to 1000
ml of amniotic fluid
per day, which is about 50% of the entire volume of fluid in the sac.
The swallowing not only helps regulate the amount of fluid in the
amniotic sac, but can also assist with the development of the baby’s
digestive and respiratory systems.
Is it possible that by swallowing flavoured amniotic fluid in the
womb, infants develop a preference for those flavours after birth?
Testing Smell Preferences
Of course, it is not just our sense of taste that is vital to our perception of flavour, but also our sense of smell.
The “swallowing” of amniotic fluid through the oral and nasal passages during prenatal life
means that odorous molecules in the amniotic fluid have access to
olfactory (smell) receptors in the nose. It is possible that exposure to
these “smells” in utero lead infants to be more attracted to these
smells after birth?
This idea was investigated
by a French research group. Two groups of pregnant women were recruited
based on their preference for aniseed (liquorice) flavoured food. The
first group comprised twelve women who liked the taste and regularly
consumed aniseed-flavoured food and drink, while the second group of
twelve women never consumed foods or drink with this flavour. In the
final two weeks of pregnancy, the first group of women were provided
with aniseed lollies, cookies and drinks just to make sure that they
consumed a decent amount of this flavour.
Immediately after the infants were born, the infants had two
cotton-tipped swabs held under their nose, one after the other. One swab
had been dipped in aniseed flavoured syrup, and the other was dipped in
paraffin oil. The researchers then videotaped how the newborn infants
responded to the different tastes.
The infants whose mothers regularly consumed aniseed during pregnancy
spent more time “mouthing” (mouth opening, sucking, tongue protrusion)
towards the aniseed swab than towards the paraffin swab. They also
directed far more distaste towards the paraffin swab than the aniseed
swab. In comparison, the infants of the mothers who didn’t consume
aniseed during pregnancy spent an equal amount of time mouthing at each
of the two swabs, indicating no preference for either smell.
Testing Food Preferences
The next link in the chain is to determine whether foods eaten during pregnancy influence the taste preferences of infants.
Julie Mennella and colleagues have provided the best test
of this idea to date in their study of twenty-nine pregnant women.
Fifteen of these women were ask to drink 300 ml of carrot juice for four
days a week for three consecutive weeks during their last trimester of
pregnancy. The remaining fourteen women were asked to refrain from
eating carrots, and drink 300 ml of water during for that same time
period.
The second part of the experiment took place about five to six months
after the babies had been born, coinciding with the time that solid
foods were being introduced into the babies’ diets. At around this time,
researchers paid two visits to the family, with each visit focusing on
how the child reacted to certain foods during feeding time. At one of
the visits, the mother was asked to feed the infant cereal mixed with
carrot juice, while during the other visit the mother fed the child
cereal mixed with water (“plain cereal”). The mothers were asked to feed
the infants as they usually would until the baby refused the cereal
three consecutive times.
The results of the study clearly indicated that the infants whose
mothers drank carrot juice during pregnancy responded differently to the
cereal mixed with carrot juice. These infants showed significantly
fewer negative facial expressions for the carrot-flavoured cereal
compared with the plain cereal. In comparison, the control infants whose
mothers drank water during pregnancy had the same number of negative
facial expressions for both the carrot-flavoured and plain cereal.
Furthermore, the mothers who drank carrot juice during pregnancy –
who were unaware of the hypothesis of the study – believed that their
infants enjoyed the carrot-flavoured cereal more than the plan cereal.
In comparison, the mothers who drank water felt that their infants had
no preference for either cereal.
Myth Or Reality?
Well-designed studies have found that a mother’s diet during
pregnancy can change the odour of the amniotic fluid in which a fetus
grows. When the fetus swallows this fluid, the olfactory (smell)
receptors in the nose are exposed to these odorous molecules. The fetus
is then familiar with these “smells” and so will have a preference for
foods with these flavours once they are born. Truly marvellous!
See more : http://topreveal.com/easy-diy-baby-food-recipes
See more : http://topreveal.com/easy-diy-baby-food-recipes
