Oysters may excite the libido, but there is
nothing like a hearty breakfast laced with sugar
to boost a woman's chances of conceiving a
son, according to a recent study.
Likewise, a low-energy diet that skimps on
calories, minerals and nutrients is more likely
to yield a female of the human species, says
the study, published in Proceedings of the Royal
Society B: Biological Sciences , Britain's de facto
academy of sciences.
Fiona Mathews of the University of Exeter in
Britain and colleagues wanted to find out if a
woman's diet has an impact on the sex of her
offspring. So they asked 740 first-time mothers
who did not know if their unborn foetuses were
male or female to provide detailed records of
eating habits before and after they became
pregnant.
How the study was done
The women were split into three groups
according to the number calories they
consumed per day around the time of
conception.
Fifty-six percent of the women in the group
with the highest energy intake had sons,
compared to 45 percent in the least-well fed
cohort. Beside racking up a higher calorie
count, the group who produced more males
were also more likely to have eaten a wider
range of nutrients, including potassium,
calcium and vitamins C, E and B12.
The odds of an XY, or male outcome to a
pregnancy also went up sharply "for women
who consumed at least one bowl of breakfast
cereal daily compared with those who ate less
than or equal to one bowl of week," the study
reported.
These surprising findings are consistent with a
very gradual shift in favour of girls over the last
four decades in the sex ratio of newborns,
according to the researchers.
Previous research has shown - despite the
rising epidemic in obesity - a reduction in the
average energy uptake in advanced economies.
The number of adults who skip breakfast has
also increased substantially.
What the findings mean
"This research may help to explain why in
developed countries, where many young
women choose low calorie diets, the proportion
of boys is falling," Mathews said.
The study's findings, she added, could point to
a "natural mechanism" for gender selection.
The link between a rich diet and male children
may have an evolutionary explanation. For
most species, the number of offspring a male
can father exceeds the number a female can
give birth to. But only if conditions are
favourable - poor quality male specimens may
fail to breed at all,whereas females reproduce
more consistently.
"If a mother has plentiful resources, then it can
make sense to invest in producing a son
because he is likely to produce more
grandchildren than would a daughter," thus
contributing to the survival of the species,
explains Mathews.
"However, in leaner times having a daughter is
a safer bet." While the mechanism is not yet
understood, it is known from in vitro
fertilisation research that higher levels of
glucose, or sugar, encourage the growth and
development of male embryos while inhibiting
female embryos.
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