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MU professor Michael
Roberts is researching whether a woman can control the
sex of her baby by what she eats.
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Diet
Affects Sex of Offspring
By Matt McGowan
Anecdotal evidence suggests that maternal
diet in mammals may influence the sex of their offspring. For
many years scientists have observed that female animals in the
wild tend to produce more male offspring if they are well fed.
Still, the influence of diet on the sex of offspring is a controversial
issue. Michael Roberts, a Curators’ Professor of animal
sciences at the University of Missouri-Columbia, is cautious
to say whether the research in his lab settles this controversy.
Working primarily with mature mice, Roberts
and his research team demonstrated that diets high in saturated
fat contributed to a predominance of male offspring. Conversely,
when fed a diet that was low in saturated fat and high in carbohydrates,
mothers produced more female pups. The controlled diets were
fed to the mothers and not to the fathers. Roberts said that
other than varying the saturated fat and carbohydrate levels,
the diets were nutritionally balanced. Also, the mice had unlimited
access to food.
Roberts’ study, which will be published
in the Proceedings of the
National Academy of Sciences, is important because
it proves that sex ratios in offspring can be altered without
nutritional stress on the mother. Previous experiments concentrated
on limiting food supply rather than manipulating nutritionally
complete diets.
“Previous studies with mice have demonstrated
that food restriction of the mother skews the sex ratio of her
offspring toward females,” said Roberts. “But these
studies also reduced litter size, suggesting that male fetuses
are more susceptible than females to maternal under-nutrition.”
In Roberts’ study, gestation length
and litter size did not vary between the diets. Initially, Roberts
was not impressed with the data. In the first round of breeding,
ten-week-old mice produced roughly the same number of male and
female offspring. However, during the next three rounds of breeding,
mature mice — those older than 20 weeks — on the
high-fat diet produced litters with a 2-to-1 ratio in favor
of males, while the reverse was true for mothers on the low-fat,
high carbohydrate diet. Thus, age of the mothers was an important
variable.
Roberts cannot explain exactly why the different
diets influenced sex of the mice offspring, but he thinks at
least two possibilities may be at work. He suspects the high-fat
diet may create hormonal changes that affect the reproductive
tract of the female. In this scenario, it is possible that the
Y chromosome-bearing sperm are better able to fertilize with
the high-fat diet. A more plausible explanation, Roberts says,
is that changes in the reproductive-tract environment could
lead to a selective loss of embryos of one sex over the other
before they implant into the wall of the uterus.
“The big test is going to be whether
we can use this research from a practical point of view in livestock,”
Roberts said. “But clearly, it has implications to all
mammals. Ultimately, we have to ask, ‘is there any way
a woman could control the sex of her baby by what she consumes?’
Of course, we don’t know this and can’t test it.”
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Last Update:
November 15, 2007
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