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Do regular breakfasts boost baby boy numbers? Christine McGourty reports
A woman's diet around the time of conception may influence the gender of her
baby, research suggests.
The study suggests a high calorie diet at this time - and regular breakfasts -
might increase the odds of a boy.
The researchers say the modern trend to opt for low calorie diets might explain
why the proportion of boys is falling in developed countries.
The study, by the Universities of Exeter and Oxford, appears in the Royal
Society journal Biological Sciences.
The study focused on 740 first-time pregnant mothers in the UK, who were asked
to provide records of their eating habits before and during the early stages of
pregnancy.
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
Dr Fiona Mathews
University of Exeter
The researchers found 56% of women with the highest energy intake around the
time of conception had boys, compared to just 45% among women with the lowest
energy intake.
Women who had sons were also more likely to have eaten a higher quantity and
wider range of nutrients, including potassium, calcium and vitamins C, E and
B12.
They were also more likely to have eaten breakfast cereals.
Fewer boys
Over the last 40 years there has been a small but consistent decline, of about
one per 1,000 births annually, in the proportion of boys being born in
industrialised countries, including the UK.
Previous research has also shown a reduction in the average energy intake in
the developed world, and there is also evidence that more people now skip
breakfast.
Scientists already know that in many animals, more males are produced when a
mother has plentiful resources or is high ranking.
The phenomenon has been most extensively studied in invertebrates, but is also
seen in horses, cows and some species of deer.
The explanation is thought to lie with the evolutionary drive to produce
descendants.
Lead researcher Dr Fiona Mathews said: "Potentially, males of most species can
father more offspring than females, but this can be strongly influenced by the
size or social status of the male, with poor quality males failing to breed at
all.
I would urge women to not to start starving themselves in order to try
influence the sex of their baby
Dr Allan Pacey
University of Sheffield
"Females, on the other hand, 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.
"However, in leaner times having a daughter is a safer bet."
Glucose levels
It is known from IVF research that high levels of glucose encourage the growth
and development of male embryos while inhibiting female embryos.
In humans, skipping breakfast depresses glucose levels and so may be
interpreted by the body as indicating poor environmental conditions and low
food availability.
Dr Allan Pacey, an expert in fertility at the University of Sheffield, said
there was good evidence that nature had subtle ways of changing the sex ratio
of a population in response to a variety of circumstances.
However, he said: "I would urge women to not to start starving themselves in
order to try influence the sex of their baby.
"It has been observed in some animal studies that even small changes in female
diet can affect the life long health of the offspring, so it is important that
the mother has appropriate nutrition at the time of conception and throughout
her pregnancy."