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23 April 2008

Breakfast cereals boost chances of conceiving boys

Some people put a hammer under the pillow. Others try to ensure they conceive on the day of ovulation. Still others drink coffee, as this supposedly makes Y-chromosome carrying sperm swim faster. Now we can reveal a method that apparently really does affect the chances of having a boy: eat cereal for breakfast.

A survey of 740 pregnant women found that boys were slightly more likely if a women had high energy intake prior to conception, and that the individual food with most impact was breakfast cereal.

“If you want a boy, eat a healthy diet with a high calorie intake, including breakfast,” says Fiona Mathews of the University of Exeter in the UK, and lead researcher of the study.

She said it follows that the reverse is true for women who want girls, but on ethical grounds would not advise women to risk their health by skipping breakfast.


Intake of sodium, potassium and calcium was also a factor, providing partial support to the old wives’ tale that salty diets help women conceive sons.

Heavier boys

The insights came from detailed records of diets reported by the women before and during pregnancy.


Cereal intake had a bigger effect. “Of women eating cereals daily, 59% had boys, compared with only 43% who bore boys in the group eating less than a bowlful per week,” says Mathews.

The team’s results echo those in animals such as horses and cows, which are statistically more likely to bear males if well-fed.

The findings make evolutionary sense because baby boys are typically 100 grams heavier than baby girls, so female mammals may have evolved ways to favour production of boys when resources are plentiful.

Rich kids

One possible mechanism is that high glucose levels in the body of a well-fed woman favour survival of male rather than female embryos.

“It’s well known in IVF clinics that if you have high glucose concentrations in cell culture, it favours survival of male blastocysts,” says Mathews.

As for the finding that salt intake favours boys, one theory is that salt alters the acidity of the vagina to favour male sperm, but Mathew says there is scant evidence for this.

The researchers say that their findings might help explain slight reductions in male births in richer countries. In the UK, for example, the number of boys born is falling by 1 per 1000 births per year.

Eating habits

Mathews says that the findings might seem at odds with the obesity epidemic sweeping richer countries, but stressed that there were also problems with under-eating as well as over-eating. In the US, for example, the proportion of adults eating breakfast fell from 86 to 75% between 1965 and 1991. The fall for adolescent girls was steeper still, from 85 to 65%.

Mathews says that her findings provide hints of a cheap, “natural” way to select the sex of a child, although she stresses that much more research is needed to corroborate the results.

Lucilla Poston, who studies the impact of maternal nutrition on infant health at King’s College London, says that if there is an effect at all, it could be down to folate in cereals.

“Excess folate prevents defects in DNA through methylation, a chemical process of silencing some genes but not others,” she says. Maybe it plays a role in determining gender, but there’s no evidence for it, she says.

Journal reference: Proceedings of the Royal Society B: Biological Sciences (DOI: 10.1098/rspb.2008.0105)