Video: Does your diet determine your baby's sex?

By JoNel Aleccia Health writer
msnbc.com
updated 4/25/2008 11:39:20 AM ET 2008-04-25T15:39:20

In the quest to select a baby’s sex, success could depend on breakfast cereal and better nutrition, according to a new study that may offer some women another reason to eat their Wheaties.

Mothers-to-be who skip breakfast and eat less are more likely to give birth to girls, while moms who consume more calories and a wider range of nutrients  — including, specifically, those from breakfast cereal — are more likely to deliver sons.

That’s according to new research by British scientists that provides what they say is the first-ever evidence that a mother’s diet at conception may determine her baby’s sex.

Researchers from the universities of Exeter and Oxford in England asked 740 first-time moms in the United Kingdom to keep food diaries before and during early pregnancy. The women didn’t know the sex of their babies, but when researchers reviewed their food plans, they found that moms who consumed more calories of higher quality before conceiving were about 24 percent more likely to give birth to boys than moms who ate less.

“The overall sex ratio in our population was close to 50:50, but individual mothers had a greater chance of bearing male offspring if their nutrient intake was high prior to conception,” wrote Fiona Mathews, the study’s lead author and a research fellow at the University of Exeter. “The consumption of breakfast cereal was also strongly associated with having a male infant.”

Fifty-six percent of women in the group with the highest energy intake gave birth to boys, compared to 45 percent in the group with the lowest energy consumption, according to the study.

Mothers of boys consumed an average of 2,413 calories a day before conception and higher amounts of foods containing potassium, calcium and vitamins C, E and B12, the researchers said. Women who had girls logged 2,283 calories a day and less protein, vitamins and minerals.

Odds of having a boy were much higher for women who ate at least one bowl of breakfast cereal a day compared to women who ate less than one bowl a week, the study said. Breakfast cereals are usually fortified by vitamins and minerals.

Critics wary of claims
Critics, however, said the new research contradicts basic facts of human genetics. A father’s sperm determines a child’s sex, and there’s no evidence that maternal nutrition has anything to do with it, said Dr. Paul Magarelli, vice president of the Pacific Coast Reproductive Society.

“A correlation does not make the truth,” said Magarelli, who is also director of the Reproductive Medicine and Fertility Center in Colorado Springs, Colo. “I think it’s a spurious correlation, that’s all I can say.”

The British scientists said that although fathers do determine sex, their research indicates that mothers’ may be able to favor the development of one sex over another, perhaps in the way that high-glucose environments in in-vitro fertilization appear to favor male embryos and inhibit female embryos.

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The research is also supported by an evolutionary drive to produce more offspring in times of plenty. In many animals — including horses, cows and some species of deer — more males are produced when a mother has more resources, the scientists noted.

Skipping breakfast, for instance, extends overnight fasting and depresses glucose levels, which could be interpreted by the body as a poor environment, researchers said.

Their argument deserves further study, said Dr. Tarun Jain, an assistant professor of reproductive endocrinology at the University of Illinois at Chicago. Jain said his initial response to the study topic was skeptical, but that it changed after he read a draft of the report to be published Wednesday in the Proceedings of the Royal Society B: Biological Sciences, a British journal.

“It’s not showing far and away that if women eat a certain diet they’ll have a boy or a girl, but it certainly is giving us some information,” Jain said. “Could there be dietary factors that influence conception?”

Diet trends may explain fewer boys
In addition to suggesting that breakfast cereal may produce more boys, the researchers said that nutrition and diet trends may account for an incremental decline in male births in developing nations. Over the last 40 years, births of boys have also dropped by about 1 per 1000 births annually in the United States, the U.K. and Canada, they said.

At the same time, many young women in those developed nations have begun skipping breakfast and eating poorer-quality diets.

“This research may help explain why, in developed countries, where many young women choose to have low-calorie diets, the proportion of boys born is falling,” Mathews said.

That's counter to the trend in countries such as India, Vietnam and China, where births of boys now outpace girls because parents selective sex techniques, including abortion, to obtain highly prized sons.

The new study may influence mothers to try to use nutrition to select sex, which worries ethicists such as Nigel Cameron, president of the Institute on Biotechnology and the Human Future at the Chicago-Kent College of Law at the Illinois Institute of Technology.

"It adds to the manipulative tool box whose purpose is designer babies," said Cameron, adding: "We need a lot more social debate about the fact that children should be received as-is."

Whether the research deserves further study or not, at least one mother said it supports teachings women in her family have followed for generations.

If a woman wants to conceive a boy, everyone knows she should eat more meat and other high-protein foods, as well as foods rich in potassium, vitamins and salt, said Jessica McCurdy Crooks, a freelance writer and records manager who divides her time between Jamaica and Florida.

When Crooks, 43, decided to become pregnant, she adapted her vegetarian diet to include more beans, peas and salty foods in hopes of conceiving her son, Jalen, now 3.

“I ended up having a soft spot for boys,” said Crooks, who raised four brothers. “And I had a boy."

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