A low fat diet with periods of long fasts favours girls, the researchers have found.

The findings seem to give some credence to to old wives’ tales such as eat “bacon for boys”.

Dr Cheryl Rosenfeld, of the University of Missouri, and colleagues said: “High calorie diets generally favour birth of males over females, whereas low calorie diets tend to favour females over males.

“In humans and mice, food restriction and a suboptimal diet during the period around conception and early pregnancy also lead to a surfeit of daughters, most probably due to selective loss of male foetuses, the most vulnerable sex in the womb.”

Researchers analysed the genes in placentas of pregnant mice fed diets high in fat or carbohydrates and low calorie diets and found each one had a distinctive effect compared with a third group given normal soybean meal-based food.

As well as the changes in sex, female foetuses were more sensitive to their mother’s diet and their genes were more likely to be affected or altered, it was found.

After 12 days – just over half the animals’ pregnancy term – there were differences in almost 2,000 genes including those involved in kidney function and smell.

They concluded gene expression in the mouse placenta is “adaptive and shaped by maternal diet” with the biggest effect on the placentas of females.

The research, published in Proceedings of the National Academy of Sciences, follows a study two years ago that found a woman’s diet around the time of conception may influence the gender of her baby… Continue reading