You are what your mother eats, study

Women who eat cereal for breakfast have an increased chance of having sons instead of daughters, a British study has found. Research by the Universities of Exeter and Oxford have uncovered strong links between higher energy intake among mothers around the time of conception and the birth of boys. "The consumption of breakfast cereals was also strongly associated with having male infants,'' the study said.

The study, published in the Proceedings of the Royal Society B: Biological Sciences journal, focused on 740 first-time mothers in the UK who did not know the gender of their unborn baby. The women were asked to provide records of their eating habits before and during the early stages of pregnancy. They were then split into three groups according to the number of calories consumed per day around the time they conceived.

Of the women in the group with the highest energy intake at conception, 56 per cent had sons, compared with 45 per cent in the group with the lowest calorie intake. As well as consuming more calories, women who had sons were more likely to have eaten a higher quantity and wider range of nutrients, including potassium, calcium and vitamins C, E and B12. The study's lead author, Fiona Mathews of the University of Exeter's School of Biosciences, said the findings could shed light on modern eating habits and birth statistics. "This research may help to explain why in developed countries, where many young women choose to have low calorie diets, the proportion of boys born is falling,'' Dr Mathews said.

While sex is genetically determined by fathers, the study indicated mothers appear able to favour the development of one sex of infant over another. While the mechanism is not yet understood, IVF research shows high levels of glucose encourage the growth and development of male embryos while inhibiting female embryos. Dr Mathews said there were implications for recent debates on whether to regulate so-called gender clinics that allow parents to select the sex of offspring, by manipulating sperm, for non-medical reasons. "Here we have evidence of a natural mechanism that means that women appear to be already controlling the sex of their offspring by their diet,'' she said. In animal studies, scientists have already established that more sons are produced when a mother has plentiful resources or is high ranking. "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,'' Dr Mathews said.

"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.''