Expecting fathers, hoping to have a baby boy, may consider pampering their wives with fancy breakfasts in bed, as it may be the only method known to science to help influence the sex of the child. Scientists at the Universities of Exeter and Oxford found a correlation between a mother’s high energy diet and an increased chance of having a male child.
The study focused on 740 first-time pregnant mothers in the UK, who did not know the sex of their fetus. They 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. 56% of the women in the group with the highest energy intake at conception had sons, compared with 45% in the lowest group. 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. There was also a strong correlation between women eating breakfast cereals and producing sons.
Over the last 40 years there has been a small but consistent decline, of about one per 1000 births annually, in the proportion of boys being born in industrialised countries, including the UK, the USA and Canada. Previous research has also shown a reduction in the average energy intake in the developed world. The ‘obesity epidemic’ is largely ascribed to declines in physical activity and differences in food quality and eating habits. There is also evidence that skipping breakfast is now common in the developed world: in the USA, the proportion of adults eating breakfast fell from 86% to 75% between 1965 and 1991.
Dr Fiona Mathews of the University of Exeter, lead author on the paper, said: “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. Our findings are particularly interesting given the recent debates within the Human Fertilisation and Embryology Committee about whether to regulate ‘gender’ clinics that allow parents to select offspring sex, 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.”
Scientists already know that in many animals, more sons 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.
University of Exeter press release: You are what your mother eats …
Abstract: You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans Proc. R. Soc. B