Apparently, carnivorous mothers give birth to boys and chocolate-addicted ones to girls. But even if seems funny, what a mother eats seems to really bias the sex of her offspring, as revealed by a new research published in Proceedings of the Royal Society B. Low blood-sugar amounts seem to boost the birth of females. It seems that gender is not just an issue of sex chromosomes. Earlier researches had pointed that single mothers are more likely to have daughters.

The team led by Elissa Cameron at the University of Pretoria in South Africa controlled levels of blood glucose in female mice during breeding period, by delivering to them a steroid named dexamethasone (DEX), which stops the glucose passing into the bloodstream.

20 females received water with DEX during the first three days when they were exposed to males, after which they received plain water. Blood-glucose amounts of these mice and another 20 control females were checked several times during the trial. In mice treated with DEX the value decreased on average from 6.47 to 5.24 millimoles/litre.

While 53% of the control females' offspring were male, the number dropped to 41% in the case of the DEX treated females. Researchers could not explain what causes this correlation, but the opposite also proved real, as a research made on diabetic mice connected high blood-glucose amounts to an increased number of male offspring.

For the moment, we can only speculate. Probably female offspring represent an advantage in times of shortage, as weak males are less likely to reproduce, while females deliver offspring not conditioned by their sexual fitness. The team noted that the findings match some folk wisdom saying that mothers have to eat a lot of red meat and salty snacks if they want to have a boy, and fish, vegetables, chocolate and sweets if they want to give birth to a girl. "This is interesting, since meat raises blood sugar for a sustained period of time, whereas sugar-based snacks raise blood sugar very high, but for a short amount of time, followed by a slump in blood glucose", Cameron told New Scientist.