Voeding van invloed op geslacht baby*
Volgens een Zuid-Afrikaanse studie, weliswaar met muizen lijkt het erop dat aanstaande moeders wellicht het geslacht van hun baby kunnen beïnvloeden door op hun voeding te letten in de tijd voor de bevruchting. Met een dieet dat rijk is aan eiwitten en dierlijke vetten lijkt de kans op een jongen groter, en als er meer suikers gegeten worden geeft dat een grotere kans op een meisje. Het bloedsuikergehalte van de helft van de dieren werd door speciale voeding verlaagd waarna bleek dat 41% van de muizen mannelijke nakomelingen kregen tegen 53% bij de muizen die geen aangepaste voeding gekregen hadden. Voeding rijk aan eiwitten en dierlijke voeding geeft langere tijd een hogere bloedsuikerwaarde terwijl suikerrijke voeding even een piek omhoog in de bloedsuikerwaarde geeft en daarna een lagere bloedsuikerwaarde.
Diet may influence the sex of your baby
A mother’s diet in the run-up to conception could influence the sex of her child, suggests a study in mice. The research shows that mice given drugs to lower their blood-sugar levels produced significantly more female than male pups.
The findings lend credence to traditional beliefs that eating certain foods can influence the sex of offspring.
The conventional wisdom is that the father’s sperm is the main determinant of the sex of a child. But increasingly scientists have found hints that maternal factors might have an influence too. For example, earlier work has suggested that single mothers are more likely to give birth to daughters.
Elissa Cameron at the University of Pretoria in South Africa and her colleagues wanted to study how changes in diet might influence sex ratios – the proportion of males to females in a population.
To do this, they altered the levels of blood-sugar in female mice during conception, by feeding the mice a steroid called dexamethasone (DEX), which inhibits the transport of glucose into the bloodstream.
Evolutionary advantage
The scientists gave 20 female mice water dosed with DEX for the first three days that the females were exposed to males. Afterwards, the mice were given plain water. Cameron’s team measured the blood-sugar levels of these mice, as well as that of 20 control females several times during the experiment.
The average blood-glucose levels in mice that received DEX dropped from 6.47 to 5.24 millimoles/litre. And the team found that 53% of the pups born to the control females mice were male, but only 41% of those born to the mice receiving DEX were male.
Exactly how a drop in blood sugar causes more female births remains unclear. But the opposite also seems to work. A previous study involving diabetic mice, found that rodents with high blood-sugar levels produced more male offspring than expected.
Biologists have theorised that mothers may give birth to more female offspring during times of stress or ill health, because it confers an evolutionary advantage. If the stressed mother gave birth to a weak male, he is unlikely to mate. But if the child was female, no matter how weak, she would likely bear more children.
Fitness marker
“It does seem that sugar levels could act as an indicator of whether a mother is in a good state or bad state,” says Ruth Mace at the University College London, UK. Mace previously published a study that found mothers with more muscle mass are more likely to give birth to sons during food shortages.
The idea of diet influencing sex ratio is already part of traditional wisdom. Folklore says that mothers should eat more red meat and salty snacks if they want a boy, and fish, vegetables, chocolates and sweets if they want 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,” says
Cameron.
Journal reference: Proceedings of the Royal Society B (DOI:
10.1098) (Februari
2008)
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