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Podcast Transcript: Considering getting pregnant and want to influence whether you have a boy or a girl? According to new research published in the Proceedings of the Royal Society, you might want to check out your diet. Scientists at the Universities of Exeter and Oxford in England followed 750 first-time pregnant women. The women were asked about their eating habits before and during pregnancy. They were split into three groups based on the sheer number of calories consumed and the healthfulness of their diets.
For the women who consumed more calories and received a wider range of nutrients, 56 percent had boys. This group was also the most likely to eat breakfast. Among the women with the lowest caloric intake, only 45 percent had boys.
The study is the first linking sex determination with diet in humans. Although it’s been known in some animals that more calories equals more males. And while those of us in the West have plenty of calories available, in the US and UK the boy-to-girl ratio has been slipping. Possibly because mothers are on low-calorie diets or are skipping breakfast.
—Cynthia Graber
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9 Comments
Add CommentCorrelation does not equal causation! This is such a basic scientific concept, and yet Scientific American has made such a sophomoric error and perpetuated this misunderstanding!
Reply | Report Abuse | Link to thisRecords of eating a certain type of food and having a certain gender of baby does NOT mean that the food CAUSED the gender. It is just as likely that the gender of the fetus influenced the dietary inclinations of the mother!
Holy crap. This is the dumbest thing I have ever heard. You consume more calories because you are having a boy, not the other way around. Come on.
Reply | Report Abuse | Link to thisThis doesn't sound scientific at all. The diet after pregnancy has no possible way of changing the Y chromosome that came from the father into an X. As for the diet before pregnancy, it's still very, very unlikely for it to increase the possibility of fertilization by a Y-chromosome sperm instead of an X-chromosome sperm. The gender is determined by the father's sperms not by the mother. That shouldn't be too hard to see!
Reply | Report Abuse | Link to thisThere is a valid theoretical explanation for why calorie intact at conception (not after conception) could effect the sex of the offspring. In species where males compete for females, females will only reproductively benefit from having a male if they have enough resources to have a large, competitive male. If a female has reduced access to resources, she is better off having a female, since a small female will be more likely to reproduce than a small male. This has been demonstrated in other organisms and could be true in humans as well. True, correlation doesn't imply causation, but correlation is often the first step to finding causes, so such studies are still valuable.
Reply | Report Abuse | Link to thisYes, sex appears to be ultimately determined by whether an X or Y sperm fertilizes the egg, but as long as conception occurs inside the females' body she has some ability to manipulate which type of sperm enters the egg. By changing the pH or viscosity for example, her body could create an environment more favorable for one sperm type or the other, increasing her chances of having one sex or the other. This has obviously not been proven - but the potential is certainly there.
Reply | Report Abuse | Link to this56% of women having boys doesn't seem like a very solid statistic to base the correlation between diet and sex on - the chance of having a boy is still 50:50. How is this a definitive study?
Reply | Report Abuse | Link to thisI interviewed Fiona Matthews, who headed this study on my blog. http://www.skepticdad.wordpress.com. Please come and comment about your doubts on the interpretations on the data.
Reply | Report Abuse | Link to thisI'm glad people are bringing up the fact that this research is dubious. As far as I have understood, the presence of an X or Y chromosome in the fertilizing sperm is what determines the sex, not the mother's diet after conception. I am baffled that it is being considered. Can it be that the study refers to just sexual development as opposed to sex determination?
Reply | Report Abuse | Link to thisHowever, I've also heard in the past (I haven't substantiated this) that womb environment can determine [i]sexuality[/i]? How true is this? Could there be an epigenetic contribution?
[b]Edit:[/b] TickTock I just went to your blog and read the interview. Fiona states that [i]pre-pregnancy[/i] diet was what was important. Which definitely makes more sense.
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Edited by miuixtli at 05/05/2008 3:05 AM
Rosenfeld, C. S., Grimm, K. M., Livingston, K. A., Brokman, A. M., Lamberson, W. E., & Roberts, R. M. (2003). Striking variation in the sex ratio of pups born to mice according to whether maternal diet is high in fat or carbohydrate. Proceedings of the National Academy of Sciences, 100(8), 4628-4632. (10.1073/pnas.0330808100)
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