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Published online 22 April 2008 | Nature | doi:10.1038/news.2008.769
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An appetite for sex
Calorie intake before conception may mean the difference between boys and girls.
The sex of new babies is influenced by the mother's diet before she conceives, a new study suggests. According to a survey of 740 British mums to be, a high-calorie diet is more likely to lead to a baby boy in nine months' time.
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How did this end up in Nature News. The sex of the baby is determined by the sperm and thus the male, not the femail...
WTF? I've read it again and I also see nothing about sperm! If the assumption of this piece is that the female ovulates more than one ovum and all ova are fertilized by sperm, some eggs given a Y chromosome and an X, and that THEN conditions of the uterus may favor the male embryo, the article would make some sense. However, there's really no mention of this. From my Doctorate in Medicine, I don't recall that women normally ovulate several ova at a time.
Joster & Michael - My understanding was this- we know that not all fertilized eggs will make it all the way to birth, often times due to the conditions in the womb. This article explains how those conditions in the womb could be affected by the mother's diet, and how different conditions could favor male vs. female embryos. It's not about selective fertilization, but survival of an embryo after that point.
Hello, I wrote this story, and perhaps what I should have made clearer is that this is about subtle differences that make a woman's body more accommodating to either a female or male embryo - small effects that only become noticeable when hundreds of births are taken into account. Yes, women typically only release one egg at a time, and at the point of fertilization it is the single sperm that enters it that determines its sex. But many fertilized embryos do not make it to full pregnancy, perhaps because they are spontaneously aborted or fail to implant. What this study seems to imply is that a woman's diet can make it more or less likely that an embryo of a particular sex will survive and become a foetus and ultimately a baby. (A more acidic womb environment, for example, is thought to be more conducive to hosting a male embryo.) Remember that this is to do with a woman's general diet, so there do not have be two fertilized eggs in the womb at the same time. A woman might, for example, conceive and reject a female embryo one month, and then conceive and implant a male one the next. It is these effects that, although small when compared with the sex-determining power of sperm genetics, are showing up in the data here. Because it's a small effect, the numbers in every case do not diverge too far from a 50:50 split between the sexes - whether or not the mother eats breakfast. mike
This study is a case study in bad usage of statistics, and how faulty articles with bad statistics can pass peer review. Look at the full article: http://journals.royalsociety.org/content/w260687441pp64w5/ Going to the article, look at the numbers for high energy group vs. low energy group, Figure 1 where all their data from their important claims is. Their fundamental measurement (after grouping the people into three seperate groups) was: 108 ± 10.4 boys born of 240 children in the low energy group (45%) 135 ± 11.6 boys born of 241 children in the high energy group (56%) Thus these two groups differ from 50% by 12 boys and 14.5 boys respectively, or in terms of standard deviations 1.2σ and 1.3σ. A difference of 1.3σ or more should be expected in 20% of all studies. That is if they tested for say five variables (like iron intake, potassium intake, etc.) then you would expect one to have to differ from 50% by more than 1.3σ. They report things like giving a χ^2 for linear association between the three data groups, but they ignore the fact that the data points are obviously correlated (the total male/female ratio of all babies born should be ~50% in the total sample; hence if one tertile is high, the others have to be lower. Other faults the article is titled (on all subpages) "preconception diet predicts foetal sex" (which is not what was done ... they found an unpredicted correlation, and haven't used it to make a prediction, which would require a separate group). Now adding in the fact that male's sperm determines the sex, having to come up with convoluted arguments to possibly explain a causation route makes this extremely unlikely. If you think that a females dietary intake changes the chances of a male vs. female foetus actually a baby, can't you first (a) test things like the acidity in a womb on a high energy or high cereal diet, (b) then independently test the survival rate of embryos in the different environments. Or at least do a predictive study. Have couples who do not care about the sex of the child trying to conceive go into family planners, consent to participating in a study and give them high energy (or high cereal diets) and see if any correlation arises.
Well I'm confused now. I have always been acidic. High protein, high energy diet, and an addiction to sugar. Tobacco is acidic and yes unfortunately I have been a smoker. I have always wanted a boy - I have two girls and I am going to be 38 in a couple weeks. Husband will be 35 in a couple months. Now I have read "The Shettles Method" it says that an acidic environment favors girls and an alkaline environment favors boys. This article completely blows that concept. I thought because my body is naturally acidic I'm destined to have girls. I never followed the "Time of Conception" Principle. Having sex prior to my ovulation by 2 to 3 days on through and past ovulation. I believe had we tried to conceive only on ovulation day or the hours after the egg dropped so to speak instead of just rolling around in the hay for days on end, I may have had a boy. So this now brings me back to the original concept that it's a 50/50 crap shoot based on timing, position, x verses y sperm counts, and of course GOD or destiny as some would prefer to call it. There are far to many variables and no matter how much you will it to be one sex or the other - you should just be happy that you have a healthy baby that made it to term. Then you get to spend the rest of your life making sure that your children flourish and survive in this crazy world. So hopefully you'll just relax and have fun while trying to procreate.
Mr. Hopkins, Yes, I figured out your point right after I made my post. Thanks. Interesting story.
I wish Mike Hopkin had explained this "story" better. I agree with James Ledoux about statistical analysis. Sometimes it's not about people don't wanna believe it but the way you prove your findings. At the beginning I was thinking we were like crocodiles about their eggs and temperature and that by chemical and biological features the human fetus could get sex change, totally weird!!