Fiona Matthews of the University of Exeter is the lead author of a tantalizing new study showing that mothers who eat more and eat better around conception are more likely to have boys. The mother's diet does not change the sex of developing embryos, but does seem to affect whether male embryos implant and develop.
Eating breakfast cereal seemed to be one of the stand-out correlates of having more boys. There has been a steady drop in the number of boys born in industrialized countries, which correlates with more women skipping breakfast and eating low-calorie diets.
This study is based on correlations. No one knows exactly why it works. I expect this finding will be kicked around a dozen times by contradictory follow-up studies. This is as it should be -- that is how science advances.
In the meantime, moms who want a son should stock up on oatmeal.