Breakfasting for Baby Boys

The headline said that better nutrition meant a greater likelihood of having boys. The first paragraph mentioned a nutritious breakfast. I didn't try to track down the original paper, or even finish the story.

But I predict that the effect is small. Why? Because the natural sex ratio (without abortion for sex selection) is only from 1.03 to 1.06 boys to girls. If a nutritious breakfast meant (for instance) 50% more boys, I'd expect the ratio in developed countries to be more like 1.2-1.3 (not everybody chooses to eat wisely).

So, let's unseal the box and read the story: From the BBC:

The study focused on 740 first-time pregnant mothers in the UK, who were asked to provide records of their eating habits before and during the early stages of pregnancy.

The researchers found 56% of women with the highest energy intake around the time of conception had boys, compared to just 45% among women with the lowest energy intake.

That's more like a 20% effect, but look at the statistics. If they broke the group into thirds (more probably 5ths, but never mind that) then the highest group has 230 members, with an excess of 14 in the top group and deficit of 12 in the bottom group. This isn't a 3-sigma effect. I don't believe 20%. 10% maybe, though I'd want to see corroboration.

The article says there's been a decrease in breakfast caloric intake in the developed world. Hmm. Not what I'd have expected.

At any rate, the effect is still small enough to disappoint women trying influence the sex of their babies.