Page last updated at 23:12 GMT, Tuesday, 22 April 2008 00:12 UK

High-calorie diet linked to boys

Do regular breakfasts boost baby boy numbers? Christine McGourty reports

A woman's diet around the time of conception may influence the gender of her baby, research suggests.

The study suggests a high-calorie diet at this time - and regular breakfasts - might increase the odds of a boy.

The researchers say the modern trend to opt for low calorie diets might explain why the proportion of boys is falling in developed countries.

The study, by the Universities of Exeter and Oxford, appears in the Royal Society journal Biological Sciences.

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.

If a mother has plentiful resources then it can make sense to invest in producing a son because he is likely to produce more grandchildren than would a daughter
Dr Fiona Mathews
University of Exeter

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.

The average calorie intake for women who had sons was 2,413 a day, compared to 2,283 calories a day for women who had girls.

Women who had sons were also more likely to have eaten a higher quantity and wider range of nutrients, including potassium, calcium and vitamins C, E and B12.

They were also more likely to have eaten breakfast cereals.

Fewer boys

Over the last 40 years there has been a small but consistent decline, of about one per 1,000 births annually, in the proportion of boys being born in industrialised countries, including the UK.

Previous research has also shown a reduction in the average energy intake in the developed world, and there is also evidence that more people now skip breakfast.

Scientists already know that in many animals, more males are produced when a mother has plentiful resources or is high ranking.

The phenomenon has been most extensively studied in invertebrates, but is also seen in horses, cows and some species of deer.

The explanation is thought to lie with the evolutionary drive to produce descendants.

Lead researcher Dr Fiona Mathews said: "Potentially, males of most species can father more offspring than females, but this can be strongly influenced by the size or social status of the male, with poor quality males failing to breed at all.

I would urge women to not to start starving themselves in order to try influence the sex of their baby
Dr Allan Pacey
University of Sheffield

"Females, on the other hand, reproduce more consistently.

"If a mother has plentiful resources then it can make sense to invest in producing a son because he is likely to produce more grandchildren than would a daughter.

"However, in leaner times having a daughter is a safer bet."

Glucose levels

It is known from IVF research that high levels of glucose encourage the growth and development of male embryos while inhibiting female embryos.

In humans, skipping breakfast depresses glucose levels and so may be interpreted by the body as indicating poor environmental conditions and low food availability.

Dr Allan Pacey, an expert in fertility at the University of Sheffield, said there was good evidence that nature had subtle ways of changing the sex ratio of a population in response to a variety of circumstances.

However, he said: "I would urge women to not to start starving themselves in order to try influence the sex of their baby.

"It has been observed in some animal studies that even small changes in female diet can affect the life long health of the offspring, so it is important that the mother has appropriate nutrition at the time of conception and throughout her pregnancy."

Here are some of your comments on this story:

I will definitely use this research to try and influence my child to be a boy! Even if it doesn't work, I suppose it's worth a try...If only Henry the VIII knew about this.
Christina Villalobos, Deerfield Beach FL USA

I am 23 weeks pregnant expecting twins, a girl and a boy. I'm interested to see how the study could explain this!
Stephanie, Yeovil, UK

Very interesting. I was on a very, very strict low GI diet (hence low glucose levels?) at the time that I conceived my daughter because I'd been diagnosed with PCOS and my doctor thought I could restart my cycles by losing a stone as I was about a stone overweight. I chose the low GI diet as it is recommended for PCOS. I lost a stone over about six weeks and then got pregnant, although I did take vitamin supplements and I ate very healthily. I was eating more normally when I conceived my son two years later.
Georgina, London

I have recently given birth to a son and craved breakfast cereal and carbohydrates in general throughout my pregnancy. May be something to be said for that...
Laura, Devon

Hold on, back at school (20 years ago) I was told that the male was the one that decided the sex as the female has the XX chromosome and the male has XY. If the X from the male went across a female was produced and if the Y went across a male was produced. Unless the science has changed, how can a female's diet affect the sex of her baby if the male passes on the deciding chromosome.
Leon, Goldcoast

This finding makes perfect sense. It's well known in the animal kingdom that offspring sex can be influenced by the diet of the mother (for example miscarriage of the unwanted sex embryo). In zoology lectures they were always very cautious to not apply findings in animals to humans but in many cases it makes sense and this study I think supports this. I will definately be considering my diet when I plan to have a baby.
Rebecca, Bristol

At present I am pregnant with my fourth son and I have to say my diet is nothing like what they suggest. I never eat breakfast and don't eat a high calorie diet. I think it's purely down to the luck of the draw on whether you have a boy or girl.
Laura, Mid Glamorgan, S Wales

I am 46 years old and have always eaten breakfast cereal first thing in the morning, it's like a ritual. Can't start the day until I have had my breakfast. I had five children (in the space of seven years).The first four were all boys and my last a girl. So maybe there is some truth in this theory. As for high calorie diet, I didn't always watch what I ate, however did not put on weight. Must have been all the running around after the children.
Elizabeth McMullan, Bangor, Northern Ireland

Can you influence a baby's sex?
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