THIS WEEK

10 | NewScientist | 3 August 2013

Japan quake boosts number of female birthsHERE come the girls. Fewer boys than girls were born in the months after the huge earthquake struck Japan in March 2011.

Ralph Catalano of the University of California in Berkeley and colleagues examined hospital records of births in Japan between 2006 and the end of 2011. After the quake, births in areas closest to the epicentre were more

likely to be girls, but provinces farther out showed no gender bias. About 2.2 per cent fewer boys were born in the most damaged areas than expected (American Journal of Human Biology, doi.org/nbj).

It is not the first time such a skew has been noted: fewer boys were born after the US stock market crash of 2008, for instance. The reason may be evolutionary, says Catalano. Boys are more likely to be premature and suffer problems associated with low birth weight than girls. In times of stress, it may therefore be beneficial for the mother to give birth to a girl.

However, it is unclear whether stress causes mothers to miscarry more males or whether fewer males are conceived. Earthquakes provide a natural test for this, Catalano says. If births immediately after show a gender skew, it would suggest that stress is triggering miscarriages. A bias nine months later indicates fewer male conceptions.

The team found evidence for both.

Several mechanisms may be at work, says Catalano. Fetuses produce a hormone called human chorionic gonadotropin, which camouflages them from the mother’s immune system. Weak male fetuses make less of this hormone, meaning they may be at greater risk of attack.

William James of University College London believes the father’s testosterone level plays a role. During periods of high stress, he says, men produce less testosterone, which can reduce the number and quality of the “male” sperm, which carry a Y sex chromosome. Sara Reardon n

“During high stress, men produce less testosterone, which reduces the quality of male sperm”

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Food stamps could help US trim obesity epidemic

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“WITHoUT food stamps I could not eat,” says Thadd Evans. He has a master’s degree in fine art and lives in San Francisco, one of the wealthiest cities in the US. but in March, Evans was laid off from his job making calls for a market research firm, and it is tough for a 62-year-old to find work.

congressional wrangling over legislation to renew funding for the federal Supplemental Nutrition assistance Program (SNaP), which runs out on 30 September, seems likely to result in deep cuts to a scheme that helps feed 46 million US citizens. Some of the rhetoric condemns SNaP as one of many examples of government waste responsible for dragging the US economy into the mire.

In fact, research by the US Department of agriculture (USDa) suggests that SNaP stimulates as much as $9 of economic activity for every $5 it spends. What’s more, public health advocates say the political acrimony has obscured a big opportunity: using SNaP to experiment with solutions to the wider problems of poor nutrition and obesity in the US.

because junk food is cheaper than fruit and vegetables, poverty and obesity often go hand-in-hand.

but, perplexingly, even after controlling for this association, some research suggests that the recipients of food stamps are slightly more likely to be obese.

The US’s obesity epidemic extends far beyond the confines of SNaP, but clearly there is scope for experimenting with the way in

which benefits are delivered to improve the health of the country’s poorest citizens.

a pilot project delivered promising results last month. over 14 months ending last December, 7500 households receiving food stamps in Hampden, Massachusetts, were given an extra 30 cents for every dollar spent on fruit and vegetables. Surveys carried out four to six months

into the study show that consumption of fruit and vegetables was 25 per cent higher in these households than in those receiving regular food stamps.

according to economic models run by Sanjay basu of Stanford University in california, banning food-stamp purchases of unhealthy foods or increasing their price should be even more effective (Medical Decision Making, doi.org/nbf).

The idea of restricting people’s choice is controversial, though, and the USDa, which backed the Hampden study, has so far turned down requests to experiment with restricting junk food purchases. Still, recipients of food stamps seem open to the idea. In another survey last year, just over half of food stamp recipients said that they would support removing benefits for sugary drinks (Public Health Nutrition, doi.org/nbg).

Results like this make public-health researchers optimistic that SNaP could become a vehicle for testing solutions to the US’s collective weight problem and lead to a healthier future for the entire nation. “We can solve this,” says Hilary Seligman of the University of california, San Francisco, who studies the links between food insecurity and chronic disease. “It only takes political will and resources.”

Right now, however, those two things seem to be in short supply where it matters most – in the corridors of power in Washington Dc. Peter Aldhous n

What incentives will make people opt for healthier choices?

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