Oysters may excite the libido, but there is nothing like a hearty breakfast laced with sugar to boost a woman's chances of conceiving a son, according to a study released Wednesday.

Likewise, a low-energy diet that skimps on calories, minerals and nutrients is more likely to yield a female of the human species, says the study, published in Proceedings of the Royal Society B: Biological Sciences, Britain's de facto academy of sciences.

Fiona Mathews of the University of Exeter in Britain and colleagues wanted to find out if a woman's diet has an impact on the sex of her offspring.

So they asked 740 first-time mothers who did not know if their unborn foetuses were male or female to provide detailed records of eating habits before and after they became pregnant. The women were split into three groups according to the number calories they consumed per day around the time of conception.

Fifty-six percent of the women in the group with the highest energy intake had sons, compared to 45 percent in the least-well fed cohort.

Beside racking up a higher calorie count, the group who produced more males were also more likely to have eaten a wider range of nutrients, including potassium, calcium and vitamins C, E and B12.

The odds of an XY, or male outcome to a pregnancy also went up sharply "for women who consumed at least one bowl of breakfast cereal daily compared with those who ate less than or equal to one bowl of week," the study reported.

These surprising findings are consistent with a very gradual shift in favor of girls over the last four decades in the sex ratio of newborns, according to the researchers.

Previous research has shown -- despite the rising epidemic in obesity -- a reduction in the average energy uptake in advanced economies. The number of adults who skip breakfast has also increased substantially.

"This research may help to explain why in developed countries, where many young women choose low calorie diets, the proportion of boys is falling," Mathews said.

The study's findings, she added, could point to a "natural mechanism" for gender selection.

The link between a rich diet and male children may have an evolutionary explanation.

For most species, the number of offspring a male can father exceeds the number a female can give birth to. But only if conditions are favorable -- poor quality male specimens may fail to breed at all, whereas females 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," thus contributing to the survival of the species, explains Mathews.

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

While the mechanism is not yet understood, it is known from in vitro fertilisation research that higher levels of glucose, or sugar, encourage the growth and development of male embryos while inhibiting female embryos.

Sex takes 3 to 13 minutes, study says

• Story Highlights
• Survey of sex therapists seeks optimal amount of time for intercourse
  
• Time doesn't count foreplay; 1 to 2 minutes rated too short
  
• 2005 study found median time for sexual intercourse was 7.3 minutes
  
• Researcher hopes to ease minds of those who think they "should last forever"
  

NEW YORK (AP) -- Maybe men had it right all along: It doesn't take long to satisfy a woman in bed.

A survey of sex therapists concluded the optimal amount of time for sexual intercourse was 3 to 13 minutes. The findings, to be published in the May issue of the Journal of Sexual Medicine, strike at the notion that endurance is the key to a great sex life.

If that sounds like good news to you, don't cheer too loudly. The time does not count foreplay, and the therapists did rate sexual intercourse that lasts from 1 to 2 minutes as "too short."

Researcher Eric Corty said he hoped to ease the minds of those who believe "more of something good is better, and if you really want to satisfy your partner, you should last forever."

The questions were not gender-specific, said Corty. But he said prior research has shown men and women want foreplay and sexual intercourse to last longer.

Dr. Irwin Goldstein, editor of the Journal of Sexual Medicine, cited a four-week study of 1,500 couples in 2005 that found the median time for sexual intercourse was 7.3 minutes. (Women in the study were armed with stopwatches.)

It's difficult for both older men and young men to make sexual intercourse last much longer, said Marianne Brandon, a clinical psychologist and director of Wellminds Wellbodies in Annapolis, Maryland.

"There are so many myths in our culture of what other people are doing sexually," Brandon said. "Most people's sex lives are not as exciting as other people think they are."

Fifty members of the Society for Sex Therapy and Research in the U.S. and Canada were surveyed by Corty, an associate professor of psychology at Penn State Erie, The Behrend College, and student Jenay Guardiani. Thirty-four members, or 68 percent, responded, although some said the optimal time depended on the couple.

Corty said he hoped to give an idea of what therapists find to be normal and satisfactory among the couples they see.

"People who read this will say, 'I last five minutes or my partner lasts eight minutes,' and say, 'That's OK,' " he said. "They will relax a little bit."

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Professionals pushing 40 and older are joining the college crowd on the social hub. Can CEO Zuckerberg's team give them reason to stick around?

by Aaron Ricadela

Facebook, the online hangout for college kids and recent graduates, is growing up. The site has amassed an audience of 33 million Web users, initially by catering to well-scrubbed kids who use the social network to nudge their friends, share photos, and swap music tips—all while consuming ads from Gen Y brands like Apple (AAPL), Jeep (DCX), and Red Bull.

Lately, an influx of older users—professionals their 30s and 40s, many in high-tech—is changing the face of Facebook. Among Silicon Valley executives, journalists, and publicists, Facebook has become the place to see and be seen. And it's not just tech. Consulting company Ernst & Young's Facebook network boasts 16,000 members, Citigroup's (C) claims nearly 8,500.

Factor in plans by Microsoft (MSFT), Facebook's biggest business partner, to help turn the site into a tool for making professional connections, and the Palo Alto (Calif.) Internet company could be on the cusp of expanding its already impressive advertising roster, increasing its value as a buyout target or initial public offering candidate, and challenging professional-networking site LinkedIn as the go-to nexus for recruiters and investors.

Changing Traffic Patterns

"People in the Valley definitely search professionally on Facebook first," says Keith Rabois, vice-president of strategy and business development at Slide.com, which makes photo-sharing applications that can be used on other sites, including Facebook. Rabois was an executive at LinkedIn until May.

But older users are behind the recent traffic surge at Facebook, which says it signs up 150,000 new users a day. In June, 11.5 million of the individual visitors to the site were 35 or older, more than double the number a year before, according to market researcher ComScore Media Metrix. The 35-and-up crowd now accounts for more than 41% of all Facebook visitors. Among the fogeys with profiles: Internet pioneer and Google executive Vinton Cerf, venture capitalist Vinod Khosla, and Salesforce.com (CRM) CEO Marc Benioff. Jeff Pulver, a telecom entrepreneur and blogger, famously said in a recent post that he was forsaking LinkedIn for Facebook as his main professional hub (see BusinessWeek.com, 8/6/07, "Confessions of a LinkedIn Dropout").

Even Facebook's competitors acknowledge change is afoot. "Clearly, Facebook has lots of traffic and a lot of that traffic is from the same group of users as on LinkedIn," says David Cowan, a managing partner at Bessemer Venture Partners, a LinkedIn investor (see BusinessWeek.com, 1/29/07, "LinkedIn Reaches Out"). Yet during Facebook's most recent growth spurt—it has added 1.3 million visitors since May, according to ComScore—LinkedIn's audience hasn't declined, Cowan says.

"A Lot More Buzz"

So the question now for Facebook, marketers looking to advertise there, companies that want to own it, and investors who eventually may buy its shares is whether 23-year-old CEO Mark Zuckerberg and his deputies can keep attracting the long-in-the-tooth crowd while preserving the site's spring-break atmosphere of beer-drinking photos and innuendo.

Since its start in 2004, Facebook has attracted a more upscale young audience than News Corp.'s (NWS) MySpace, while avoiding the button-down feel of LinkedIn (see BusinessWeek.com, 7/2/07, "MySpace, Facebook: A Tale of Two Cultures"). "In some ways, LinkedIn feels more like a Chamber of Commerce mixer," says Barry Parr, a media analyst at JupiterResearch. "Facebook clearly has a lot more buzz." More than 48% of Facebook visitors in June came from households with incomes over $75,000, rivaling 55% for LinkedIn, and well above MySpace's 39% figure, according to ComScore.

Advertisers have taken notice. Coca-Cola (KO) has been running promotions on MySpace the past two years for brands including Cherry Coke and Fanta, and has promoted Diet Coke and other drinks on Google's (GOOG) YouTube. The company has yet to advertise with more than simple banners on Facebook but is weighing its first large-scale promotion there. "We see a lot of opportunity there," says Coke spokeswoman Susan Stribling. Procter & Gamble (PG) has advertised Crest toothpaste, Secret deodorant, and Noxema skin-care products on Facebook, and more campaigns are coming in the fall, a spokeswoman says without elaborating.

Most of Facebook's revenue comes from banner ads placed by Microsoft as part of a 2006 deal between the companies. Facebook also directly sells more interactive campaigns, including sponsored profiles and "stories" that appear in users' constantly updated news feed on the site, advertising such things as Hewlett-Packard (HPQ) computers and PNC Bank (PNC) financial services. As the site lures more professionals, it could attract more brand advertisers that want to aim word-of-mouth campaigns at an upscale audience, says Parr. "Facebook is obviously a wonderful environment to reach people in a way that's personal, but not too invasive," he says.

Greasing the Wheels

Today, Facebook's main professional value is "building social capital" among business contacts, says co-founder and vice-president of product engineering, Dustin Moskovitz. He's referring to the informal banter, such as through status updates and games with industry friends on the site, that can grease the wheels for interaction when work needs to get done. Is anyone using Facebook to add new contacts to their Rolodex? "They're certainly doing it with us," says Moskovitz, who says his Facebook inbox is starting to function a lot like traditional e-mail.

Informal interaction could be just step one in Facebook's plans to burnish its professional credentials. Microsoft is helping the company with technology that could turn Facebook's trove of data on members' names, ages, connections, and tastes into directories of users accessible by business software programs. "They may very well be building one of the next interesting collaborative platforms, and it may have business applications as well," says Dan'l Lewin, a corporate vice-president at Microsoft. "They're learning in real time, and the audience is speaking."

In May, Facebook announced that it would let third-party software developers tap into its user data to build miniature software programs that could make the site more useful. So far, the results have been mostly programs such as iLike, which lets users share music preferences, or SuperPoke, whereby users can virtually slap, spank, or pinch pals (see BusinessWeek.com, 5/24/07, "Facebook Aims to Socialize All Online Services"). Microsoft envisions more sober applications: It recently released design software that can let nontechnical users combine Facebook data with elements of other Web sites and blogs like Microsoft's Virtual Earth and Yahoo's Flickr to create new programs.

In the Driver's Seat

Facebook's expanding scope could also increase its market value. Bear Stearns (BSC) analyst Robert Peck estimated in an Aug. 1 report that Facebook could fetch $4.9 billion in an acquisition; he argued that Yahoo! (YHOO) should buy it or another social site to capture Internet ad revenue flowing to such networks. Facebook's revenue could more than double, to $358 million, in 2008 from $140 million in 2007, Peck said.

Facebook has turned down an acquisition offer from Yahoo, and according to reports it also rebuffed Google, Microsoft, and Viacom (VIA). Now, those snubs could look shrewd. In other signs the company is girding for expansion, if not an IPO, in July it hired a new chief financial officer, Gideon Yu, who was CFO at YouTube before the company sold itself to Google. The same month, Facebook hired Chamath Palihapitiya, an investor at venture capital firm Mayfield Fund as vice-president of product marketing and operations.

On July 19, Facebook made its first-ever acquisition, snaring two creators of the open-source Firefox Web browser. Facebook director and early investor Peter Theil said in a recent interview with The Deal that an IPO wouldn't come until 2009 at the earliest. Facebook "is focused on being an independent company," says a spokeswoman, who declined to comment on the prospect of an IPO or make Zuckerberg available for an interview.

Speed Bumps Along the Way

To be sure, Facebook has experienced growing pains. High-profile users say they're starting to get unwanted requests from strangers who try to horn in on their network to ask for favors. Some college-age kids see the influx of users old enough to be their parents as an affront. And a couple of Zuckerberg's old Harvard University classmates sued the company in July for allegedly stealing their ideas. In 2006 the company had to quell complaints from users who said Facebook's broadcast of their every move on the site violated their privacy (see BusinessWeek.com, 9/8/06, "Facebook Learns from Its Fumble").

What's more, Facebook's world of pokes, spanks, and party photos can't hold a candle to LinkedIn's more professional milieu for executives who want to make connections, says Reid Hoffman, LinkedIn's co-founder, chairman, and president. "Many of the bloggers don't really understand the use case for LinkedIn," he says.

Still, Hoffman admits that people are "piling on and taking a look around" Facebook. "If you're going to recruit college students, heck, I'd go to Facebook," he says. Given the flock of older professionals joining the Facebook crowd, before long it won't just be headhunters who have business to do there.

Ricadela is a writer for BusinessWeek.com in Silicon Valley. 

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Emerging data suggest the two may not be direct competitors after all. Businesses that want to reach these audiences have more to learn

by Maha Atal

The blogosphere is buzzing about a provocative June 24 essay by U.C. Berkeley researcher Danah Boyd suggesting that MySpace and Facebook users are dividing along race and class lines. Even as her timely ethnographic observations touch off debate among users and Web developers, they underscore a question businesses have been asking since MySpace first launched: Who really uses these sites and what are they doing there? What can businesses learn from the emerging information about growing audiences on MySpace and Facebook, the largest of the online social-networking sites? We took a look at current data to ascertain who's doing what, where, and how.

One thing's for sure: These networks—and questions—are big. According to comScore, 68 million unique users logged on to MySpace in the last month; 26 million to Facebook. On both networks, adults predominate, but on MySpace, half of the users are age 35 and older, while users age 18-24 make up only 17%. On Facebook, older users make up 40%, with college students (29%) being the next biggest group. MySpace users tilt toward the lower middle classes, Boyd says. ComScore reports that the three lowest income brackets are overrepresented there, whereas on Facebook, the opposite is true: There, the three highest income groups dominate.

Identity and Fantasy

MySpace understandably has been defensive about these income and education differences. A spokesperson says that nearly a quarter (22%) of its users earn more than $100,000. She adds: "The actual numbers according to comScore show that MySpace has a larger percentage of graduate students than Facebook."

One critical distinction between MySpace and Facebook is how users present themselves. Facebook originally flourished in college communities (it was founded by Mark Zuckerberg, then an undergraduate at Harvard), and students needed a ".edu" e-mail address to join the site. As a result, users stuck more closely to their real identities, and their online behavior in terms of manners and expectations tended to mirror their offline behavior. Although Facebook is now open to anyone, that tradition still holds. "On Facebook, you really have to be who you are, so it's more controlled and polite," says Jason Hirschhorn, president of Sling Media Entertainment Group, formerly head of digital media for MTV.

On MySpace, on the other hand, there is an understood degree of fantasy involved. Users reveal who they want to be, through their interests in music or movies, but people aren't always who they say they are. Says Jeff Jarvis of popular media blog BuzzMachine.com: "Facebook brings elegant organization to real identities and communities people already have. MySpace is a gussied-up personal Web page, and it's about new publishing forms and mediums." If Facebook users are displaying their real-world relationships, MySpace users are self-promoters, concerned with making new connections through exaggerated, even fictionalized, personas.

Different Purposes

Boyd's research and the sites' contrasting cultures suggest that although both networks are open to the public, they may not be direct competitors. "The press is saying MySpace is going out of business; everyone's switching to Facebook," says Boyd, but really, "they're hitting different audiences."

In truth, the same audiences are patronizing both networks—comScore reports a 64% overlap—but they are using the sites for different ends. MySpace helps users showcase their interests in music or film, find new artists to follow, and meet others with similar tastes. Facebook begins with relationships, rather than content, helping users keep in touch with friends from college or professional colleagues. "A lot of young users find that MySpace and Facebook can serve distinct functions in their lives," says Siva Vaidhyanathan, a cultural studies professor at New York University. "Facebook and MySpace are achieving something close to an identity and a niche that can allow both of them to thrive."

For businesses, then, both networks continue to merit investment for different reasons. For consumer-products companies targeting younger audiences or entertainment companies, MySpace seems like the obvious best bet. According to MySpace, entertainment giants Sony (SNE), 20th Century Fox, and Warner Bros. (TWX) are among its top advertisers. "When it comes to discovering bands, promoting music, MySpace is still the place," says Vaidhyanathan.

Attractive Minimalism

But Facebook's minimalist approach to features can also be attractive to companies. While MySpace has its own media players and formats to which companies simply upload content, Facebook allows users and companies to build multimedia applications. Travel companies, such as SideStep.com, have built interactive maps allowing users to share vacation ideas. The Washington Post's (WPO) Compass application allows users to share political beliefs. "Facebook is very Web 2.0," says Hirschhorn. "It is the 'unbrand' and it allows users to pick the best features and companies to showcase their own brands."

Advertisers continue to pour their dollars into MySpace, where a more traditional banner-advertising approach still applies. Google (GOOG), for example, paid $900 million in August, 2006, for the right to put Google ads on the site. "Facebook's been pretty limited to a niche market," says Peter Gardiner, partner and chief marketing officer at advertising agency Deutsch (IPG). "But the audience is going to change dramatically," now that membership is open to the general public.

As these networks continue to evolve, the demographic divides noted by Boyd may give way to new distinctions. Our understanding of who the users are and how they use the sites is also on the rise as research companies are cropping up to help businesses measure and interpret online behavior. Now businesses need to turn that growing understanding into smart strategies for communicating with their customers.

Maha Atal is an intern at BusinessWeek.

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People with migraines also may be suffering from some brain damage as brain cells swell and become starved of oxygen -- a finding that may help explain why migraine sufferers have a higher risk of stroke, researchers reported on Sunday.

Similar brain damage can occur with concussions and after strokes, the researchers said in this week's issue of the journal Nature Neuroscience.

They said their findings suggest that migraine sufferers should not simply get pain relief but should take drugs that prevent the migraine, which is often preceded by "aura" -- a series of visual disturbances that can include flashes of light or black spots.

The research, which was done in mice, also suggests giving oxygen may help reduce the damage, said Takahiro Takano, Maiken Nedergaard and colleagues at the University of Rochester in New York, working with a team at the Danish pharmaceutical group Novo Nordisk.

They studied a process called cortical spreading depression, known as CSD, a wave of changes in cells associated with migraine, stroke and head trauma.

They used a precise two-photon microscopic and oxygen sensor microelectrodes to look at the brains of live mice while they caused this process.

They saw a swelling occur and the brain cells became starved of oxygen. The nerve cells were damaged -- specifically the dendrites, the long, thin spikes that stretch from one nerve cell to another.

28 MILLION SUFFERERS IN U.S.

"This observation may have direct clinical implications, as several lines of work support the notion that cortical spreading depression constitutes the neurological basis of migraine with aura, and spontaneous waves of CSD may contribute to secondary injury in stroke and traumatic brain injury," the researchers wrote.

Migraine is a severe and debilitating form of headache, affecting 28 million people in the United States alone.

Two studies, including one published last week in the Archives in Internal Medicine, show that people who have migraines are more likely to have heart attacks.

A 2004 study in the British Medical Journal found that migraine sufferers are twice as likely to suffer a stroke as people who do not have the headaches.

Women are much more likely to suffer the characteristic pain of a migraine.

Usual pain medication often has little effect on migraine but a class of drugs called triptans, also called serotonin agonists, and ergotamine drugs, can be used to prevent the worst effects if patients take them at the first sign.

Giving the mice rich doses of oxygen seemed to shorten the duration of the wave of brain effects seen in CSD, the researchers said. They noted that migraine and cluster headache patients are sometimes treated with high-pressure oxygen.

It is not clear if the effects of migraine are permanent, the researchers said. Some studies have suggested they are while others have shown no difference in memory and other cognitive effects in migraine patients.