Sticky, translucent strings dangle from Wesley Smith’s chopsticks as the American tourist relishes his nattō, the loved and hated Japanese fermented soybean superfood going global one slimy mouthful at a time.

The latest trade statistics show Japan’s exports of the highly nutritious, gooey beans tripled from 2017 to 5,248 metric tons in 2025, with China and the United States topping the list of destinations. The delicacy infused with beneficial bacteria remains a traditional Japanese breakfast staple, but its pungent aroma, viscous texture and yeasty taste divide even its homeland.

“I thought it was a little funky at first,” Smith says during his recent lunch at Sendaiya, a Tokyo restaurant that serves all-you-can-eat nattō menus — an idea of hell for some people yet heaven for others.

But over the years, the mushy yellow-brown legumes “became an acquired taste like a strong cheese can, because you know how cheese can smell like dirty socks,” the 47-year-old Arizonan says.

Recent years have seen nattō join a series of fermented foods, from kimchi to kombucha, that have surged in popularity worldwide as Americans in particular seek better digestive health following the COVID-19 pandemic. Regular consumption of the high-fiber, protein-packed snack is often linked to stronger immune systems, improved digestion and greater bone density. In China, too, the “trend toward health-consciousness especially among the middle- and upper-income classes” is igniting interest in Japanese foods, the Japan External Trade Organisation said in a recent report.

In Los Angeles at Japanese restaurant Suehiro, owner Kenji Suzuki has noticed more non-Japanese clients taking the plunge.

“When social media started talking about nattō and that it’s a superfood, I think then more and more people wanted to see what it is (and) wanted to taste it — ’Is it as bad as people say it is?’” says Suzuki, the second-generation owner of Suehiro. “Some people maybe don’t like it, but other people, you know, they love it.”

During their lunch in Tokyo, Smith’s wife and fellow tourist Maya Bourdeau, 46, likened nattō to “natural wine” with “that slightly different taste.”

While she vigorously stirred her bowl of bibimbap topped with nattō, Smith knew that this would only make it even stringier.

“Subconsciously, I didn’t want to have nattō just dripping from my beard,” he says, laughing.

Whisking, he says, also “really maximises the sliminess,” which he believes is so off-putting for many Americans that he doubts nattō — for all its recent hype — will ever go mainstream.

“I can’t think of anything in American cooking that’s common with that slimy texture.”

But Daisuke Tsujimoto is all for it, having traveled hundreds of kilometers from Osaka to Tokyo to fill his boots at Sendaiya.

“It really is a food culture Japan can be…