XanGo Super Fruit in the Herald Tribune

On stage at a sales convention, XanGo executive Joseph Morton said that when he first stumbled across mangosteen, a tropical fruit with purported curative powers, "I didn't have to have it confirmed in the New England medical journal before I would listen."

The multilevel marketing company has built a huge business around its mangosteen-based juice, which it promotes as an immunity booster. The company still hasn't proved its health benefits - which it says could include a stronger immune system and improved joint function - to skeptical experts. XanGo's Web site includes a disclaimer, noting the juice is not meant to treat or prevent disease. A lab test arranged by The Associated Press found its antioxidant power to be on par with other fruit juices.

Morton, a 37-year-old triathlete nicknamed Ironman Joe, was on a business trip in Malaysia when he saw mangosteen, a white delicacy wrapped in a blood-red leathery shell, on the dessert menu.

From that introduction, Morton, the company's president of international and distributor relations, capitalized on a new brand category of liquid "super-fruits" that is "doing gangbusters," said Jeff Hilton, a partner at Integrated Marketing Group, a branding and packaging consultant.

XanGo has more than two dozen competitors that sell fruit juices, powdered drinks and vitamin fizz tablets. Tahitian Noni International Inc. sold $2 billion (€1.38 billion) worth of noni juice, from the French Polynesia fruit, in its first 10 years by 2006. MonaVie, also of Utah, bottles a blend of acai juice from the Amazon basin berry. Pure Fruit Technologies Inc. underprices XanGo on a mangosteen-based juice that sells in health food stores.