Actress Whitney Cummings first heard about açaí last year when she was shooting an episode of HBO’s Tell Me You Love Me. On the set was a catering truck that served nothing but açaí bowls: a mixture of bananas, granola, and açaí sorbet. Now Cummings buys açaí in bulk. “Maybe this is psychosomatic, but since I’ve been into açaí, I feel like I have a lot of energy,” says Cummings, 25. “Pomegranate juice is too tart for me, and goji juice is too bitter. Don’t get me started on wheatgrass.”

Hollywood’s health-conscious jet-setters are waking up and buying their açaí—a berry imported from Brazil that is being touted for its antioxidants. Too bitter to eat on its own, the fruit is sold as frozen pulp at Whole Foods and other natural-food stores and is being mixed into everything from energy drinks to shampoo. According to açaí distributors, actress Salma Hayek, who takes her açaí in smoothies, is a convert; so are Matt Damon, Paul McCartney, and surfing celeb Kelly Slater, who sings the fruit’s praises in a YouTube video. (View an interactive feature showing the berry's trip from the tree to the grocer.)

While few studies have looked into its actual health benefits (the Food and Drug Administration doesn’t regulate such claims), açaí is booming as a fitness ingredient. In the past year, sales of açaí products have more than tripled, to $66 million, according to SpinScan, a natural-products research group, and billion-dollar players like Coca-Cola are experimenting with açaí. In 2006 Anheuser-Busch launched 180 Blue, an açaí-fortified energy drink, and last year Procter & Gamble began infusing some of its hair products with açaí.

It is a surprising turn of events for brothers Jeremy and Ryan Black, who are credited with starting the craze back in 1999. After a trip to Brazil, where the Blacks first encountered the berry, they learned that a book by a Belgian scientist proclaimed açaí’s antioxidant powers. They had parts of the work trans­lated and açaí pulp tested. Shortly there­af­ter, they launched the import company Sambazon and began promoting açaí as a source of anti­oxidants. As the company grew—last year, sales hit $15 million—the Blacks brought in new in­vestors, including Stonyfield Farms and MTV co-founder Bob Pittman, now a venture capitalist.

But growth has its challenges. For one, the cost of raw açaí has more than doubled since 2003; the berry now retails for about $6 a pound. The Blacks have also tangled with rivals, suing one competitor over marketing language in 2003. (The case was settled.) Now Jeremy complains that newcomers are uneducated about the fruit and points to a recent Tropicana commercial. “They mispronounce açaí. It’s pretty funny to us to hear that. We don’t know if they did that on purpose or they just didn’t know. For the record—and ask any Brazilian—it’s ah-sigh-ee. Not a-kai, not a-sigh.”