By SETH KUGEL

CAMETA, Brazil - Virtually unknown outside the Amazon two decades ago, and until 2000 not exported from Brazil - its major producer - acai is now an international celebrity, riding the wave of the antioxidant craze and rain-forest chic. On the beaches of Rio de Janeiro, surfers seeking an energy boost spoon acai smoothies from bowls. In the United States, companies touting its antioxidant powers blend the fruit into Snapple red tea, and everything from dietary supplements to beauty products.

But for families who live here along the winding rivers at the hub of acai production, the fruit has long been a vital part of their diet, a cheap way to fill up and a taste of home. And now, for some, it is a source of newfound prosperity.

In places like Cameta, a town of about 117,000, and Belem, the capital of Para State, a bowl of acai pulp is a filling side dish especially valued by poorer families. Although acai smoothies are rare in Para, deep purple acai is a popular flavor at two big ice cream chains based in Belem, Cairu and Ice Bode . You can also find acai candy in gift shops and acai tarts in bakeries.

Sugar is an issue, though. Many locals insist it should never be added to the fruit .

The velvety texture of the thicker varieties is wonderful, but the taste is more - how to put this? - earthy. O.K., it tastes like dirt.

But visitors who hold back on the sugar will find a more complex flavor that, while it remains grassy and earthy, is also fresher and purer than acai that’s been pasteurized, frozen and subjected to the corrupting influences of, say, bananas or granola.

While the old ways of eating acai continue in the Amazon, increased demand elsewhere in the world has driven up prices and made life easier for people like 53-year-old Orisvaldo Ferreira de Souza .

The de Souzas live in a battered wooden home on stilts on Itanduba Island, about an hour by boat from Cameta’s town center. Like the families who live up and down the river from them, they make much of their living off the acai harvest from what they calculate is 8,000 acai palms on 14 hectares.

“Two or three years ago, we had a lot of trouble selling the product,” Mr. de Souza said. “We had to bring it to town, and sometimes we came back without selling it.”

But now, the harvesters don’t even have to leave their land: buyers ply the river right up to their rickety wooden pier offering 10 reais or more. “Just yesterday, six buyers came by,” he said. “We sold 10 baskets each to two of them.”

Ivan Saiki, director of Cam-ta, a cooperative and fruit processor in Tome-Acu, another major acaiproducing municipality, said: “Before the boom, the harvest came and the acai was worth practically nothing. Before, nobody had television, nobody had a motorized canoe. Now many have their own electricity at home. It’s greatly improved the life of the river communities.”