BELEM, Brazil — Long before the Portuguese colonized Brazil, the oily purple berry of the acai palm tree was a staple of native Amazon cuisine, with locals drinking its thick juice alongside fried river fish or sprinkled with toasted manioc flour.

Virtually unknown outside this remote corner of Latin America's largest nation until 15 years ago, acai juice suddenly is a global "super food," riding high on claims it fights cholesterol, is an anti-aging elixir and even acts as a natural Viagra.

But skyrocketing demand has jacked up the price of acai where it's most loved, in Belem, the epicenter of the acai trade. The city's 1.3 million residents consume an estimated 200,000 liters of acai each day, making it more popular than milk.

A few years ago, a liter of acai (pronounced AH-sigh-ee) juice cost 52 cents. Today it's $2.60. In an area where monthly income often is less than $200, that price puts it out of reach for many of the people for whom acai is as much a culture as a beverage.

"If I buy acai for lunch, I can't have it for dinner. If I buy it for dinner, I can't have it for lunch," says Santana Wanderlei Pereira Diniz, a 40-year-old mother of five who has only mixed success offering her children other juices. "It's just too expensive."

Even in Brazil, acai wasn't known much beyond Belem until the early 1990s. Because the fruit's juice spoils after about 24 hours, it couldn't be shipped outside the region.

But then acai producers figured out a way to freeze the pulp, allowing it to be sent to Brazil's populous south.

Because freezing robs acai of much of its subtle flavor, producers spiked it with guarana syrup (derived from another Amazon berry, this one with a punch akin to caffeine), helping the drink catch on in the rest of the country.

Today, the blend — packed with vitamins, minerals, antioxidants, amino acids and healthy omega fats — is a staple at juice bars in Rio de Janeiro and Sao Paulo, where health enthusiasts use spoons to attack bowls piled high with the dark purple slush — the result when the thick frozen pulp is run through the blender.

WIDESPREAD APPEAL

While the acai-guarana mix tastes vaguely of chocolate with red wine and blueberry, the fresh acai juice available only in the Amazon has a fatty, somewhat sour taste trailing off with hints of cinnamon.

Most of the international demand has been fueled by Sambazon Inc., which is based in San Clemente, Calif. The company was founded by Ryan and Jeremy Black, of Northport Beach, Calif., who tried acai during a 1999 surfing trip to Brazil.

Today, the company says it handles about 80 percent of the acai exported to the U.S. — pulping 100 metric tons a day at its plant in Amapa, across the Amazon from Belem. The company expects to export around 4,000 metric tons this year alone.

Now the juice is common in natural foods stores — available in juices, smoothies, even freezer packets — in the U.S., England and Japan under brand names like MonaVie, Bossa Nova, Zola and Sambazon.

Coca-Cola has entered into a distribution agreement with Los Angeles-based Bossa Nova brand acai juices, and Anheuser-Busch adds the fruit to its new energy drink, 180 Blue. Proctor & Gamble Co. even puts it into their Herbal Essences shampoo. Starbucks has a new acai smoothie.

According to Spins Inc., which tracks natural foods, sales of acai products in the U.S. were $14 million for the 12-month period ending in April, up from $2.7 million for the same period two years before.

But back in the Amazonian state of Para where Belem is the capital, acai prices have jumped 60 percent over last year, says Roberto Sena, technical coordinator for Diesse, a trade union group.

Locals still find ways to obtain the fruit, buying lower quality juice or sacrificing other foods. For many, acai with manioc flour (a staple of Brazilian cuisine, made by toasting and grinding manioc — a tuber similar to the potato) is all they eat for lunch and often dinner, as well.

"Acai is an addiction," says Adaladio Correio Santos, who has been buying and selling it for 40 years. "If someone can't eat acai, they complain there's an empty space in their stomach, even if they've just ate a full meal. They say without acai, nothing fills them up."

Throughout stiflingly hot Belem, little red signs advertise sparse storefronts that contain little more than the stainless-steel machine used to pulp the fruit and a refrigerator where the juice is stored for sale in plastic bags.

And each morning in the port, hundreds of wooden-hulled river boats converge on a teeming open air market just to the side of the Ver-O-Peso — or See the Weight — market, a crumbling baroque structure resembling a colonial-era train station.

Here, hundreds of men lug woven baskets filled with the dark, shiny fruit plucked from the 80-foot-high palm trees that line the river islands spilling out toward the Atlantic. Almost all the acai palms grow wild like weeds in deforested flood plains.

Each basket yields about 8 liters of juice and costs about $13.40. During the dry season, when the fruit is plentiful, the price can drop to $4.12. Researchers, however, say seasonal price variations may be a thing of the past.

"In the past the price was regulated by the seasons," says Samuel Almeida, a researcher specializing in acai at the Goeldi Museum, a scientific institute in Belem. Previously, the dry season of August to December meant plentiful acai and lower prices.

"Now the price doesn't drop because the big companies have to buy all their acai when it is plentiful and freeze it so they have stock all year around," Almeida says.

DEMAND RAISES COSTS

While increased demand and higher prices has been a boon for producers and exporters, middlemen and the vendors who traditionally sell acai in poor neighborhoods are getting squeezed out along with the local consumer.

Ryan Black says the company works hard to be a model of corporate responsibility, making sure acai is sustainably harvested in a part of Brazil where farmers often slash and burn the rainforest to make way for cattle and soy plantations.

Sambazon buys directly from the growers associations and has hired researchers to study whether increasing demand is causing farmers to cut down forest to make way for acai trees. So far, Black says, there's no evidence of that happening.

But he says there's plenty of room for acai producers to harvest more fruit naturally. Sambazon estimates that only 5 percent to 10 percent of the acai that grows in the forest ends up being consumed. The rest, Black says, falls to the ground and rots.

While Black says the acai boom is good for the economy in the Amazon, he conceded that there's no way to avoid higher local prices with the globalization of the fruit.

"I know that certainly the price of acai is going up where the demand is," he says. "I think that's fairly natural that as demand increases and supply goes down the price goes up."