Poor Brazilians are suffering behind what some view was an endorsement by one of the world's most powerful women, activists say.

As has been the case with everything from books to presidential candidates, Oprah Winfrey says she only tasted Acai Berry one time on her show and now the fruit, known for its nutritional value, has enjoyed a huge popularity boost.

The acai fruit, which grows in Amazon jungles, is part of a recent American health craze among those who seek the berry for its supposed benefits to the blood.

But increased demand for acai, say humanitarian activists, has deprived many Brazilians who dwell in the rainforest and eat the fruit for sustenance.

Acai sales reportedly doubled to about $104 million in 2008. Even in the retail market, activists claim, the berry's increased popularity makes it hard for low-income customers to buy.

 A UCLA study shows that acai has less anti-oxidant fuel than red wine, grape juice and other products more commonly found in urban regions.

On Friday, Oprah sent a tweet that read, "BUYER BEWARE: I have NOTHING to do with acai berry scams on internet.