Oz, who is also a Columbia University heart surgeon, had frequently mentioned the vitamin-packed berry on his show, but he told ABCNews.com last year that he had never officially endorsed acai.
"Acai is a powerful antioxidant," said Oz, who was in production for his show at press time. "Colorful, dark foods like red wine, pomegranates, concord grapes, blueberries -- they call them brain berries -- are full of nutrients."
As far as those weight-loss properties, Oz said, "I'd be surprised if by itself acai could help."
The BBB warned consumers last year that many companies under scrutiny had used unauthorized images of celebrities to promote their products, claiming falsely that their products can protect one's health and help with weight loss.
The BBB said online sales of acai berry products had mislead consumers, resulting in 10,000 complaints in the last two years.
"The problem was so bad that one company selling these supplements, FWM Laboratories, was actually in the top five for most-complained-about businesses in North America," said Southwick. "In fact, only three companies received more complaints than FWM last year."
"These companies know that people trust Oprah and Dr. Oz and an endorsement from either would be a boon for sales," she said. "Many people in their complaint actually said that they thought they could trust the company because Oprah or Dr Oz endorsed the product."
In a scheme called "negative option" advertising, dozens of companies nationwide offer "free" trials of acai diet products, claiming endorsements from Oprah Winfrey, Rachael Ray and others, but then charge month after month unless the consumer cancels the order, according to the bureau.
"BBB [the Better Business Bureau] can't speak to the restorative or weight loss properties of acai-based products, but we are taking companies to task for their misleading sales and marketing practices," bureau spokesman Steve Cox said at the time.
The endorsements are also misleading, according to the bureau, and some celebrity lawyers have already gone after these online companies.
"Consumers should be aware that Oprah Winfrey is not associated with nor does she endorse any acai berry product or online solicitation of such products. Attorneys for Harpo are pursuing any companies that claim such an affiliation," Don Halcombe, spokesman for Harpo Productions, Winfrey's production company, told ABCNews.com last year.
The so-called "super food" has been praised for its antioxidant properties on television shows and on social networking sites, with some claiming it fights cancer, aging and weight gain.
Today billion-dollar beverage giants, including Coca-Cola Co., PepsiCo Inc. and Anheuser-Busch Cos., are adding the fruit to their beverage lineups, according to The Wall Street Journal. It's also found in products from Stonyfield Farm and Haagen-Dazs. Procter & Gamble Co. recently infused acai into its Herbal Essence shampoos and conditioners.
In November, according to the bureau, more than 1.5 million people searched for the term "acai" on Google. Online ads and Web sites often include a photo of a celebrity -- such as Winfrey -- and falsely claim that she endorses the acai as a weight loss miracle.