Is Tahitian Noni Juice, the main product of Utah-based Tahitian Noni International, too good to be true? Can the juice, made with a fruit grown in Tahiti, really heal broken bones, kill cancer cells and calm anxious horses?

"The public is buying into this, and it's a real shame," says Will McClatchey, an ethnobotanist at the University of Hawaii who has studied juice from the noni plant for more than 10 years. "It needs to be based on some science, and it's not."

The University of Hawaii Cancer Research Center has been conducting human trials using capsules of powdered noni extract since 2001.

While there have been no adverse effects on patients, researchers haven't found any positive reactions that can be directly attributed to consumption of noni, said Dr. Brian Issell, director of clinical trials at the center.

"Basically, we have no idea what it does," McClatchey says. "I've studied it for years and found nothing."

Tahitian Noni International claims the noni fruit contains an enzyme called xeronine. Dr. Ralph Heineke, a scientist who used to work for Dole studying pineapples, said he discovered the enzyme.

What the enzyme does is unclear, but TNI says the juice helps the body fight disease and infection, increases energy levels and helps cells absorb more nutrients.

But McClatchey says there is no such thing as xeronine.

"It's bogus, it's made-up words," he says. "I'll stake my reputation on it."

McClatchey also says the folks at TNI exaggerate how important the fruit was to early native Polynesians. In his own research, he has found that the fruit was rarely used. The leaves and branches of the noni tree were more popular.

Andre Peterson, TNI spokesman, says the company does not deceive the public about what the juice does.

Under the Dietary Supplement Health and Education Act, nutritional-supplement companies are not allowed to make disease claims. In 1998, TNI was investigated and fined by the attorneys general of several states for making such claims.

Since then, TNI has stopped making such claims and spent thousands educating distributors about what they can and can't say. Distributors who continue to make claims despite warnings from the company are terminated, Peterson says.

Peterson said the company rejects the idea that the juice has no medicinal value.

"It is preposterous to think that people would buy and drink our juice for any other reason than the fact that they feel a benefit in doing so," he said.