Q. Can Tahitian noni juice help control my diabetes?

A. Tahitian noni juice comes from the fruit of Morinda citrifolia, a plant native to the South Pacific and Hawai'i. Noni has been used as folk medicine by Polynesians for at least 1,500 years. Rather than the juice, it was the leaves, bark and roots of the plant that were used medicinally.

There are no published studies showing a link between drinking Tahitian noni juice and improvement of diabetes in humans. For diabetes control, traditional uses involved chewing the leaves alone or in combination with other parts of the plant.

It is thought that the soluble fiber in the plant might slow the body's absorption of sugars and slightly reduce blood glucose after a meal. Soluble fiber in other foods has this effect; however, it is unlikely that a significant amount of this fiber is present in noni juice.

A February 2007 report in the Journal of Wound Care concluded that noni juice decreased blood sugar and hastened wound healing in rats. However, the rats in the study were not technically diabetic. Their high blood sugars were induced by medication. Whether this research translates to humans with diabetes is a big leap.

Noni juice is high in sugar. This could potentially aggravate a person's diabetes.

Noni juice is also high in potassium. This may pose problems for people who must restrict potassium intake. This includes people with chronic kidney disease and those who take potassium-sparing blood pressure medications.

People with pre-existing liver conditions or those using medications that may harm the liver are advised against drinking noni juice. There are some reports of liver problems linked to noni intake in this group. In most cases, the problems stopped when noni was discontinued.

When it comes to noni, you name it, they've claimed it. Proponents have claimed that noni can cure diabetes, HIV, cancer, asthma, arthritis, senility and many other health problems. These claims are unproven. Due to Food and Drug Administration actions, some companies have stopped making these unproven claims. Even so, these claims are still widely available on the Internet.

Although a few test tube and animal studies look promising, human studies are just beginning. Researchers may find some benefits to humans in the future. For now, I cannot recommend that noni be used alone to treat diabetes, cancer or any serious illness.

Amy Tousman is a registered dietitian and certified diabetes educator with Nutrition Unlimited in Kailua. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.