The U.S. Food And Drug Administration (FDA) has issued a warning to Hain Celestial Group Inc about a potentially unsafe herb used in some of its herbal teas, saying it might be dangerous to blood sugar, reproductive, cardiovascular and renal systems.

The FDA sent a letter to Hain dated August 17, and named the herb, a natural sweetener made from a South American herb called stevia, as an unsafe food additive. The agency released the letter on its Web site on Tuesday. Stevia is being eyed by big beverage makers looking for new low-calorie sweeteners. In May, Coca-Cola Co and Cargill Inc said they would work together to market the new sweetener, despite the lack of FDA approval. Stevia has been approved in a dozen other countries including Japan, China and Brazil. The FDA letter said that although it has received requests to use stevia in food, data and information necessary to support the safe use have been lacking.

Enzyme from tea could build cancer buffer

Results of an early phase clinical study released in August by the Arizona Cancer Center indicate that green tea may help prevent cancer in humans.

The research shows that in some people, high doses of the green tea component epigallocatechin gallate (EGCG) increase the activity of a detoxification enzyme called glutathione S-transferase.

"This particular detoxification enzyme is responsible for getting rid of toxic chemicals - carcinogens," said Dr. Sherry Chow, research associate professor at the Cancer Center and principal investigator for the study.

Prior studies on animals have demonstrated green tea's detoxification properties, Chow said.

In the new study, 42 people were recruited and asked to refrain from consuming tea, she said.