(NaturalNews) The FDA has sent a warning letter to the Hain Celestial Group, instructing the natural and organic food producer to relabel certain products that contain the sweetener stevia. The letter concerned the Celestial Zingers To Go tea and drink mix products, which the FDA charges are being labeled and marketed as food products, even though an ingredient they contain -- the stevia herb -- has not been approved for use in foods in the United States.Stevia, derived from a South American plant, has become popular as a sweetener because it has 300 times the sweetness of table sugar but almost no impact on blood glucose levels. Its taste is said to have a slower onset than that of sugar and to last longer.Stevia has been approved for use in food and beverage products in a number of countries, including Brazil, Canada, China and Japan, but to date the FDA has only approved it as an ingredient in dietary supplements.In response to the warning letter, Hain Celestial Group removed the term "iced tea mix" from all labels of the products in question, and made the words "herbal supplement" much more prominent.In light of the increasing popularity of stevia and the fact that companies like Hain Celestial have apparently been trying to get around regulations of its use, the FDA said that it expects to soon receive a petition to approve the sweetener for use in foods. Reportedly, both the Coca-Cola Company and Cargill are interested in producing stevia-sweetened products, with Coca-Cola having filed 24 patent applications related to the sweetener.But the FDA said that current information is not sufficient to prove stevia safe as an ingredient for food."Data and information necessary to support the safe use have been lacking," the FDA's letter to Hain Celestial read. "In fact, literature reports have raised safety concerns about the use of stevia, including concerns about control of blood sugar and the effects of reproductive, cardiovascular and renal systems."Consumer health advocate Mike Adams, a long-time supporter of stevia, disagrees. "The FDA has been stalling on stevia approval for well over a decade in order to protect the profits of aspartame," Adams said. "Stevia is safely used around the world by hundreds of millions of consumers with absolutely no problems, while aspartame is tied to seizures, blindness, headaches and other serious neurological problems. The FDA once ordered the destruction of books containing stevia recipes. That's how desperate this criminal organization is to protect the profit racket of aspartame," Adams concluded.