Stevia, which is about 100 times sweeter than sugar, is obtained from a shrub (yerba dulce) that is grown in Brazil, Paraguay, southeast Asia, and elsewhere. The actual sweet chemicals are the closely related stevioside and rebaudioside A. Stevia and its derivatives are said to be the holy grail of high-potency sweeteners, because they are naturally derived alternatives to the often-controversial synthetic sweeteners (saccharin, aspartame, acesulfame-K, sucralose, cyclamate). Stevia has been used in Japan and several other countries. Still, many people perceive stevia and its sweet derivatives to have a foul taste in certain foods.

Just because a substance is natural, does not mean that it is safe. In the 1990s, the U.S. FDA rejected stevia for use as a food ingredient. Likewise, Canada did not approve stevia, and a European Community scientific panel declared that stevia was unacceptable for use in food. High dosages fed to rats reduced sperm production and increased cell proliferation in their testicles, which could cause infertility or other problems. Pregnant hamsters that had been fed large amounts of a derivative of stevioside called steviol had fewer and smaller offspring. In the laboratory, steviol can be converted into a mutagenic compound, which may promote cancer by causing mutations in the cells' DNA.

In the 21st century, Cargill and Merisant (which marks aspartame-based Equal) developed extracts of stevia that are 95 percent pure rebaudioside A and 200 times as sweet as sugar. The companies call their products Truvia and PureVia, respectively, with the nickname of rebiana. In 2008, Cargill and Merisant told the FDA that rebiana should be considered "generally recognized as safe," or GRAS. (GRAS substances are given less scrutiny by the FDA than standard food additives.) A third company, Wisdom Natural Brands, declared that its stevia-related product to be GRAS without even notifying the FDA.

UCLA toxicologists and the Center for Science in the Public Interest, however, urged the FDA to reject the GRAS claims for rebiana. They reported that FDA's guidelines call for major new food additives to be tested for two years on both rats and mice, but rebiana had only been tested on rats. The toxicologists and CSPI said that testing of rebiana in both rats and mice is particularly important, because several tests found that rebiana-related substances caused mutations and damaged chromosomes or DNA.

Despite the disagreement about rebiana's safety, just before Christmas 2008 the FDA agreed that the chemical could be considered GRAS. Shortly thereafter, beverage companies started marketing rebiana-sweetened products. If consumers find the taste acceptable and future tests do not find major risks, rebiana may well be the elusive natural non-caloric sweetener that industry has sought for decades.


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