Splenda-the calorie-free artificial sweetener-may leave consumers with something worse than a bitter aftertaste.

In a recent study, Duke University researchers found that Splenda may not be as healthy as previously thought, and may instead cause weight gain, kill beneficial intestinal bacteria and block the absorption of prescription drugs.

Over the course of 12 weeks, researchers gave varying dosages of Splenda to five groups of rats and then collected their fecal pellets. Though all of the rats consumed the same amount of food, the rats that received the Splenda treatment gained significantly more weight than the control group, and continued to do so even after treatment was stopped.

"We found that the [sucrose] actually causes a decrease in the microflora," said lead researcher Dr. Mohamed Abou-Donia, professor of pharmacology, cancer biology and neurobiology. "Generally, the microflora is responsible for the synthesis of vitamins and acts as protection from bad microbes."

But Dr. Pao-Hwa Lin, assistant research professor of medicine, noted that the results of the study cannot necessarily be applied to humans, although he acknowledged that Splenda could interfere with some medications.

"The company says that [Splenda] is derived from sugar, but there is some processing that is deriving this sucralose [and] we are not sure whether it is really safe or not," she said. "However, [the findings do] need to be confirmed in humans."

Because the study was performed on rats, some students said the results will not deter them from using the sugar substitute.

"The perception is that [artificial sweeteners] are healthier than pure sugar," freshman Zhe Ma said, adding that he prefers their taste to that of sugar.

Although the study was funded by the Sugar Association, which lobbies for the national sugar industry and sued Splenda in 2004, Abou-Donia said the group was not involved in conducting or analyzing the study.

"I had the idea of doing the study, and asked the Sugar Association if they would fund it. They said yes," he said. They did not, however, "have any input on the planning or performing [of] the study, interpretation of the results or [the] writing of the [study]," he said.

In previous studies, researchers discovered that between 60 and 95 percent of ingested sucralose-which is a component of Splenda-is not absorbed from the gastrointestinal tract. Abou-Donia wanted to find out what this excess sucralose does in the gut.

The findings of the study were posted on The Journal of Toxicology and Environmental Health's Web site, and will be published in the journal's print edition this month.