Artificial Sweeteners May Be Screwing Up How Your Body Handles Sugar

By affecting gut microbes, artificial sweeteners may be messing with your metabolism

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For diabetics and the calorie conscious who steer clear of sugary foods, artificial sweeteners are a blessing. These undigestable synthetic compounds, like aspartame or saccharin, give foods a sweet taste but don't mess with a delicate blood glucose balance or add unwanted girth. Or, that's how they're supposed to work. Scientists are finding, though, that artificial sweeteners may mess with the body in curious ways—maybe even contributing to the problems they were meant to avoid.

In a new study, researchers found that both in mice and in people artificial sweeteners seem to contribute to glucose intolerance—a blanket term for metabolic problems that lead to high blood sugar, such as pre-diabetes or type 2 diabetes.

The link between sweeteners and metabolic problems, the scientists found, is none other than the microbiome—the reams of bacteria that live on and inside us. In this case, eating artificial sweeteners had an effect on which kinds of bacteria lived in the digestive tracts of mice, says Helen Thomson for New Scientist. Mice that ate a sweetener/glucose blend, rather than those that ate just glucose or just water, had a higher spike in blood sugar when later given a sugary treat.

The connection definitely has something to do with gut bacteria, too, says Thomson. Giving the mice antibiotics to wipe out their gut bacteria also eliminated their glucose intolerance. Transferring the bacteria from mice with sweetener-induced glucose problems to those without also transferred the metabolic issues.

Even in people, says the New York Times, the researchers were able to induce blood sugar problems using the Food and Drug Administration's recommended maximum dose of the sweeter saccharin, which is commercially available as Sweet'N Low. In a small trial of just seven people, four gained blood sugar problems reminiscent of the mice.

Scientists' understanding of the microbiome is still in its infancy, says Kai Kupferschmidt for Science magazine, and making any big decisions or sweeping changes based on this study would be premature. "We are the first to admit that the human arm in the study has only preliminary results on a small subset of individuals,” said one of the study's authors to Kupferschmidt.

Even if this line of research is still in its early stages, this isn't the first study to suggest a link between artificial sweeteners and metabolic problems. In a separate small study last year 17 obese people were given a different artificial sweetener, sucralose (which you can buy as Splenda) and also had elevated blood sugar levels, when compared to people who drank only water.

These findings give reason to pause. In their study, the authors suggest that the widespread use of artificial sweeteners at least deserves a second look.

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