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Could Diet Sodas Be Making Us Fatter?

By Carl Engelking
Sep 18, 2014 11:36 PMNov 20, 2019 4:06 AM


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The artificial sweeteners in “diet” beverages, thought to help people trim their waistlines, may be having the opposite effect. A new study reveals that three of the leading artificial sweeteners produce an increase ­in blood-sugar levels in both mice and humans, by disrupting the balance of helpful gut bacteria. High blood-sugar levels, in turn, are the telltale sign of glucose intolerance, a condition which can evolve into diabetes and metabolic disease.

It Takes Guts

The role artificial sweeteners play in the obesity epidemic is far from settled: some studies say artificial sweeteners are beneficial for weight-watchers; other studies show these sweeteners can lead to weight gain. The current study falls into the latter category. To start, researchers added saccharin, aspartame or sucralose (common artificial sweeteners) to the drinking water of three groups of mice for 11 weeks. These mice were compared with two other groups: one that drank plain water, and another with authentic sugar water. Surprisingly, after five weeks, the blood-sugar levels of mice that consumed the artificial sweeteners were significantly higher than mice from the plain water and sugar water groups. To test if this was due to the mice's gut microbiome, researchers then transplanted the gut bacteria of mice fed artificial sweeteners into mice bred to have no gut bacteria. The mice on the receiving end of the transplant soon developed glucose intolerance as well. Based on this evidence, it was clear that artificial sweeteners were having a detrimental effect on the gut’s bacterial balance.

From Mice to Men

The evidence in mice was compelling enough for researchers to test their hypothesis in humans. Researchers compared the gut bacteria of 172 individuals and found that the microbial communities in the guts of people who regularly consumed artificial sweeteners were significantly different from people who did not. And, compellingly, sweetener-consumers had populations of microbes associated with glucose intolerance similar to those seen in the mice. As a final test, researchers asked seven people who didn’t consume artificial sweeteners to introduce them to their diet. For a week, participants ate the maximum federally approved intake of saccharin each day. Within the test period, four of the seven participants developed some glucose intolerance. Researchers published their findings Wednesday in the journal Nature. 

Is My Diet Doomed?

To be clear, researchers aren’t certain how artificial sweeteners and gut microbes interact to produce glucose intolerance. Furthermore, not everyone in the small human trial experienced the same reaction. Many things influence our metabolism, and some people may be more sensitive than others to artificial sweeteners, as Forbes reports. In the world of dieting, sometimes if feels like you’re damned if you do, and damned if you don’t.

Photo credit: ValeStock / Shutterstock.com

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