Artificial Sweeteners May Cause Gut Bacteria to Change: Glucose Intolerance Isn't So Sweet

Artificial sweeteners have long puzzled scientists. While they're supposedly non-caloric, they don't seem to assist in weight loss. Now, researchers may have an explanation; they've found that artificial sweeteners may hasten the development of glucose intolerance and metabolic disease by changing the composition and function of gut bacteria.

For years, researches have wondered why non-caloric artificial sweeteners don't help with weight loss. In fact, some studies have suggested that they do the opposite and cause weight gain. Determined to get to the bottom of the issue, researchers used mice to study the role of artificial sweeteners a bit more closely.

The scientists gave mice water laced with the tree most commonly used artificially sweeteners in amounts that were equivalent to those permitted by the U.S. Food and Drug Administration (FDA). Surprisingly, they found that these mice developed glucose intolerance in comparison to mice that drink only water or even sugar water. They found the same result, even with different types of mice and different doses of the artificial sweeteners.

Intrigued by this fact, the scientists decided to see whether gut bacteria might be involved. The researchers first treated mice with antibiotics to eradicate many of their gut bacteria. This actually caused a full reversal of the artificial sweeteners' effects on glucose metabolism. Then, they transferred the microbiota from mice that consumed artificial sweeteners to sterile mice; this resulted in a full transmission of the glucose intolerance.

What was more disturbing was when the researchers analyzed the microbiota in the affected mice a bit more closely. They found profound changes to the bacterial populations, including new microbial functions that are known to infer a propensity to obesity, diabetes and complications of these problems in both mice and humans.

But did this happen in humans, as well? The scientists turned to data collected from their Personalized Nutrition Project, the largest human trial to date to examine the connection between nutrition and microbiota. In the end, they found there was a significant association between self-reported consumption of artificial sweeteners, personal configurations of gut bacteria and the propensity for glucose intolerance.

"Our relationship with our own individual mix of gut bacteria is a huge factor in determining how the food we eat affects us," said Eran Elinav, one of the researchers, in a news release. "Especially intriguing is the link between use of artificial sweeteners-through the bacteria in our guts-to a tendency to develop the very disorders they were designed to prevent; this calls for reassessment of today's massive, unsupervised consumption of these substances."

The findings are published in the journal Nature.