A controversial animal study, with a very small follow-up in humans, suggests that artificial sweeteners may promote glucose intolerance-and therefore diabetes-by changing the bacterial mix in the gut. Published in the journal Nature, the findings have some saying artificial sweeteners should be viewed with suspicion, while other experts dismiss the results.
This is a hard study to evaluate, says Susan B. Roberts, PhD, Tufts professor of nutrition and founder of the online iDiet weight loss program <www.myidiet.com>. On the one hand, the results are fairly clear: Mice fed artificial sweeteners at a level equivalent to the maximum daily recommended amount for humans had impaired glucose tolerance, and that seemed to be due to metabolic effects resulting from a different balance of bacteria living in the large intestine. I realize that sounds unlikely, but in fact intestinal bacteria have increasingly been shown to have quite powerful effects throughout the body.
In the study, researchers at the Weizmann Institute of Science in Israel fed mice water containing sugar or one of three noncaloric sweeteners. They published results focused on saccharin, which had the greatest effects. After 12 weeks, mice given saccharin showed an unusually high spike in blood sugar (glucose) levels after being given a high-glucose meal-a sign of glucose intolerance.
Certain types of gut microbes were more common in the saccharin-fed mice. When intestinal bacteria from these mice were transplanted to healthy mice, those animals also developed glucose intolerance.
WHAT ABOUT HUMANS?: Says Roberts, The harder question is what this means for us. The researchers did also give high doses of saccharin-five milligrams per kilogram of body weight, the FDAs maximum acceptable daily intake-to seven human volunteers for six days. Four began to show signs of glucose intolerance, while the others (labeled non-responders) did not.
Clearly, not all artificial sweeteners will have the same effects, says Roberts, since the effect of one non-digestible chemical on the intestinal florae will not be the same as the effect of a different chemical-and for the most part the sweeteners on the market all have really different chemical compositions. However, the specter has been raised that artificial sweeteners need more scrutiny, and clearly more research is needed on all the sweeteners existing in the marketplace today.
Her iDiet program allows participants optional use of artificial sweeteners as an aid to transitioning into a lower-sugar diet. But Roberts says, Based on this new research, I think it may be good to stay away from saccharin while we wait for new research to confirm or reject the new study results. I dont think the evidence is there yet to avoid other sweeteners.
For more on artificial sweeteners, see our September 2014 Special Report.