Pink, yellow, or blue? Each of these non-caloric sweeteners may be contributing to the global epidemic of diabetes. The study published in Nature today (Sept. 17, 2014), shows the non-nutritive sweeteners, saccharin, sucralose and aspartame, could actually hasten the development of glucose intolerance and metabolic disease. The mechanism is surprising: these no-calorie sweeteners change the composition and function of gut microbiota. The researchers found the results so compelling they went so far as to call for a reassessment of non-nutritive sweeteners.
“Our relationship with our own individual mix of gut bacteria is a huge factor in determining how the food we eat affects us. 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,” said Dr. Eran Elinav of the Weizmann Institute’s Immunology Department, who led this research together with Prof. Eran Segal of Computer Science and Applied Mathematics Department.
These findings, the results of experiments in mice and humans, are the evidence that many have suspected but found little proof until now. “Widespread use of artificial sweeteners in drinks and food may be contributing to the obesity and diabetes epidemic that is sweeping much of the world,” says Elinav. He believes that certain bacteria in the guts of those who developed glucose intolerance reacted to the chemical sweeteners by secreting substances that then provoked an inflammatory response similar to sugar overdose, promoting changes in the body’s ability to utilize sugar.
Sugar Substitutes More Damaging than Sugar Water
The scientists gave mice water laced with the three most commonly used artificial sweeteners – in the equivalent amounts to those permitted by the FDA. These mice developed glucose intolerance, as compared to mice that drank water, or even sugar water. Repeating the experiment with different types of mice and different doses of the sweeteners produced the same results – these substances were somehow inducing glucose intolerance.
Next, the researchers investigated a hypothesis that the gut microbiota are involved in this phenomenon. They thought the bacteria might do this by reacting to new substances like artificial sweeteners, which the body itself may not recognize as “food.” Indeed, artificial sweeteners are not absorbed in the gastrointestinal tract, but in passing through they encounter trillions of the bacteria in the gut microbiota.
The researchers treated mice with antibiotics to eradicate many of their gut bacteria; this resulted in a full reversal of the artificial sweeteners’ effects on glucose metabolism. Next, they transferred the microbiota from mice that consumed artificial sweeteners to ‘germ-free’ mice – resulting in a complete transmission of the glucose intolerance into the recipient mice. This, in itself, was conclusive proof that changes to the gut bacteria are directly responsible for the harmful effects to their host’s metabolism. The group even found that incubating the microbiota outside the body, together with artificial sweeteners, was sufficient to induce glucose intolerance in the sterile mice. A detailed characterization of the microbiota in these mice revealed profound changes to their 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.
Human Experiments Show Similar Results
Dr. Eran Elinav’s research is supported by the Abisch Frenkel Foundation for the Promotion of Life Sciences; the Benoziyo Endowment Fund for the Advancement of Science; the Gurwin Family Fund for Scientific Research; the Leona M. and Harry B. Helmsley Charitable Trust; the Adelis Foundation; Yael and Rami Ungar, Israel; the Crown Endowment Fund for Immunological Research; John L. and Vera Schwartz, Pacific Palisades, CA; the Rising Tide Foundation; Alan Markovitz, Canada; Cynthia Adelson, Canada; the estate of Jack Gitlitz; the estate of Lydia Hershkovich; the European Research Council; the CNRS – Centre National de la Recherche Scientifique; the estate of Samuel and Alwyn J. Weber; and Mr. and Mrs. Donald L. Schwarz, Sherman Oaks, CA. Dr. Elinav is the Incumbent of the Rina Gudinski Career Development Chair
Prof. Eran Segal’s research is supported by the Kahn Family Research Center for Systems Biology of the Human Cell; the Carolito Stiftung; the Cecil and Hilda Lewis Charitable Trust; the European Research Council; and Mr. and Mrs. Donald L. Schwarz, Sherman Oaks, CA.