A recent Nature study has reportedly concluded that non-caloric artificial sweeteners (NAS) elevate blood glucose levels and induce glucose intolerance by modifying gut bacteria. Jotham Suez, et al., “Artificial sweeteners induce glucose intolerance by altering the gut microbiota,” Nature, September 2014. Noting that mice given drinking water prepared with either saccharin, sucralose or aspartame showed signs of metabolic problems not evident in mice that received only sucrose water, Israeli researchers evidently hypothesized that gut bacteria mediates the effect of NAS on glucose response. To test this theory, they first showed that eradicating the gut microbiota in these mice also leveled the metabolic differences between the two groups. In addition, germ-free mice that received fecal transplants from those on the NAS diet likewise developed a reduced tolerance to glucose.

The study’s authors then obtained gut-bacteria samples from seven human volunteers who consumed the maximum recommended amount of saccharin for one week. When given to germ-free mice, the fecal transplants from the four participants who showed a reduced insulin response transferred this effect to the recipients. The researchers reported that not only did NAS appear to change the types and number of bacteria present in the gut, but that the remaining population expressed DNA differently.

At the same time, however, three of the human test subjects did not develop any signs of glucose intolerance. “This underlines the importance of personalized nutrition—not everyone is the same,” said the lead author of the study, which calls for “a reassessment of massive NAS usage.” See Ars Technica, September 17, 2014; Nature News, September 18, 2014.