Others, however, are much more critical. “On this evidence, I'd agree that lab mice shouldn't have lots of sweeteners in their drinking water,” writes Catherine Collins, a dietitian at St. George’s Hospital in London, in a statement distributed by the
Science Media Centre. Lab mice get a much lower part of their calories from carbohydrates than humans do, she points out. “Our naturally higher carbohydrate intake has generated bowel bacteria happily digesting whatever we swallow, and their symbiotic relationship with our bowel cells and beyond is testimony to this.”
The data on humans, from just seven people, of which four show an effect, are far from convincing, O’Rahilly says. "If this had been sent to a clinical research journal there would have been a lot of questions.” Previous research also seems to point in a different direction. A large epidemiological study involving tens of thousands of people published last year found a connection between sugar-sweetened beverages and diabetes,
but not between artificially sweetened soft drinks and diabetes.[...]
One possible explanation for the discrepancy with large-scale epidemiological studies is that the new study centers on saccharin, a sweetener not used in any of the major soft drinks. In early studies, the researchers also tested aspartame—by far the most widely used soft drink sweetener—but the observed effect was smaller, and they dropped it. "The authors are confounding their conclusions by addressing all these noncaloric artificial sweeteners together,” says Brian Ratcliffe, a nutrition researcher at Robert Gordon University in Aberdeen, U.K. That's why the title of the paper, “Artificial sweeteners induce glucose intolerance by altering the gut microbiota,” is misleading, he says. "I cannot believe the journal allowed that title.” Still, he says, the data "certainly does suggest that there is something more that needs to be explored about saccharin."