Consumption of noncaloric artificial sweeteners (NAS) such as saccharin, sucralose and aspartame has been tentatively linked to metabolic syndrome. Eran Elinav and his colleagues (Nature 10.1038/nature13793) now find a connection between NAS consumption, glucose intolerance and changes in the gut microbiota in mice and humans.

NAS consumption over several weeks induced glucose intolerance in both lean and obese mice. Antibiotic treatment prevented this, suggesting a role for the host microbiota. Fecal transplantation from a NAS-fed mouse to a germ-free host also induced glucose intolerance, in the absence of host NAS consumption. The effect of NAS on gut microbial content was direct, as transplant of fecal samples from naive mice that had been cultured with saccharin to germ-free mice led to host microbiota changes that were similar to those caused by dietary consumption.

The authors also found that in humans, self-reported levels of long-term NAS consumption are correlated with clinical measures of metabolic syndrome. A causative role for NAS in abnormal metabolic parameters was also established in a small short-term trial, in which NAS-naive individuals consumed saccharin for 1 week. This led to deterioration in glycemic responses in four out of the seven people studied that was mirrored by changes in the gut microbiota. These findings suggest dietary NAS consumption has a negative effect on metabolism in some individuals.