Year in review: Gut reacts to artificial sweeteners

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It wasn’t a bittersweet year for saccharin — just bitter. An elaborate study demonstrated that the artificial sweetener messes with the body’s ability to metabolize glucose, a condition that often presages diabetes, obesity and other metabolic problems (SN: 10/18/14, p. 6). The kicker: Microbes in the gut seem to mediate this off-kilter metabolism, although scientists don’t know how.

Israel-based researchers first established that blood sugar levels in mice got wonky after the mice consumed artificial sweeteners, then used antibiotic treatments to probe the saccharin-gut microbe connection. The team gathered genetic data on those microbes and even transplanted the fecal microbial community of mice — and of two humans — into other mice.

The study got a lot of attention, probably buoyed by a growing interest in gut microbes’ influential reach, says endocrinologist Kristina Rother of the National Institutes of Health in Bethesda, Md. “People are much more aware that what we eat and what our intestinal flora looks like contribute to health — the microbiome is so hot right now.”

The new study was not the first to find that artificial sweeteners don’t pass through the gut unnoticed, she says. For years, scientists have been dissolving the sweeteners’ sugar-coating, revealing that the sweet substitutes interact much more with the body than anticipated and often with metabolic consequences. Just stimulating gut cells that respond to sweet taste can have downstream metabolic effects, researchers reported in 2007. The link with altered gut microbes was made in rats back in 2008.

Yet in a world where calories are criminal, artificial sweeteners have been presented as good guys or at worst innocent bystanders. “There is now more and more evidence that artificial sweeteners are not metabolically inert,” Rother says. “But I still hear people, even at the NIH, say, ‘What do you mean they affect metabolism? They have no calories!’ ”

While the scientific evidence mounts that artificial sweeteners alter metabolism in potentially problematic ways, consumers have little recourse. Google can help searchers find the acceptable daily amount of the sweeteners, but nutrition labels don’t give a percentage of daily dose. In fact, people who prefer not to eat artificial sweeteners often inadvertently choose products laden with them because those foods are often labeled as “low sugar” or “no sugar added,” says Rother. “The FDA and industry are a step behind what the consumer would like. But the pressure is rising.”