Coke Zero, how could you? (artificial sweeteners and glucose intolerance)

mouse and aspartame


In theory, artificial sweeteners were created to help consumers avoid traditional sugar in an attempt to avoid caloric intake and curb the metabolic consequences, such as obesity and diabetes. However, a recently published study in Nature suggests otherwise.

Sugar substitutes such as saccharin might aggravate these metabolic disorders by acting on bacteria in the human gut, according to a study published by Nature this week (J. Suez et al. Nature; 2014). Smaller studies have previously purported to show an association between the use of artificial sweeteners and the occurrence of metabolic disorders. This is the first work to suggest that sweeteners might be exacerbating metabolic disease, and that this might happen through the gut microbiome, the diverse community of bacteria in the human intestines. “It’s counter-intuitive — no one expected it because it never occurred to them to look,” says Martin Blaser, a microbiologist at New York University.

A team led by Eran Elinav of the Weizmann Institute of Science in Rehovot, Israel, fed mice various sweeteners — saccharin, sucralose and aspartame — and found that after 11 weeks, the animals displayed glucose intolerance, a marker of propensity for metabolic disorders.

To simulate the real-world situation of people with varying risks of these diseases, the team fed some mice a normal diet, and some a high-fat diet, and spiked their water either with glucose alone, or with glucose and one of the sweeteners, saccharin. The mice fed saccharin developed a marked glucose intolerance compared to those fed only glucose. But when the animals were given antibiotics to kill their gut bacteria, glucose intolerance was prevented. And when the researchers transplanted faeces from the glucose-intolerant saccharin-fed mice into the guts of mice bred to have sterile intestines, those mice also became glucose intolerant, indicating that saccharin was causing the microbiome to become unhealthy.

So his team recruited seven lean and healthy volunteers, who did not normally use artificial sweeteners, for a small prospective study. The recruits consumed the maximum acceptable daily dose of artificial sweeteners for a week. Four became glucose intolerant, and their gut microbiomes shifted towards a balance already known to be associated with susceptibility to metabolic diseases, but the other three seemed to be resistant to saccharin’s effects. “This underlines the importance of personalized nutrition — not everyone is the same,” says Elinav.

He does not yet propose a mechanism for the effect of artificial sweeteners on the micro­biome. But, says Blaser, understanding how these compounds work on some species in the gut might “inspire us in developing new therapeutic approaches to metabolic disease”.

Portions of this post are reprinted by permission from Macmillan Publishers Ltd: Nature, advance online publication, volume: 513, pages: 290. 18 September 2014(doi: 10.1038/513290a)