We are more bacteria than we are human: for every cell in our body, we host no fewer than ten microbes, most of them in our gut (our gut microbiota or gut flora). Just recently, scientists have only begun to get a better understanding of the role that these hundreds of trillion of bacteria play inside us, mainly in our digestive tract. Now scientists know, for instance, that these bacteria are important to be in good health and that we can influence this fragile ecosystem with our diet and daily habits.
Proof of this is with a new, controversial study suggesting that artificially sweetened food may have a negative impact on the gut microbiota, leading to higher blood sugar levels, a condition that can be a precursor to diabetes. The animal study, published in Nature by researchers at the Weizmann Institute for Science in Revohot, Israel, concludes that artificial sweeteners such as saccharine or aspartame (frequently used in coffee, beverages and prepared food as a substitute for sugar) could, paradoxically, exacerbate the exact problems they are meant to solve: diabetes and obesity.
In the study, led by Dr Eran Elinav and Dr Eran Segal, one group of mice were fed with water containing sugar, while another received water with one of the three most popular non-caloric sweeteners: aspartame, saccharin or sucralose. Eleven weeks later, they found that rodents who were fed on artificial sweeteners had a tendency to develop a condition called ‘glucose intolerance’, which is considered to be a preliminary stage in the development of diabetes.
The animals showed an unusually high spike in their blood glucose levels when they were given the glucose meal. Researchers also observed that if they gave mice antibiotics during those four weeks, this high glucose spike did not happen, what may suggest, according to researchers, that gut microbiota may play a role.
The Israeli researchers also found that some types of gut bacteria were more common in mice that were fed with artificial sweeteners than in the mice fed with sugar. Although the precise mechanism is unknown, scientists believe that molecules produced by some bacteria may seem to increase glucose production in the body and trigger blood glucose levels.
To see whether these preliminary findings could be extended to human beings, they also ran tests on almost 400 individuals and discovered that people who consumed more artificial sweeteners were heavier, had more changes in their gut microbiota composition and tended to have a higher prevalence of glucose intolerance. Moreover, they monitored seven people to whom they administered during 6 days the maximum daily dose of saccharin recommended by the American Food and Drug Administration: 5 milligrams per kilogram of body weight. (To give a precise idea of how much that is: each of those doses was enough to sweeten around 40 cans of diet soft drinks.)
At the end of the experiment, four out of seven volunteers also began showing signs of glucose intolerance and, what’s more, their gut microbiota seemed to mirror the changes seen previously in mice. Researchers admitted they were completely unaware that the mechanisms in artificial sweeteners might cause a population increase in some gut bacteria and population collapse in others.
The authors of the study reported in Nature that “artificial sweeteners may have directly contributed to enhancing the exact diabetes epidemic that they themselves were intended to fight”. Nevertheless, many scientists are very skeptical of these results. Several expert voices have come out, warning that findings that are based on a sample size of only seven subjects are far from convincing, and reminding readers that sizeable studies in people have already shown that sugar substitutes can help test subjects to maintain a healthy weight and to ward off diabetes. Another fact that’s being excoriated is that the quantity of artificial sweeteners used in the study was totally unrealistic: “Nobody consumes so much”, experts agree. Moreover, they add, findings from mice cannot be directly translated to humans, due to differences between species. Last, but not least, only three types of artificial sweeteners have been analysed. Conclusions, therefore, can’t be generalized to the whole category.