Artificial sweeteners create conditions for onset of diabetes, study suggests
Study suggests using sugar substitutes changes bacteria in our bodies in ways that make us more vulnerable to obesity and Type 2 diabetes
Diet soft drinks and the artificial sweetener you put in your coffee may not be as benign as we thought, a new study suggests.
High doses of saccharin, sucralose and aspartame can change the population of healthy gut bacteria in mice and in some humans. And those changes can affect how well their bodies metabolise sugar, according to a study published on Wednesday in the journal .
"We are by no means prepared to make recommendations about the use and dose of sweeteners, but these results should prompt additional study and debate on the massive use of artificial sweeteners," said Dr Eran Segal, a biologist at the Weizmann Institute of Science in Israel and an author of the paper.
Artificial sweeteners are not digested by the human body, which is why they have no calories. However, they must still pass through our gastrointestinal tract, where they encounter the vast ecosystem of bacteria that thrive in our guts. These bacteria, though not technically part of our bodies, still play an important role in our physiology, including how we process glucose and other sugars.
To find out whether artificial sweeteners affect healthy gut bacteria, the researchers added saccharine, sucralose or aspartame to the drinking water of different groups of mice. Other mouse groups got real sugars in their water, and a control group got plain, unsweetened water.
After 11 weeks, the mice that received the artificial sweeteners showed higher levels of glucose intolerance compared with the others - a sign that their bodies were doing a worse job of processing sugar. Among other things, this causes blood sugar to be too high, and is often a precursor to Type 2 diabetes.
To see whether the gut microbiome had anything to do with the link between drinking artificial sweeteners and developing glucose intolerance, the researchers gave the mice antibiotics for four weeks to pretty much wipe out their gut bacteria. After that time, all the mouse groups were able to metabolise sugar equally well.
This was the first evidence that the bacteria in the mice was being affected by the artificial sweeteners.
Next, the researchers transplanted gut bacteria from mice that had consumed saccharin into other mice that had no gut bacteria of their own. Six days later, those mice had lost some of their ability to process sugar.
Genetic analysis revealed that the composition of the gut bacteria in mice had indeed changed after exposure to the artificial sweetener - some types of bacteria became more abundant, while others shrank.
"Many of the pathways that changed are pathways that have been previously linked to susceptibility of obesity and adult onset diabetes," said Dr Eran Elinav, another study author at the Weizmann Institute.
The most obvious question, of course, is whether artificial sweeteners would have the same effect on the guts of humans as they do on the guts of mice.
The researchers made some preliminary attempts to answer this question.
First, they looked at a group of 381 people who are involved in a continuing clinical nutritional study and found that the gut bacteria of people who regularly consumed artificial sweeteners looked different from people who did not. But they could not say that either artificial sweeteners or gut bacteria were causing weight gain or high blood-sugar levels.
Finally, the researchers ran an experiment with seven healthy, non-obese volunteers who did not regularly consume artificial sweeteners. For one week, these seven people were given high doses of artificial sweeteners. Four of the people in the study developed an impaired glycaemic response by the end of the week, meaning they lost some of their ability to metabolise sugar. Meanwhile, the other three people saw no change at all.
"The data in mice are very, very clear," said Dr Cathryn Nagler, who studies the microbiome at the University of Chicago. "The limited amount of research they did on humans at least suggests we need to examine our artificial sweetener use more carefully."
