Artificial sweeteners -- promoted as aids to weight loss and diabetes prevention -- could actually hasten the development of glucose intolerance and metabolic disease, by changing the composition and function of the gut microbiota -- the substantial population of bacteria residing in our intestines.
The findings from experiments in mice and humans were published September 17 in Nature. The researchers say that the widespread use of artificial sweeteners in drinks and food may be contributing to the obesity and diabetes epidemic that is sweeping much of the world.
For years, researchers have been puzzling over the fact that non-caloric artificial sweeteners do not seem to assist in weight loss, with some studies suggesting that they may even have an opposite effect. Yet researchers have discovered that artificial sweeteners, even though they do not contain sugar, have a direct effect on the body's ability to utilize glucose. Glucose intolerance -- thought to occur when the body cannot properly process large amounts of sugar in the diet -- is the first step to metabolic syndrome and adult-onset diabetes.
The scientists gave mice water laced with the three most commonly used artificial sweeteners, in amounts equivalent to those permitted by the U.S. Food and Drug Administration (FDA). These mice developed glucose intolerance, as compared to mice that drank water, or even sugar water. Repeating the experiment with different types of mice and different doses of the artificial sweeteners produced the same results -- these substances were somehow inducing glucose intolerance.
Next, the researchers investigated a hypothesis that the gut microbiota are involved by reacting to new substances like artificial sweeteners, which the body itself may not recognize as "food." Artificial sweeteners are not absorbed in the gastrointestinal tract. As they pass through they encounter trillions of the bacteria in the gut microbiota.
The researchers treated mice with antibiotics to eradicate many of their gut bacteria; this resulted in a full reversal of the artificial sweeteners' effects on glucose metabolism. Next, they transferred the microbiota from mice that consumed artificial sweeteners to "germ-free," or sterile, mice -- resulting in a complete transmission of the glucose intolerance into the recipient mice. This proved that changes to the gut bacteria are directly responsible for the harmful effects to their host's metabolism. The researchers even found that incubating the microbiota outside the body, together with artificial sweeteners, was sufficient to induce glucose intolerance in the sterile mice.
To find out if the human microbiome reacts the same way, the researchers looked at data collected from their Personalized Nutrition Project, the largest human trial to date to look at the connection between nutrition and microbiota. Here, they uncovered a significant association between self-reported consumption of artificial sweeteners, personal configurations of gut bacteria, and the propensity for glucose intolerance. They next conducted a controlled experiment, asking a group of volunteers who did not generally eat or drink artificially sweetened foods to consume them for a week, and then undergo tests of their glucose levels and gut microbiota compositions.
The findings showed that many -- but not all -- of the volunteers had begun to develop glucose intolerance after just one week of artificial sweetener consumption. The composition of their gut microbiota explained the difference: the researchers discovered two different populations of human gut bacteria -- one that induced glucose intolerance when exposed to the sweeteners and one that had no effect either way.
The researchers believe that certain bacteria in the guts of those who developed glucose intolerance reacted to the artificial sweeteners by secreting substances that then provoked an inflammatory response similar to sugar overdose, promoting changes in the body's ability to utilize sugar.
According to the scientists, our relationship with our own individual mix of gut bacteria is a huge factor in determining how the foods we eat affects us. They also state that these new findings call for reassessment of today's massive consumption of artificial sweeteners.
Source: Nature, 2014.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.