A diabetic has his blood sugar level measured in downtown..
(photo credit: REUTERS)
Calorie-free artificial sweeteners, which most people believe will help them lose weight and prevent the onset of diabetes, could actually speed up the development of glucose intolerance and metabolic disease, according to a recent Israeli study.
The study, which was published in the journal Nature, was conducted by Dr. Eran Elinav of the immunology department at Rehovot’s Weizmann Institute of Science, and Prof. Eran Segal from the institute’s computer science and applied mathematics department.
The Weizmann scientists, who experimented on mice and humans, suggested that widespread use of artificial sweeteners in diet drinks and food may be contributing to the obesity and diabetes epidemic that is sweeping much of the world.
Elinav said that the chemicals may bring on diabetes by changing the composition and function of the microscopic natural flora in the gut.
Researchers have been puzzled over the fact that non-caloric artificial sweeteners do not seem to help reduce weight, and some studies have suggested they may even have an opposite effect.
Graduate student Jotham Suez from Elinav’s lab led the study with colleagues from Elinav’s and Segal’s labs. They discovered that saccharine and other artificial sweeteners, even though they do not contain sugar, nonetheless have a direct effect on the body’s ability to utilize glucose.
Glucose intolerance – generally thought to occur when the body cannot cope with large amounts of sugar in the diet – is the first step on the path to metabolic syndrome and adult-onset diabetes.
The researchers did not study Stevia, a low-calorie sweetener made from concentrates of leaves from the natural green plant of that name.
The scientists gave mice in the lab water laced with saccharine and two other similar and commonly used sweeteners in the equivalent amounts to those permitted by the US Food and Drug Administration. These mice developed glucose intolerance, compared to mice that drank water or sugar water.
Repeating the experiment with different types of mice and different doses of the sweeteners produced the same results – these substances were somehow inducing glucose intolerance.
Next, the researchers investigated a hypothesis that the gut flora are involved in this phenomenon and suggested the bacteria might do this by reacting to new substances like artificial sweeteners, which the body itself may not recognize as “food.”
They found that artificial sweeteners are indeed not absorbed in the gastrointestinal tract, but in passing through they encounter trillions of the bacteria in the gut.
The researchers treated mice with antibiotics to kill off most of their gut bacteria; this resulted in a full reversal of the artificial sweeteners’ effects on glucose metabolism. Next, they transferred the bacteria from mice that consumed the three kinds of artificial sweeteners to ‘germ-free’ mice – resulting in a complete transmission of the glucose intolerance into the recipient mice.
The team noted profound changes to their bacterial populations, including new microbial functions that are known to lead to obesity, diabetes and complications of these problems in both mice and humans.
They then 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 glucose levels and gut flora tests.
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 flora explained the difference: The researchers discovered two different populations of human gut bacteria – one that induced glucose intolerance when exposed to the sweeteners, the second that had no effect either way.
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