Seems sort of counterintuitive, doesn’t it? The sweeteners that have been developed to help people control their weight and avoid diabetes that are featured in diet soda, yogurt and other foods can raise the blood sugar level instead of reducing it, according to new experiments in mice and people.
The provocative finding—made possible through a new avenue of research—is likely to stoke the simmering controversy over whether artificial sweeteners help or hinder people’s ability to lose weight and lower their risk of diabetes.
The research shows that zero-calorie sweeteners such as saccharin, sucralose and aspartame can alter the population of bacteria in the gut and trigger unwanted changes such as higher blood glucose levels—a risk factor for diabetes.
“The scope of our discovery is cause for a public reassessment of the massive and unsupervised use of artificial sweeteners,” said Eran Elinav, a physician and immunologist at Israel’s Weizmann Institute of Science and lead author of the study, which appeared Wednesday in the journal Nature.
Though many people consume artificial sweeteners instead of sugar to control their weight, the scientific evidence that they work is mixed. Some studies have indicated that the sweeteners can help lead to weight loss, while others suggest they contribute to weight gain.
One reason is that it isn’t clear whether people who consume artificial sweeteners are overweight because of what they eat—or whether overweight people are the ones who typically gravitate to such products.
Based on existing evidence, guidelines jointly published in 2012 by the American Heart Association and the American Diabetes Association noted that artificial sweeteners “when used judiciously…could facilitate reductions in added sugar,” and thus influence weight loss.
The new Nature study marks a significant advance because it brings together two separate areas of research—the role of sweeteners in raising blood sugar levels, and the complex workings of the vast colonies of bacteria that inhabit the gut. Individuals can have differing bacterial colonies in their gut, meaning people respond differently to what they consume.
In one experiment, the researchers found that mice whose diets included saccharin, sucralose or aspartame had significantly higher blood-glucose levels than mice whose diet included sugar, or no sugar at all.
They next wanted to test whether the fake sweeteners caused that metabolic change by altering the balance of microbes in the animals’ gut.
They transplanted bacteria from artificial-sweetener-fed mice or sugar-fed mice into other mice that were bred to have no gut bacteria of their own and that had never consumed a sweetener product. They found that the bacterial transfer from the sweetener-fed mice raised the blood sugar levels in the transplant recipients—suggesting that the gut microbes had triggered the higher sugar levels in mice fed fake sweeteners.
Was the same link true for people? Dr. Elinav and his colleagues examined the relationship between long-term consumption of artificial sweeteners and various metabolic measurements in some 380 nondiabetic people.
They found that the bacteria in the gut of those who regularly ate fake sweeteners were notably different from those who didn’t. In addition, there was a correlation between the sweetener consumption and a susceptibility to glucose intolerance, which is a disturbance in the blood glucose level.
Correlation, however, doesn’t necessarily mean causation. In the next experiment, seven volunteers who normally didn’t consume fake sugar were asked to consume products high in the sweeteners. After four days, four of them had significantly higher blood-sugar levels as well as altered populations of bacteria in their gut—an outcome similar to what was seen in mice.
“This susceptibility to sweeteners [can now] be predicted ahead of time by profiling the microbes in the people,” said Eran Segal, a co-author of the study and computational biologist at the Weizmann Institute.
The results need to be corroborated through a study with many more participants.
In a statement, the Calorie Control Council, a trade group that represents makers of artificial sweeteners and other food products, said the Nature study suffered from several limitations. It said the results from the mouse experiments may not apply to humans, while the human experiments had a small sample size. It said further research was needed.
FoodFacts.com has never had anything good to say about artificial sweeteners. Reports of negative health effects have far outweighed the marketed benefits. Research like this points straight to the idea that artificial sweeteners are not only unnecessary, but actually harmful — harmful enough that Dr. Elinav, the study’s lead author, stopped using them completely once he saw the results. That should certainly tell us something.