A new study published Sept. 17 in the journal Nature says that artificial sweeteners found in diet soda, yogurt and other foods consumed by millions of people may actually raise blood sugar levels instead of lowering them, the Wall Street Journal reports, contributing to the development of diabetes and obesity.

Zero-calorie sweeteners such as saccharin, sucralose and aspartame, introduced into diets about a century ago, may cause these metabolic changes by altering the population of bacteria in the gut, according to the research.


“The scope of our discovery is cause for a public reassessment of the massive and unsupervised use of artificial sweeteners,” Eran Elinav, a physician and immunologist at Israel's Weizmann Institute of Science and lead author of the study, told the Journal.

These findings might help explain the fact that some studies have found that artificial sweeteners actually contribute to weight gain, even though guidelines published jointly in 2012 by the American Heart Assn. and the American Diabetes Assn. state that artificial sweeteners “when used judiciously … could facilitate reductions in added sugar,” and thus help with weight loss.

The new Nature study analyzes the effects of artificial sweeteners on the workings of the vast colonies of bacteria that inhabit the gut — sometimes called the microbiome. People can have different microbiomes, and will respond differently to what they consume.

In one experiment, the scientists found that mice whose diets included saccharin, sucralose or aspartame had significantly higher blood-glucose levels than mice whose diet included sugar. Saccharin showed the most pronounced effect. 

They next tested 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 microbiomes 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. This suggested that the gut microbes themselves had triggered the higher blood sugar levels in mice fed the fake sweeteners.

To see if the same link was true for people, Elinav and his colleagues looked at the relationship between long-term consumption of artificial sweeteners and various metabolic measurements in 380 nondiabetic people.

They found that the microbiomes of those who regularly ate fake sweeteners were notably different from those who didn't. They also found a correlation between the sweetener consumption and a susceptibility to glucose intolerance.

Artificial sweeteners; Credit: Flickr/Sugar Dish

Artificial sweeteners; Credit: Flickr/Sugar Dish

In the next experiment, seven subjects who normally didn't consume artificial sweeteners were asked to consume products high in the fake sugars. After four days, four of them had significantly higher blood-sugar levels as well as altered gut bacteria – just like the mice.

Researchers aren't sure what exactly causes the imbalance in the gut bacteria populations. But several types of bacteria that changed after the consumption of artificial sweeteners previously have been associated with type 2 diabetes. The results appear to indicate that at least for some people, artificial sweeteners can alter the composition of gut bacteria in such a way that it may contribute to, rather than reduce, certain metabolic conditions related to obesity, such as glucose intolerance.

“Our results link non-calorie artificial sweetener consumption, dysbiosis and metabolic abnormalities, thereby calling for a reassessment of massive NAS usage,” the researchers conclude. “Artificial sweeteners were extensively introduced into our diets with the intention of reducing caloric intake and normalizing blood glucose levels without compromising the human ‘sweet tooth.’ Together with other major shifts that occurred in human nutrition, this increase in NAS consumption coincides with the dramatic increase in the obesity and diabetes epidemics. Our findings suggest that NAS may have directly contributed to enhancing the exact epidemic that they themselves were intended to fight.”

They caution that their results need to be corroborated through a study with many more subjects. However, the outcome certainly raises some big red flags about those little pink packets. 

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