Karen Weintraub

Special for USA TODAY

Reaching for artificial sweeteners to avoid sugar may be trading one evil for another, a new study suggests.

For some people, artificial sweeteners may lead to type 2 diabetes as directly as eating sugar does, according to the research, published Wednesday in the journal Nature.

The benefits and risks of artificial sweeteners have been debated for decades. Some studies show no link to diabetes and others suggest there is one. The new research, from the Weizmann Institute of Science in Israel, finds that differences in gut microbes may explain why some people can handle artificial sweeteners just fine while in an unknown percentage of others the sweeteners lead to diabetes.

The human digestive system is home to millions of microbes, largely bacteria, that help digest food and may play a role in health.

The researchers were quick to note that their work needs to be repeated before it's clear whether artificial sweeteners truly can trigger diabetes.

"I think this issue is far from being resolved," said Eran Elinav, who studies the link between an individual's immune system, gut microbes and health at the Weizmann Institute.

He admitted that his research has soured him on sweetening the coffee he needs to get through his day.

"I've consumed very large amounts of coffee and extensively used sweeteners, thinking that they were at least not harmful and perhaps even beneficial," Elinav said at a telephone news conference Tuesday. "Given the surprising result we got in our study, I made a decision to stop using" artificial sweeteners.

George King, chief scientific officer at the Joslin Diabetes Center in Boston, who wrote the forthcoming book The Diabetes Reset, said he may start cutting back on his diet soda habit, too.

"I think I will recommend that people not drink more than one or two cans a day," said King, who was not involved in the new research.

Artificial sweeteners cannot be digested, so it was assumed that there would be no way for them to lead to diabetes. Microbes seem to provide the missing link.

In a series of experiments in mice and people, the researchers examined the interaction between gut microbes and consumption of the sweeteners aspartame, sucralose and saccharine. Depending on the types of microbes they had in their intestines, some people and mice saw a two- to fourfold increase in blood sugars after consuming the artificial sweeteners for a short time. Over time, high blood sugar levels can lead to diabetes.

"The magnitude of the differences were not just a few percentages. These were actually very dramatic differences we saw both in the mice and in the human settings," said Eran Segal, a study co-author who is a computational biologist at the Weizmann Institute.

The study involved several parts:

• A diet study of 400 people found that those who consumed the most artificial sweeteners were more likely to have problems controlling blood sugar.

• Seven people who did not normally consume artificial sweeteners were followed intensively over a week as they were fed controlled amounts of saccharine. Four of the seven showed significant increases in blood sugar levels.

• Mice fed the sweetener saccharine saw dramatic increases in their blood sugar levels.

• Mice with no gut microbes did not see increases in blood sugar levels when they ate artificial sweeteners. Once these bug-free mice were treated with the feces of normal mice that had eaten artificial sweeteners, their blood sugar levels spiked upon eating artificial sweeteners, suggesting that the gut bugs were the driving force in the reaction.

The mouse research in particular was "beautifully performed and elegantly done," said Cathryn Nagler, who researches the connection between gut bugs and food allergies at the University of Chicago and wrote a commentary about the study in Nature. The one piece the study was missing, Nagler said, was an explanation for how different gut bug populations might change someone's ability to process artificial sweeteners.

In trying to understand why certain diseases like food allergies and diabetes have been increasing, Nagler said she looks to things that change gut microbes, such as the introduction of antibiotics, changes in diet, Cesarean-section births, the introduction of formula and the elimination of infectious diseases.

"Now," she said, "I would add artificial sweeteners to this list."