Artificial sweeteners might be triggering higher blood sugar levels in some people and contributing to the problems they were designed to combat, such as diabetes and obesity, according to new findings published Wednesday in the journal Nature.

Although the precise reasons behind the blood sugar changes remain uncertain, researchers suspect that artificial sweeteners could be disrupting the microbiome, a vast and enigmatic ecosystem of bacteria in our guts.

In a series of experiments, researchers found that several of the most widely used types of non-calorie sweeteners in food and drinks – saccharin, sucralose and aspartame – caused mice to experience increased risk of glucose intolerance, a condition that can lead to diabetes.

“We are talking about very dramatic increases,” said one of the study’s co-authors, Eran Segal, a computational biologist at the Weizmann Institute of Science in Israel.

The same scientists also monitored what happened to seven human volunteers who did not typically use artificial sweeteners but were given regular doses of saccharin over the course of a week. Four developed significant glucose intolerance, and the others saw no blood sugar benefits from using artificial sweeteners. Separately, the researchers analyzed nearly 400 people and found that the gut bacteria of those who used artificial sweeteners was noticeably different from people who did not.

Wednesday’s findings add an intriguing new dimension to the long-running, contentious debate over the potential health benefits and risks of artificial sweeteners, which are among the most common food additives.