Artificial sweeteners are a common go-to for diabetes patients, for whom a spoonful of sugar in a coffee or a bowl of oatmeal is off-limits give the no-room-for-error dietary curbs required to manage the disease.

And on that front, a team of University of Cambridge researchers in Britain has some bad news for diabetics: Some “commonly-used sweeteners” likely stall the growth of gut bacteria that are vital for overall health, including one strain that plays a part in managing blood sugar.

In a paper released by the science journal Molecular Systems Biology, the team examined how artificial and low-calorie sweeteners impact gut bacteria and whether the effects change if the sweeteners are swallowed in coffee or medications.

As it turned out, three in four of the 39 sweeteners tested changed how at least one of 25 gut bacteria grew, with effects that included stopping growth in some.

The researchers then tested sweeteners in combination with substances such as coffee, food and medications, finding over 100 cases where they “acted differently”, compared to being used independently. 

“Sweeteners are often marketed as metabolically neutral, but our study challenges this idea,” said study senior author and Cambridge’s MRC Toxicology Unit research director Prof Dr Kiran Patil.

“We found that they can directly affect gut bacteria, particularly when mixed with other compounds such as medication and food additives,” he explained, warning that such “common combinations” have the potential to cause “unintended effects” on the gut microbiome.

The researchers said that combining a compound derived from the widely-used sweetener stevia with anti-depressant drug duloxetine, “strongly suppressed” two bacteria linked to controlling blood sugar and gut health.

The findings add to a growing body of research raising concerns about sweeteners.

In 2025, scientists in Germany and the United States warned that sweeteners could lead to overeating, while a São Paolo-based team flagged potential links to memory loss. – dpa