Aug. 25, 2022 – For years scientists have believed that aspartame and other so-called nonnutritive sweeteners had no effect on the human body. But new research published this month finds that these sugar substitutes can change your gut microbiome in a way that can influence blood sugar levels.

Gut Reaction?

Several years ago, a team led by Eran Elinav, MD, PhD, an immunologist and microbiome researcher at the Weizmann Institute of Science in Israel, found that sugar substitutes affect the microbiome of mice in ways that could affect their blood sugar.

They have now confirmed in a randomized controlled trial with 120 healthy adults.

Before the study, all participants strictly avoided sugar substitutes. During the trial, some continue to avoid them, while others used saccharin, sucralose, aspartame, or stevia daily for 2 weeks in doses lower than the acceptable daily intake.

Each sugar substitute "significantly and distinctly" altered stool and microorganisms in the mouth, and two of the sweeteners (saccharin and sucralose) significantly impacted sugar tolerance, the researchers report.

When researchers transplanted human microbiomes from fecal matter into germ-free mice, they found a link between microbiomes altered by sugar substitutes and sugar tolerance in mice.

The effects of these sweeteners will likely vary from person to person because of the unique make-up of an individual's microbiome.

"We need to raise awareness of the fact that” sugar substitutes do affect the human body, despite what was originally believed, Elinav said in a news release. “With that said, the clinical health implications of the changes they may elicit in humans remain unknown and merit future long-term studies. "

For now, Elinav says it's his personal view that "drinking only water seems to be the best solution."

Weighing the Evidence

Several experts weighed in on the results in a statement from the U.K. nonprofit organization, Science Media Centre.

Duane Mellor, PhD, registered dietitian and senior teaching fellow at Aston University in the UK said the study does not show a link between all sugar substitutes and higher blood sugar levels in the long term.

"It did suggest, though, that some individuals who do not normally consume sweeteners may not tolerate glucose as well after consuming six [packets] of either saccharin or sucralose mixed with glucose per day," Mellor says.

The study does not provide any information about how people who normally consume sweeteners or people with either type 1 or type 2 diabetes respond to these products.

"For some people, it is likely to be a better option and more sustainable approach to use sweeteners as a 'stepping stone,' allowing them to reduce the amount of added sugar in foods and drinks, to reduce their sugar intake, and still enjoy what they eat and drink, on the way to reducing both added sugar and sweeteners in their diet," Mellor said.

Kevin McConway, PhD, with the Open University in the U.K., said , said it's "important to understand that the research is not saying that these sweeteners are worse for us, in heath terms, than sugar.

"But exactly what the health consequences of all this, if any, might be is a subject for future research," McConway adds.