Replacing sugar with artificial sweetener can help your gut microbiome

Using low-calorie sweeteners instead of sugar appears to boost beneficial gut microbes and help people maintain weight loss. The finding, from one of the longest trials of sweeteners to date, indicates that these products may not be as harmful as some studies have suggested.

A number of studies in recent years have raised concerns that some low-calorie sweeteners may not be as healthy as they seem. They’re a popular option for those trying to keep weight off, but research has found they can incite hunger, raise blood sugar, or increase the risk of heart attack and stroke. In 2023, the World Health Organization issued guidance advising against the use of low-calorie sweeteners for weight control.

But long-term studies of sweeteners, especially in the context of a healthy diet, have been lacking. So Ellen Blaak at Maastricht University in the Netherlands tracked their effects in people who used them as a sugar substitute. She and her colleagues recruited 341 adults in Europe who were overweight or obese and put them on a low-calorie diet for two months, which led to an average weight loss of 10 kg.

Afterwards, participants followed a healthy diet that included less than 10 percent of calories from sugar. During this weight maintenance period, 171 of the participants were told to avoid sweeteners altogether, while the rest were encouraged to replace sugary foods and drinks with alternatives made using low-calorie sweeteners. Participants used at least 16 varieties of sweetener, and each could use as many types as they wanted.

After 10 months, those in the low-calorie sweetener group maintained an average weight loss of 1.6 kilograms more than the sugar group. They also had a greater abundance of gut bacteria that produce short-chain fatty acids, beneficial compounds that previous research suggests help regulate blood sugar, support heart health, and promote weight loss and maintenance.

“This shows that at least replacing sugar in the diet with non-caloric sweeteners can help you maintain body weight,” says Blaak. The results from this study may differ from previous ones because of its longer duration and because it looked at sweeteners used alongside an otherwise healthy diet, she says. Plus, previous studies have tended to focus on just a few low-calorie sweeteners, not many of them in tandem.

As for differences in gut bacteria, our understanding of the microbiome is still in its infancy, says Eran Elinav of the Weizmann Institute of Science in Israel. So it’s hard to interpret how changes in the group using sweeteners might affect their health, he says, noting that it’s also not clear whether these changes occurred as a result of weight loss, low-calorie sweeteners, or both.