Replacing sugar with artificial sweetener may help your gut microbiome

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

A string of studies in recent years has raised concerns that some low-calorie sweeteners may not be as healthy as they seem. They are a popular option for those trying to keep off weight, but research has found they may stoke hunger, increase blood sugar or raise the risk of heart attacks and strokes. In 2023, the World Health Organization issued guidance advising against using 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. The she and her colleagues recruited 341 adults in Europe who were overweight or had obesity and placed them on a low-calorie diet for two months, leading to an average weight loss of 10 kilograms.

Afterwards, participants followed a healthy diet that included less than 10 per cent 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 individual could use as many types as they wanted.

After 10 months, those in the low-calorie sweetener group maintained a 1.6-kilogram larger weight loss, on average, than the sugar group. They also had a higher 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 sugars in the diet with non-caloric sweeteners may help you in maintaining body weight,” says Blaak. Results from this study may differ from previous ones because of its longer duration, and because it looked at sweeteners being used alongside an otherwise healthy diet, she says. Plus, past 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 at the Weizmann Institute of Science in Israel. So it is difficult to interpret how changes in the group using sweeteners may impact their health, he says, noting it also isn’t clear whether these changes occurred as a result of weight loss, low-calorie sweeteners or both.