LONDON, July 16 (Xinhua) -- Commonly used sweeteners can slow or stop the growth of certain gut bacteria in laboratory tests, and their effects may also change when combined with medicines or other widely consumed substances, according to a study released Thursday by the University of Cambridge.
The study, published in the journal Molecular Systems Biology, examined the direct effects of artificial and low-calorie sweeteners on gut bacteria, and how these effects changed when the sweeteners were combined with substances including caffeine, flavorings and medicines.
Researchers grew 25 species of gut bacteria in the laboratory, including beneficial, neutral and potentially harmful species. They exposed each species to 39 commercially used sweeteners, artificial and naturally derived varieties.
About three-quarters of the sweeteners affected the growth of at least one bacterial species. Some slowed or stopped the growth of bacteria associated with a healthy gut, the study found.
The researchers then tested the sweeteners in combination with caffeine, vanillin, another artificial sweetener called advantame and eight commonly used drugs.
They identified more than 100 interactions in which the sweeteners' effects changed when combined with other substances. In 34 cases, the combinations strengthened the effects, while in 68 cases they weakened them.
The most notable interaction involved isosteviol, a sweetener widely used in the food and beverage industry, and the antidepressant duloxetine. The combination strongly suppressed Roseburia intestinalis and Parabacteroides merdae, two gut bacterial species that play important roles in maintaining digestive health.
The researchers also created a synthetic microbial community containing all 25 bacterial species to provide a simplified model of what might happen in the human gut. Further analysis indicated that the combination increased toxicity toward certain host cells and interfered with cells involved in inflammation and immune responses.
"Sweeteners are often marketed as metabolically neutral, but our study challenges this idea," said Sonja Blasche, lead author of the study at the university's Medical Research Council Toxicology Unit.
The researchers stressed that the experiments were conducted in the laboratory and not in humans. Further research is needed before any conclusions can be drawn about the direct effects of sweeteners on human health. ■
