A large laboratory study found that many common sweeteners can directly change the growth of gut bacteria. Researchers identified over 100 instances where sweeteners behaved differently when combined with medications, caffeine, or flavorings. The combination of isosteviol, a sweetener, and the antidepressant duloxetine was particularly disruptive. This combination reduced beneficial bacteria and overall microbial diversity in lab settings.
Sweeteners are present in many everyday products. These include soft drinks, candies, and some medications. They are often marketed as alternatives to sugar with fewer calories. Growing evidence links sweetener consumption to conditions like type two diabetes, obesity, and cancer. The gut microbiome, a community of bacteria in the digestive system, may play a role in these associations.
Researchers at the University of Cambridge tested 39 commercially used sweeteners. They exposed 25 different bacterial species to these sweeteners. About three-quarters of the sweeteners affected the growth of at least one bacterial species. Several sweeteners reduced or stopped the growth of bacteria associated with a healthy digestive system. This suggests that some sweeteners are not biologically inactive substances.
The study also examined how sweeteners interact with other compounds. These included caffeine, vanillin, and eight common drugs. More than 100 cases showed a change in a sweetener's effect when another compound was present. The combined effects became stronger in 34 cases and weaker in 68 cases. This indicates that a sweetener's impact may depend on what else is consumed simultaneously.
The most significant finding involved isosteviol and duloxetine. When combined, these compounds strongly suppressed *Roseburia intestinalis* and *Parabacteroides merdae*. These species are important for gut health and metabolic regulation. The combination also reduced microbial diversity in a simplified microbial community. This suggests potential impacts beyond digestion.
Researchers caution that these experiments were conducted in a laboratory. The findings do not prove that sweeteners cause harm in people. Future studies are needed to determine if similar interactions occur in humans. They also need to assess what doses would be required and if microbial changes produce measurable health effects.
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