Sweeteners are often seen as a calorie-free alternative to sugar, found in soft drinks, chewing gums, candies, and even medications, masking bitter tastes. Millions of people unknowingly consume various types of sweeteners daily. Recent research conducted by the University of Cambridge and the European Molecular Biology Laboratory explores the effects of sweeteners when they interact with other substances on gut bacteria.
Sweeteners and Antidepressants: A Notable Combination
The study examined 39 commercially used sweeteners against 25 different bacteria species. Researchers looked at these sweeteners individually and in combination with caffeine, the flavoring agent vanillin, the artificial sweetener advantame, and the antidepressant duloxetine. Strikingly, around three-quarters of the sweeteners altered the growth of at least one bacterial species on their own.
The most significant interaction observed was between the sweetener isosteviol and duloxetine. This combination specifically suppressed two bacterial species, Roseburia intestinalis and Parabacteroides merdae, which are linked with a healthy gut environment and blood sugar regulation. Kiran Patil, the study leader at the MRC Toxicology Unit in Cambridge, emphasized the challenges of isolating the effects of sweeteners from those of other substances, noting that sweeteners are rarely consumed in isolation. Co-author Sonja Blasche pointed out that marketing often paints a simplified picture: “Sweeteners are marketed as metabolism-neutral, but our study challenges this conception.”
Duloxetine is widely prescribed; over 4.2 million patients received prescriptions for it in the U.S. in 2023. Overall, the researchers identified over 100 interactions between sweeteners and the four tested substances. In 34 cases, effects reinforced each other, while in 68, they diminished.
Loss of Bacterial Diversity
Bacteria in the gut do not exist in isolation but as communities. Therefore, the team tested sweeteners on an artificially created bacterial community comprising all 25 species. They found a significant drop in community diversity, shifting the composition favorably towards other species. A high bacterial diversity is generally a sign of a healthy gut, and its decline often correlates with health risks. Persistently lower bacterial diversity could weaken the gut’s resilience to other stress factors, though the study did not explicitly draw this conclusion.
The altered bacterial community also affected human cells in the lab. The secretions from the treated bacterial communities increased cell toxicity towards HeLa cells. Moreover, they changed the secretion of inflammatory mediators interleukin-6 and interleukin-8 by gut cells. Reduced secretion of these mediators could have anti-inflammatory effects, but it may also weaken the defense against pathogens, depending on an individual’s health status.
At the molecular level, the researchers found indications that affected bacteria alter the transport of small molecules across their cell membranes in response to the combination. This adaptation likely contributes to the observed interaction. Patil stated, “Artificial sweeteners are not simply passively excreted by the body but can interact with gut bacteria.”
No Human Evidence Yet
A critical limitation of the study is that experiments were entirely laboratory-based and not conducted on humans. Therefore, the impact of the observed effects on human health remains uncertain. The researchers emphasize the need for further studies to determine whether the observed effects also occur amid individual variations in gut flora.
For consumers, the study offers a crucial insight. Regularly consuming sweeteners alongside medications like duloxetine means ingesting a combination that has been largely unexplored scientifically. This research provides the first systematic lab data on this interaction.
In conclusion, while sweeteners might seem like a harmless alternative to sugar, their interaction with medications and gut bacteria raises important questions about their overall safety and implications for health.
