Common sweeteners may disrupt gut health by altering the growth of beneficial bacteria, according to a recent study from the University of Cambridge. Researchers found that around three-quarters of tested sweeteners impacted bacterial growth, with effects often amplified or diminished when combined with medications, food additives, or caffeine.
Laboratory Findings on Sweetener Interactions
Scientists at the Medical Research Council (MRC) Toxicology Unit at the University of Cambridge conducted a series of laboratory tests to observe how 39 common natural and artificial sweeteners affect the human microbiome. By growing 25 distinct species of gut bacteria—representing beneficial, neutral, and potentially harmful strains—researchers measured how these microorganisms multiplied when exposed to various sweeteners.
The results indicated that approximately three-quarters of the sweeteners tested interfered with the growth of at least one bacterial species. In some instances, the sweeteners significantly slowed or halted the proliferation of bacteria essential for a healthy digestive system. These findings suggest that artificial sweeteners do not simply pass through the human body without effect.
The Impact of Combinations: Medications and Additives
A central focus of the study was how sweeteners behave when consumed alongside other substances, such as caffeine, vanillin, and widely used medications. The researchers identified over 100 distinct interactions where the presence of these compounds altered the effects of the sweeteners on gut bacteria. In 34 cases, the combination intensified the inhibitory effects, while in 68 cases, the effects were weakened.
“Our study suggests that artificial sweeteners don’t just pass through the body passively — they can interact with gut microbes, and these effects can be amplified or altered by other substances like medications. These findings can help guide new studies toward understanding how sweeteners might influence health in unexpected ways.”
Professor Kiran Patil, senior author of the study at the MRC Toxicology Unit
One notable interaction involved the sweetener isosteviol and the antidepressant duloxetine. The study found that this specific combination significantly suppressed Roseburia intestinalis and Parabacteroides merdae, two bacteria that play key roles in regulating blood sugar and maintaining gut health. According to the University of Cambridge, over 4.2 million patients in the U.S. were prescribed duloxetine in 2023.
For more on this story, see How Artificial Sweeteners Sabotage Weight Loss and Increase Diabetes Risk.
Synthesizing a Complex Microbiome
To move beyond individual bacterial cultures, the research team created a synthetic community containing all 25 species to better simulate the environment of a human gut. When this community was exposed to various combinations of drugs and sweeteners, the researchers observed a reduction in microbial diversity. A diverse microbiome is widely considered a cornerstone of good digestive health, and its depletion can influence immune responses and inflammation.
“Answering this is further complicated by the fact that we rarely ever take sweeteners by themselves — we take them with drinks, in snacks, or even in medication to mask bitterness.”
Dr. Sonja Blasche, lead author of the study at the MRC Toxicology Unit
While the study provides new insights into the direct interactions between sweeteners and gut bacteria, researchers emphasize that these experiments were conducted in a laboratory setting. Further research is required to determine the real-world implications for human health. The team notes that while sweeteners are often marketed as metabolically neutral, the study challenges this assumption, particularly regarding how they interact with common dietary and medicinal compounds.
If you have concerns about your diet, digestive health, or the potential side effects of medications, consult your healthcare provider.
Sources: Thehill.
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