Cambridge Study Reveals Sweetener Isosteviol Combined with Antidepressant Duloxetine Disrupts Key Gut Bacteria
核心洞察
Cambridge researchers found that isosteviol combined with the antidepressant duloxetine sharply suppressed Roseburia intestinalis (搜索) and Parabacteroides merdae (搜索), two bacteria linked to digestive health and blood sugar regulation.
The study tested 39 sweeteners against 25 gut bacterial species and identified over 100 interactions where sweetener effects changed when combined with other common substances like caffeine, vanillin, or medications.
In a synthetic gut community, the isosteviol-duloxetine combination reduced microbial diversity and increased toxicity toward certain host cells involved in inflammation and immune responses.
A new study from the University of Cambridge has demonstrated that commonly used sweeteners can directly affect gut bacteria, with the most striking effect emerging when the sweetener isosteviol was combined with the widely prescribed antidepressant duloxetine. The combination sharply suppressed two bacterial species considered important for digestive health, blood sugar regulation, and immune function.
The research, published in Molecular Systems Biology, represents one of the first systematic investigations into how artificial and low-calorie sweeteners directly interact with individual gut microbes, particularly when consumed alongside other common substances.
Sweeteners Are Not Simply Passive
Sweeteners are ubiquitous in modern diets, appearing in soft drinks, candy, desserts, breakfast cereals, snacks, and even medications where they mask bitterness. They are commonly promoted as alternatives that provide sweetness with fewer calories. Yet growing evidence has linked sweetener consumption with conditions including type 2 diabetes (搜索), obesity (搜索), and cancer, though these associations do not prove causation.
"Most of what we know about the potential impact of sweeteners on our health comes from animal research or from population studies. While these studies have indicated involvement of the microbiome in mediating the effect of sweeteners, it's difficult to know how sweeteners act in the body — is it through direct interactions with our gut bacteria?" said Professor Kiran Patil from the Medical Research Council (MRC) Toxicology Unit at the University of Cambridge.
Dr. Sonja Blasche, a lead author of the study also from the MRC Toxicology Unit, added: "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."
Systematic Screening Across 39 Sweeteners
The research team grew 25 bacterial species separately in the laboratory, including bacteria considered beneficial, neutral, or potentially harmful. Each species was then exposed to 39 commercially used sweeteners, encompassing both natural and artificial varieties. The researchers monitored how quickly each bacterial culture multiplied and whether its growth slowed or stopped.
Approximately three-quarters of the sweeteners affected the growth of at least one bacterial species. Several reduced or completely halted the growth of bacteria associated with a healthy digestive system, suggesting that some sweeteners are not simply inactive substances that pass through the digestive tract without interacting with the organisms living there.
Over 100 Interactions with Common Compounds
Recognizing that people rarely consume sweeteners in isolation, the researchers paired the sweeteners with substances including caffeine, vanillin (vanilla extract), advantame (an artificial sweetener), and eight commonly used drugs. The team identified more than 100 cases in which a sweetener's effect changed when another compound was present — the combined effects became stronger in 34 cases and weaker in 68 cases.
The most dramatic result involved isosteviol, a sweetener widely used in the food and beverage industry, and duloxetine, an antidepressant prescribed for depression, anxiety, and certain types of chronic pain. In the United States, more than 4.2 million patients received prescriptions for duloxetine in 2023.
When used together, the two compounds strongly suppressed Roseburia intestinalis (搜索) and Parabacteroides merdae (搜索). Both species are considered important members of the gut microbiome and have been linked to digestive health and metabolic regulation.
Impact on a Synthetic Gut Community
To better reflect conditions in the human gut, where microbes constantly interact, the scientists constructed a simplified microbial community containing all 25 bacterial species. They allowed the community to develop and then exposed it to different combinations of sweeteners and drugs, tracking which species became more abundant, which declined, and whether the community retained its overall variety.
The combination of isosteviol and duloxetine reduced microbial diversity within the synthetic community. Greater diversity is generally considered a feature of a resilient and healthy gut microbiome, although the ideal microbial composition can vary between individuals. The combination also changed the community's internal balance by allowing some bacterial species to flourish while others declined.
Additional experiments suggested that these changes increased toxicity toward certain host cells and disrupted the activity of other cells involved in inflammation and immune responses. These results raise the possibility that interactions between sweeteners, medications, and microbes could influence more than digestion alone.
Calls for Human Studies
Dr. Blasche stated: "Sweeteners are often marketed as metabolically neutral, but our study challenges this idea. We found that they can directly affect gut bacteria, particularly when mixed with other compounds such as medication and food additives. These common combinations could have unintended effects on our gut microbiome."
The researchers emphasize that the findings should not be interpreted as proof that sweeteners or the tested combinations cause harm in people. The experiments involved bacteria and cell models under controlled laboratory conditions. In the human digestive system, sweeteners may be absorbed, chemically altered, diluted, or broken down before reaching particular microbes. Diet, genetics, medication use, and the existing composition of a person's microbiome could also change the outcome.
Professor Patil, the study's senior author, concluded: "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 towards understanding how sweeteners might influence health in unexpected ways."
The research was funded by the European Union's Horizon 2020 program and the UK Medical Research Council.