Overview
- The University of Cambridge team published the study in July 2026 and tested 25 gut bacterial species against 39 commercially used sweeteners, finding about three‑quarters changed growth of at least one species.
- Researchers screened sweeteners together with common additives and eight drugs and recorded more than 100 cases where a sweetener's effect shifted, with 34 combinations amplifying effects and 68 reducing them.
- The largest laboratory effect involved the sweetener isosteviol paired with the antidepressant duloxetine, which strongly suppressed Roseburia intestinalis and Parabacteroides merdae, two bacteria linked to metabolic and immune health.
- In a simplified 25‑species synthetic community the isosteviol–duloxetine pair reduced microbial diversity and produced signs of greater toxicity to certain host cells along with altered immune‑related cell activity.
- The authors stress these are in vitro findings that do not prove harm in people and recommend targeted animal and human studies to test real‑world doses, absorption and health outcomes given duloxetine’s wide use.