Sweeteners · Metabolic & Cardiometabolic · Gut & Microbiome
saccharin worsens glucose tolerance
Part of: • saccharin
📅 Last reviewed: 2026-07-15 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Human trials (RCT / n-of-1)
How the studies fall
What the evidence shows
Saccharin is the sweetener with the strongest microbiome-mediated glucose-intolerance signal: it was the lead compound in both Suez 2014 (mice + humans) and the Suez 2022 human RCT, where it impaired glycemic responses in susceptible individuals by altering the gut microbiome.
The evidence (10)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Del Pozo et al. 2022 · Nutrients | observational | mixed | low | Review: current evidence indicates saccharin (with sucralose) can influence gut-microbiota composition. |
| Kalin K et al 2026 · study_type: RCT | observational | contradicts | low | 14 overweight non-diabetic adults, 5mg/kg/day saccharin x3mo: no change in clamp-measured insulin sensitivity (ΔM -0.1, P=.85); no change in gut microbiota composition/richness. |
| Suez et al. 2022 · Cell | RCT | supports | high | Human RCT: saccharin impaired glycemic responses via microbiome changes in responsive individuals (lead compound). |
| Conz et al. 2023 · Nutrients | observational | mixed | low | NNS–microbiota review: effects real but heterogeneous and personalized. |
| Pacheco-Sánchez B et al 2025 · study_type: animal | animal | supports | single-lab rat study, mechanistic + outcome combined | Gestational 0.1% saccharin in rats disrupted offspring glucose homeostasis and insulin/GLP-1 signaling in gut-brain axis, sex-dependent effects through adolescence. |
| Ruiz-Ojeda et al. 2019 · Adv Nutr | observational | mixed | low | Review: saccharin among the few sweeteners that measurably change human gut microbiota. |
| Gauthier et al. 2024 · Nutrition | observational | supports | moderate | Human-trial review: saccharin (with sucralose) changed microbiota/glucose tolerance. |
| Suez et al. 2014 · Nature | animal | supports | moderate | Nature: saccharin was the primary non-caloric sweetener inducing glucose intolerance via gut-microbiota changes (mice + human arm). |
| Al-Ishaq et al. 2023 · Nutrients | observational | mixed | low | Sweeteners–microbiome review: saccharin among agents altering microbiota, clinical relevance debated. |
| Rathaus et al. 2024 · Mol Metab | animal | contradicts | moderate | Long-term NNS study: saccharin metabolic effects context-dependent. |
Disagree, or know a study we missed?
We grade by evidence, not opinions. The way to weigh in is to point us to a study we haven't cited (check the evidence table above first), or to flag a problem with one we have. Every submission is reviewed; if it holds up, the grade updates and shows in Science Changes Its Mind.
Opens a short form. You'll sign in with Google so submissions are tied to a real account — we don't display your identity, and we only accept a link we can verify (PubMed, DOI, ClinicalTrials.gov).
Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.