Sucralose and Gut Bacteria: New Review of 10 Human Trials

On September 20, 2026, a systematic review and meta-analysis in the International Journal of Molecular Sciences found no statistically significant effect of sucralose on gut microbiome diversity or short-chain fatty acids in healthy adults, across randomized trials lasting one to ten weeks. Fasting glucose and insulin resistance also showed no significant change. The trials were small and short, so the result rules out less than it may seem.

Key takeaways

• No Significant Microbiome Shift: Human clinical trials showed no statistically significant change in gut bacterial alpha diversity (Shannon index SMD = -0.00) or short-chain fatty acids (acetate, propionate, and butyrate).
• Metabolic Markers Unaffected: Pooled data revealed no statistically significant effect on fasting blood glucose (p = 0.88) or homeostatic model assessment of insulin resistance (HOMA-IR, p = 0.212).
• Notable Evidence Limits: The analysis was constrained by low statistical power (5.0% to 19.2%), short intervention windows (none exceeding ten weeks), small study sizes (8 to 61 participants), and varied control comparators.

What happened

On September 20, 2026, an international research team from IPB University in Indonesia and the Warsaw University of Life Sciences in Poland published a systematic review and meta-analysis of randomized controlled trials (RCTs) on sucralose and the human gut microbiota. The authors note that previous meta-analyses included only two human studies. The paper, titled "Effect of Sucralose Consumption on Gut Microbiota: A Systematic Review and Meta-Analysis of Randomized Controlled Trials", appeared in the International Journal of Molecular Sciences (Int. J. Mol. Sci. 2026, 27(18), 8377; DOI 10.3390/ijms27188377; PMID 42794802).

The review was conducted by researchers D. T. Wulandari, N. Andarwulan, Saraswati, E. Palupi, and D. Średnicka-Tober. They set out to test whether sucralose changes gut microbiota composition, alpha diversity, short-chain fatty acid production, or metabolic markers in healthy adults.

The work was financed through statutory funds of the Polish Ministry of Science and Higher Education allocated to the Warsaw University of Life Sciences (SGGW). The open-access article processing charges were supported by an internal SGGW grant (853-2-80-45-780400-S25009). The authors formally declared no competing financial conflicts of interest.

What changed in the scientific evidence on sucralose?

The review pooled human trial evidence only. Following PRISMA guidelines, the authors searched PubMed, Scopus, and Google Scholar in May 2026. From an initial pool of 4,864 identified records, ten randomized controlled trials in healthy adults met the inclusion criteria, and seven trials provided sufficient quantitative data to be pooled in the random-effects meta-analysis.

The trials gave sucralose in doses ranging from 48 mg per day to 780 mg per day over durations spanning one to ten weeks, with most interventions running for less than four weeks. The paper states that about 85% of ingested sucralose reaches the colon unmetabolized, where it can interact directly with gut bacteria. That is why the microbiome question matters.

Pooling the RCT data detailed in the MDPI study record yielded the following specific statistical findings:

• Bacterial Diversity (Shannon Index): Across pooled trials, sucralose exerted no statistically significant effect on bacterial alpha diversity (standardized mean difference [SMD] = -0.00; 95% confidence interval [CI], -1.16 to 1.15; p = 0.99; I2 = 25.67%).
• Fasting Blood Glucose: Sucralose intake did not significantly change fasting blood glucose levels compared to control interventions (SMD = -0.04; 95% CI, -0.63 to 0.56; p = 0.88; I2 = 69.61%).
• Insulin Resistance (HOMA-IR): Meta-analysis of insulin resistance scores revealed no significant alteration (SMD = -0.13; 95% CI, -0.36 to 0.10; p = 0.212; I2 = 0.00%).
• Short-Chain Fatty Acids (SCFAs): Fecal butyrate showed a numerical decrease that did not achieve statistical significance (SMD = -0.42; 95% CI, -13.57 to 12.73; p = 0.76; I2 = 88.10%), derived from only two reporting trials. Acetate (SMD = 1.45; 95% CI, -2.37 to 5.28) and propionate (SMD = 0.66; 95% CI, -3.17 to 4.49) were likewise not significantly altered.
• Bacterial Phyla Ratios: Changes in the Firmicutes-to-Bacteroidetes ratio were documented across several trials but remained largely inconsistent, with only a single included study noting a statistically significant shift.

Risk of bias evaluated via the Cochrane RoB 2.0 tool identified three trials with low risk of bias, four with some concerns, and three with a high risk of bias. The most common methodological weaknesses involved deviations from intended interventions, driven by distinct placebo formulations and challenges in participant blinding.

The authors are clear about the limits. Post hoc statistical power was low, between 5.0% and 19.2%, which leaves open the technical possibility of a type II error (failing to detect a real effect due to small sample sizes). Furthermore, publication bias could not be formally tested because fewer than ten trials were available per individual outcome, and beta diversity (overall community composition) was not pooled.

Who is affected by these gut microbiome findings?

The findings apply to healthy adults, the only group studied. For how sucralose compares with another common sweetener, see Aspartame vs Sucralose: Which Sweetener Is Safer for You?.

The included trials enrolled small sample sizes, ranging from only 8 to 61 participants per study across both intervention and control arms. The total aggregate participant count was not disclosed in the published abstract.

The review covered only healthy adults aged 18 and over, and excluded trials in people with underlying diseases, so it says nothing about:

• Children and adolescents
• Pregnant or lactating individuals
• People living with type 1 or type 2 diabetes
• Patients diagnosed with inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), or related gastrointestinal disorders

The review also excluded studies of sweetener mixtures that did not report sucralose data separately, so blends such as sucralose with acesulfame potassium were not assessed.

What it means for shoppers buying sugar-free products?

For shoppers, the takeaway is modest: in short trials in healthy adults, sucralose did not produce a statistically significant change in gut bacterial diversity or fasting blood sugar. With power as low as 5%, the trials could have missed small effects, and none lasted longer than ten weeks. Real products also differ from the trial conditions:

• No milligram disclosure: United States food labeling regulations do not require manufacturers to disclose the exact milligrams of sucralose per serving on the Nutrition Facts panel; it simply appears in the ingredient list.
• Bulking agents in tabletop packets: Tabletop packets often pair sucralose with maltodextrin or dextrose for volume. The trials tested sucralose, not these carbohydrates, which can raise blood sugar, as detailed in Is Maltodextrin Bad for You? Blood Sugar, Gluten, and Labels.
• Blended sweeteners: Many "zero sugar" drinks and protein products combine sucralose with acesulfame potassium or other sweeteners. Trials of sucralose alone do not tell you about these combinations.

The background

Sucralose, sold under the brand name Splenda, is about 600 times sweeter than table sugar, according to the FDA's sweeteners page. The FDA approved it for 15 food categories in 1998 and as a general-purpose sweetener in 1999, and regulates it as a food additive.

The FDA lists an Acceptable Daily Intake (ADI) for sucralose of 5 mg per kilogram of body weight per day, which works out to about 340 mg a day for a 68 kg adult. The highest dose in the reviewed trials, 780 mg a day, was above that level for most adults.

Sucralose is not the only sweetener getting fresh trial data. For the latest on a plant-derived option, see Does Stevia Spike Insulin? New Trials and an EFSA Reb M Opinion.

What to watch next

The authors conclude that short-term RCTs did not show statistically significant effects, and call for standardized, longer trials with inert comparators.

Key areas to watch include:

• Longer trials: No included study ran beyond ten weeks, so the effect of years of daily use is unknown.
• Inert comparators: The trials compared sucralose with a mix of sugar-free and sugar-containing controls, too few to analyse separately. The authors want standardized, inert comparators.
• Larger trials: With power of 5.0% to 19.2%, bigger studies are needed before a null result can be read as no effect.
• Beta diversity: Overall community composition was not pooled in this review, so shifts in which bacteria are present remain an open question.

This article is not medical advice; ingredient evidence has limitations and individual tolerance varies.