Randomised controlled trialindependent cross-checkabstract checked★ key study I-SOD-106 in-depth review

High-dose saccharin did not change gut bacteria or blood sugar

High-dose saccharin supplementation does not induce gut microbiota changes or glucose intolerance in healthy humans and mice.

Overview

Serrano J et al.. Microbiome 2021 · PMID 33431052 · DOI 10.1186/s40168-020-00976-w

In a placebo-controlled trial, two weeks of saccharin at the maximum acceptable dose changed neither gut bacteria nor glucose tolerance.

Does the study support the specific claim? No · Methodological quality: high

Study explained simply

What did the researchers want to find out?: Test whether saccharin harms gut bacteria and glucose control.
How was the study done?: Double-blind randomised trial in humans plus mouse experiments.
How many people, animals or samples were studied?: Healthy adults; mice.
What was actually found?: No changes in gut bacteria or glucose tolerance.
How large was the observed effect?: No significant differences.
What do the results mean in everyday life?: Effects seen in mice in 2014 were not confirmed for saccharin in this trial.
What are the study's limitations?: Short trial; capsules.
What does it say about Elawady's specific claim?: Contradicts the claim for saccharin.
Do the results apply to Germany and Europe?: Applicable.
What can explicitly not be concluded from this study?: Cannot rule out effects in some individuals or over years.

Authors: Serrano J et al.
Journal: Microbiome
Year: 2021
Identifier: PMID 33431052 DOI 10.1186/s40168-020-00976-w
Verification: verified – PubMed efetch 2026-10-26 + Crossref 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: NIH (NIDDK, NIAID) grants; authors declare no competing interests (PubMed record)

Does pure saccharin at the maximum acceptable daily intake alter gut microbiota or glucose tolerance?

Study design: Randomised controlled trial – Double-blind, placebo-controlled, parallel-arm RCT in humans (2 weeks) plus 10-week mouse study; NCT03032640
Population: Healthy men and women; chow-fed wild-type and sweet-receptor knockout mice
Country: USA
Period: Registered 2017
Sample size: Not stated in abstract (four human arms)
Inclusion and exclusion criteria: Healthy adults; details in full text

Exposure / intervention: Saccharin capsules twice daily at maximum ADI; lactisole; saccharin plus lactisole
Comparator: Placebo
Endpoints: OGTT glucose and hormones; microbiome diversity and composition; faecal metabolites; SCFA
Statistical methods: Between-arm comparisons

Results: In humans and mice, no intervention affected glucose or hormonal responses to an OGTT. Pure saccharin did not alter microbial diversity or composition at any taxonomic level; no effects on faecal metabolites or SCFA.
Absolute risks: not applicable
Authors' conclusion: Short-term saccharin consumption at maximum acceptable levels is not sufficient to alter gut microbiota or induce glucose intolerance in apparently healthy humans and mice.

Null result in a small trial cannot exclude person-specific effects as described by Suez 2022 (I-SOD-03).

Directly contradicts C-SOD-07 for saccharin: no microbiome change and no glucose intolerance.

Suez 2022 (I-SOD-03): saccharin and sucralose impaired glycaemic responses in a 120-person RCT.

Applicable.

High-quality null trial that conflicts with Suez 2014/2022; human evidence is inconsistent.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	high
Risk of bias	low
Precision of results	low
Directness	direct
Reproducibility	not replicated
Consistency with the overall evidence	inconsistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Reasons for discordance (vehicle, baseline microbiome, dose form).