Non-nutritive sweeteners and the human gut microbiome
What it found
In people, some studies found that non-nutritive sweeteners changed the gut microbiome, and those same studies often found effects on blood sugar.
Other studies found no microbiome changes and no metabolic effects.
What they found
Studies in people
Microbiome changes in people
Of 14 sweetener groups tested in human trials, eight found a significant impact on the gut microbiome, one found limited impact, and five found no significant effect. The type of sweetener did not explain the differences.
Metabolic effects in people
When sweeteners changed the microbiome, studies often also found effects on blood sugar or other metabolic markers. When the microbiome did not change, metabolic markers did not change either.
Observational studies
Seven observational studies found links between non-nutritive sweetener intake and differences in the gut microbiome. These studies used food questionnaires and cannot prove cause and effect.
Animal and lab studies
Lab cultures of gut bacteria
In lab tests using human gut bacteria grown outside the body, sweeteners often increased Enterobacteriaceae and Bifidobacterium. These tests cannot show whether such changes help or harm health.
Studies in people and animals
Personalized responses
Two human trials found that saccharin and sucralose disrupted blood sugar in some people but not others. When gut bacteria from the responders were transplanted into mice, the mice had worse blood sugar control.
Other findings
Unknown sweeteners
No human studies have looked at how allulose, monk fruit, cyclamate, neotame, advantame, or acesulfame-potassium alone affect the gut microbiome.
What the authors conclude
“The limited available data highlight heterogeneity between trials, as some, but not all, find NNS consumption associated with microbiome modulation as well as metabolic effects independent of sweetener type.”
Also in their conclusions
- They say that future trials on the metabolic effects of non-nutritive sweeteners should include microbiome profiling, preferably using shotgun metagenomics.
- They recommend that a personalized nutrition approach may help resolve conflicting reports about non-nutritive sweeteners, the microbiome, and health.
- They call for more research on how non-nutritive sweeteners affect the small intestine microbiome and on under-studied populations.
How it was done
The authors wanted to understand whether non-nutritive sweeteners affect human health through the gut microbiome, since animal studies strongly suggest this link but human trials give mixed results.
They reviewed nine human trials where people were given non-nutritive sweeteners (sucralose, saccharin, stevia, aspartame, or an Ace-K and sucralose blend) and seven observational studies that looked at usual sweetener intake. They also looked at lab studies where human gut bacteria were grown with sweeteners.
What it can’t tell you
- Observational studies can show a link between sweetener intake and microbiome differences, but they cannot prove that sweeteners cause those differences.
- Lab tests on gut bacteria grown outside the body cannot show whether the changes help or harm health in a living person.
- Animal studies cannot show what happens in people, and human trials so far are short and small.
Who paid
- Funding
- Funded by NIH HHS (from the PubMed record).
- Conflicts
- The authors declare that they have no conflicts of interest.
- Authors work at
- Johns Hopkins Bloomberg School of Public Health, USA
The paper
- Title
- Impacts of non-nutritive sweeteners on the human microbiome
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Crakes KR, Questell L, Soni S, Suez J (2025). Impacts of non-nutritive sweeteners on the human microbiome. Immunometabolism (Cobham, Surrey). doi:10.1097/IN9.0000000000000060Free full textPubMed 40291991DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error