Onion extracts and gut bacteria in lab tests
What it found
In lab tests using human stool samples, onion extracts changed the mix of gut bacteria and raised levels of several beneficial compounds.
Onion extracts also helped several Lactobacillus strains grow.
What they found
Animal and lab studies
Gut bacteria mix changed
In lab tests, onion extract lowered the variety of bacteria and shifted the overall bacterial community compared with untreated samples. This happened in both the Bacteroides-dominant and Prevotella-dominant groups.
Helpful bacteria increased
In the Bacteroides-dominant group, bacteria that make short-chain fatty acids, such as Bifidobacterium, Faecalibacterium and Fusicatenibacter, became more common with onion extract. No such increase was seen in the Prevotella-dominant group.
More beneficial metabolites
Short-chain fatty acids like acetate, propionate and butyrate, along with related compounds, rose in the onion-treated samples. Two tryptophan breakdown products, indolelactate and indolepropionate, increased by 4-fold and 32-fold respectively.
Probiotic growth boosted
In lab growth tests, five Lactobacillus strains grew more when onion extract was added to their food. These included L. reuteri, L. rhamnosus, L. plantarum, L. casei and L. fermentum.
What the authors conclude
“These results provide evidence that onion extracts could serve as promising prebiotics by altering gut microbial structure and promoting the production of beneficiary metabolites, including SCFAs and indole derivatives, and enhancing the growth of probiotics.”
Also in their conclusions
- They say onion extract has significant potential as a prebiotic.
- They note that it contains beneficial components, including prebiotic FOS, and that it changes gut bacteria, boosts beneficial metabolites and helps probiotics grow.
- They suggest onion extract could be an effective dietary component for supporting gut health.
How it was done
The authors wanted to see whether onion extracts could act as a prebiotic, meaning a substance that gut bacteria use and that may benefit health.
Stool samples from 19 healthy adults aged 22 to 34 were mixed with onion extract and kept in lab conditions for 24 hours. The team grouped the samples by gut bacterial type and compared the treated samples with untreated ones.
What it can’t tell you
- This was a lab study using stool samples, not people. It cannot show what happens inside the human gut after eating onions.
- The onion extract was not put through a simulation of digestion, so the results may differ from what happens when onions are eaten.
- The Prevotella-dominant group had only 5 people, so the findings for that group are less certain.
Who paid
- Funding
- Funded by MOHW | Korea National Institute of Health (KNIH); National Research Foundation of Korea (NRF) (from the PubMed record).
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Sejong University, South Korea; Dong-A University, Republic of Korea; National Institute of Health, South Korea
The paper
- Title
- The prebiotic potential of dietary onion extracts: shaping gut microbial structures and promoting beneficial metabolites
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Yoo Y, Kim S, Lee W, et al (2025). The prebiotic potential of dietary onion extracts: shaping gut microbial structures and promoting beneficial metabolites. mSystems. doi:10.1128/msystems.01189-24Free full textPubMed 39714164DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error