Study analysis · Foods · 2026
Vegetarian women have 3x more of this rare gut bacteria—and it’s hiding in their pickled veggies.
Women who eat plants and fermented foods like pickled soy paste have gut bugs that make more healthy chemicals than meat-eaters.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study looked at what bacteria and chemicals were in the poop of women who ate mostly plants and those who ate meat. It found differences, but it didn’t change anyone’s diet to see if that caused the changes. So it’s like noticing that people who ride bikes often have stronger legs — but we don’t know if biking made their legs strong, or if strong-legged people just like biking.
What’s the bottom line?
Women who eat mostly plants and daily fermented foods like pickled veggies and soy paste have different gut bacteria than women who eat meat. These plant-eating women’s gut bugs make more good chemicals that help their intestines and give them more nutrients.
How strong is this study?
The scientists used good tools to count the bacteria and measure chemicals, and they tried to be fair by comparing similar women. But they only looked at 32 people, all from one place, and didn’t change anything — so we can’t be super sure the results apply to everyone. It’s a good snapshot, but not a full experiment.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
34 / 100
- Randomizationnot randomized
- Blinding+9/15
- Control group+15/15
- Sample size (n=32)+3.0/20
- Follow-upno follow-up reported
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. This is a cross-sectional observational study with no randomization or intervention; it measures associations at a single time point and cannot determine whether diet causes changes in gut microbiota or vice versa.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding sources were disclosed in the text; study appears independently conducted with no industry ties evident.
Independent Analysis Safeguards
- Study was conducted in a single-blind manner
- Participants were assigned identification numbers
- All analyses were performed using anonymized datasets
- Research protocol approved by Chulalongkorn University Ethics Committee
- Study registered with Thai Clinical Trial Registry
No conflict of interest statement or funding disclosure was provided in the text. While the methods describe rigorous protocols and ethical oversight, the absence of a funding declaration introduces uncertainty. However, no industry affiliations, employment ties, or financial relationships are mentioned among authors or institutions. The study appears academically driven with no evidence of industry influence.
Key takeaways
- 01
Vegetarian women had 3x more Weissella bacteria and 2x higher levels of SCFAs (like butyrate) in their poop than meat-eating women.
- 02
Their fermented foods also had more amino acids and SCFAs.
- 03
Yes — higher SCFAs mean better gut lining and less inflammation; more amino acids help make up for nutrients often low in plant diets.
Surprising findings
- Weissella, a bacterium rarely seen in adult human guts, was uniquely enriched in vegetarians and directly linked to fermented food intake.Most people assume gut bacteria come from birth or long-term colonization—but this suggests daily fermented food consumption can introduce transient but beneficial microbes that stick around long enough to matter.
- Fermented plant foods produced more essential amino acids than fermented animal foods.Animal products are assumed to be superior protein sources—but here, fermented soy and mushrooms outperformed fermented fish and kefir in amino acid content.
Practical takeaways
Add 1–2 servings of traditional fermented plant foods daily—like pickled mushrooms, soy paste, or fermented rice—to boost gut SCFAs and essential amino acids.
This study only looked at Thai postmenopausal women; results may vary by age, ethnicity, or baseline diet. Also, fermented foods aren’t a magic bullet for nutrient deficiencies.
medium confidenceWhy this study matters
Weissella: The Secret Gut Hero
Vegetarian women had 3x higher levels of Weissella bacteria compared to omnivores, a genus rarely found in adult guts. This bacterium was directly linked to daily consumption of fermented foods like sour mushrooms and soy paste, and was absent in omnivores.
Weissella isn’t a typical gut bacterium—it’s usually found in fermented foods. This suggests eating fermented veggies might be literally seeding your gut with new, beneficial microbes.
SCFAs: The Gut’s Superfuel
Vegetarians produced 2x higher levels of short-chain fatty acids (SCFAs) like butyrate and propionate—key compounds that feed the gut lining and reduce inflammation. These were directly tied to daily fermented food intake and plant fiber.
Butyrate is called the 'gold standard' for gut health. This study shows plant-based eaters aren’t just avoiding meat—they’re actively fueling their intestines with natural anti-inflammatory chemicals.
Fermented Foods = Nutrient Boosters
Fermented plant foods like salty soy paste (FVG-6) contained higher levels of essential amino acids (leucine, lysine, threonine) than animal-based fermented foods. These amino acids are often low in vegetarian diets.
Plant diets are often criticized for lacking complete protein—but this study shows fermentation can turn soy and mushrooms into amino acid powerhouses, naturally.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Women who eat mostly plants and daily fermented foods like pickled veggies and soy paste have different gut bacteria than women who eat meat. These plant-eating women’s gut bugs make more good chemicals that help their intestines and give them more nutrients.
Research results
Vegetarian women had 3x more Weissella bacteria and 2x higher levels of SCFAs (like butyrate) in their poop than meat-eating women. Their fermented foods also had more amino acids and SCFAs.
What this means - more context
Yes — higher SCFAs mean better gut lining and less inflammation; more amino acids help make up for nutrients often low in plant diets.
This study investigates how long-term vegetarian versus omnivorous diets, combined with fermented food intake, shape gut microbiota and fecal metabolome profiles in healthy postmenopausal Thai women.
Vegetarians showed enriched Prevotella, Faecalibacterium, Blautia, and Weissella, with higher SCFA production and amino acid levels, while omnivores had higher Bacteroides, Escherichia–Shigella, and protein catabolism markers. Fermented foods consumed by vegetarians contained matching microbes and metabolites, suggesting a dietary contribution to gut health.
Methods Used
Observational cross-sectional study of 32 healthy postmenopausal Thai women (16 vegetarians, 16 omnivores). Gut microbiota was analyzed via 16S rRNA metagenomics; fecal metabolomes via untargeted 1H-NMR. Fermented food samples were microbiologically and metabolically characterized.
Main Finding
Vegetarians exhibited significantly higher gut abundance of Prevotella, Faecalibacterium, Blautia, and Weissella, with enhanced carbohydrate fermentation and SCFA production (acetate, propionate, butyrate) and elevated essential amino acids in feces and fermented foods, compared to omnivores who showed greater protein catabolism signatures.
Confidence Level
Moderate. Findings are supported by robust metabolomic and metagenomic methods, statistical significance (p < 0.05), and effect size reporting. However, cross-sectional design, small sample size (n=32), and lack of causal inference limit confidence.
Study Flags
Red Flags
- •Cross-sectional design — cannot prove causation
- •Small sample size (n=32) limits generalizability
- •No control for all dietary variables beyond vegetarian/omnivore status
Surprising Findings
Weissella, a bacterium rarely seen in adult human guts, was uniquely enriched in vegetarians and directly linked to fermented food intake.
Most people assume gut bacteria come from birth or long-term colonization—but this suggests daily fermented food consumption can introduce transient but beneficial microbes that stick around long enough to matter.
Practical Takeaways
Add 1–2 servings of traditional fermented plant foods daily—like pickled mushrooms, soy paste, or fermented rice—to boost gut SCFAs and essential amino acids.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at what bacteria and chemicals were in the poop of women who ate mostly plants and those who ate meat. It found differences, but it didn’t change anyone’s diet to see if that caused the changes. So it’s like noticing that people who ride bikes often have stronger legs — but we don’t know if biking made their legs strong, or if strong-legged people just like biking.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Use of validated metagenomic (16S rRNA) and metabolomic (NMR) techniques
- Detailed characterization of both gut microbiota and fermented food microbiota
- Statistical power calculation performed a priori
Weaknesses
- Cross-sectional design prevents causal inference
- No control for confounding variables (e.g., physical activity, medication history beyond exclusion criteria)
- 16S rRNA sequencing cannot resolve species-level or functional activity directly
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Women who eat mostly plants and daily fermented foods like pickled veggies and soy paste have different gut bacteria than women who eat meat. These plant-eating women’s gut bugs make more good chemicals that help their intestines and give them more nutrients.
Research results
Vegetarian women had 3x more Weissella bacteria and 2x higher levels of SCFAs (like butyrate) in their poop than meat-eating women. Their fermented foods also had more amino acids and SCFAs.
What this means - more context
Yes — higher SCFAs mean better gut lining and less inflammation; more amino acids help make up for nutrients often low in plant diets.
This study investigates how long-term vegetarian versus omnivorous diets, combined with fermented food intake, shape gut microbiota and fecal metabolome profiles in healthy postmenopausal Thai women.
Vegetarians showed enriched Prevotella, Faecalibacterium, Blautia, and Weissella, with higher SCFA production and amino acid levels, while omnivores had higher Bacteroides, Escherichia–Shigella, and protein catabolism markers. Fermented foods consumed by vegetarians contained matching microbes and metabolites, suggesting a dietary contribution to gut health.
Methods Used
Observational cross-sectional study of 32 healthy postmenopausal Thai women (16 vegetarians, 16 omnivores). Gut microbiota was analyzed via 16S rRNA metagenomics; fecal metabolomes via untargeted 1H-NMR. Fermented food samples were microbiologically and metabolically characterized.
Main Finding
Vegetarians exhibited significantly higher gut abundance of Prevotella, Faecalibacterium, Blautia, and Weissella, with enhanced carbohydrate fermentation and SCFA production (acetate, propionate, butyrate) and elevated essential amino acids in feces and fermented foods, compared to omnivores who showed greater protein catabolism signatures.
Confidence Level
Moderate. Findings are supported by robust metabolomic and metagenomic methods, statistical significance (p < 0.05), and effect size reporting. However, cross-sectional design, small sample size (n=32), and lack of causal inference limit confidence.
Study Flags
Red Flags
- •Cross-sectional design — cannot prove causation
- •Small sample size (n=32) limits generalizability
- •No control for all dietary variables beyond vegetarian/omnivore status
Surprising Findings
Weissella, a bacterium rarely seen in adult human guts, was uniquely enriched in vegetarians and directly linked to fermented food intake.
Most people assume gut bacteria come from birth or long-term colonization—but this suggests daily fermented food consumption can introduce transient but beneficial microbes that stick around long enough to matter.
Practical Takeaways
Add 1–2 servings of traditional fermented plant foods daily—like pickled mushrooms, soy paste, or fermented rice—to boost gut SCFAs and essential amino acids.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at what bacteria and chemicals were in the poop of women who ate mostly plants and those who ate meat. It found differences, but it didn’t change anyone’s diet to see if that caused the changes. So it’s like noticing that people who ride bikes often have stronger legs — but we don’t know if biking made their legs strong, or if strong-legged people just like biking.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Use of validated metagenomic (16S rRNA) and metabolomic (NMR) techniques
- Detailed characterization of both gut microbiota and fermented food microbiota
- Statistical power calculation performed a priori
Weaknesses
- Cross-sectional design prevents causal inference
- No control for confounding variables (e.g., physical activity, medication history beyond exclusion criteria)
- 16S rRNA sequencing cannot resolve species-level or functional activity directly
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The scientists used good tools to count the bacteria and measure chemicals, and they tried to be fair by comparing similar women. But they only looked at 32 people, all from one place, and didn’t change anything — so we can’t be super sure the results apply to everyone. It’s a good snapshot, but not a full experiment.
0 / 100
- COI disclosureconflicts of interest not disclosed
- Data availabilitydata not shared
- Code availabilitycode not shared
34 / 100
- Randomizationnot randomized
- Blinding+9/15
- Control group+15/15
- Sample size (n=32)+3.0/20
- Follow-upno follow-up reported
100 / 100
100 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registration+15/15
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. This is a cross-sectional observational study with no randomization or intervention; it measures associations at a single time point and cannot determine whether diet causes changes in gut microbiota or vice versa.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding sources were disclosed in the text; study appears independently conducted with no industry ties evident.
Independent Analysis Safeguards
- Study was conducted in a single-blind manner
- Participants were assigned identification numbers
- All analyses were performed using anonymized datasets
- Research protocol approved by Chulalongkorn University Ethics Committee
- Study registered with Thai Clinical Trial Registry
No conflict of interest statement or funding disclosure was provided in the text. While the methods describe rigorous protocols and ethical oversight, the absence of a funding declaration introduces uncertainty. However, no industry affiliations, employment ties, or financial relationships are mentioned among authors or institutions. The study appears academically driven with no evidence of industry influence.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from Nutrition Made Simple! cite this study, drawing 1 claim from it.
- Strong evidence
At least some randomized or controlled trials support this claim.
Evidence
Authored by
7 researchersIf this is your work, this is how we attribute it on Fit Body Science. Natthanan Buranavanitvong is listed as the lead author.