A 2024 Science paper shows that industrialised humans have lost the cellulose-degrading gut bacteria, so the modern human gut 'was never built to digest cellulose' and no longer carries the machinery to ferment plant cell walls.
Original statement
No Arabic original wording available.
Translation
A 2024 Science paper shows that industrialised humans have lost the cellulose-degrading gut bacteria, so the modern human gut 'was never built to digest cellulose' and no longer carries the machinery to ferment plant cell walls.
Origin
- Source status
- Archive editors
- Attribution
- Archive editors
- Origin
- https://eltayebat.com/rule/leafy-greens-cucurbits/
- Attribution uncertainty
- Archive featured card and narrative on Moraïs et al. 2024; presented as 'the deepest support for Dr. Diaa's ruminant argument'.
- Claimed mechanism
Loss of cellulosome-producing Ruminococcus species.
- Claimed health effect
Inability to ferment plant cell walls.
- Population concerned
Industrialised populations
- Geographic restriction by Elawady
none found
Scientific assessment
Mostly false – Essential parts of the statement are not supported by the evidence or are strongly exaggerated.
Certainty of evidence: moderate – Further research may still affect the assessment.
1. What was claimed?
Modern humans lack microbes to ferment cellulose, so vegetables are the wrong fuel.
2. What is demonstrably correct?
Correctly reported: cellulosome-producing ruminococci are abundant in hunter-gatherers, rural and ancient populations and rare in industrialised societies; one species likely came from ruminants.
3. What is wrong or exaggerated?
The paper is titled 'Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans', i.e. such bacteria exist in industrialised humans, although rarely. Cellulose is only one component of plant fibre; pectins, hemicelluloses, inulin and resistant starch are fermented by many common gut bacteria. The paper says nothing about vegetables being harmful. The authors report these species in at most 4.6% of industrialised samples versus about 20-43% in non-industrialised and ancient samples, attribute their rarity to the westernised lifestyle, and suggest re-introducing them through targeted diets and specialised probiotics - the opposite of the inference that humans are not built to digest plant fibre. If anything, the authors interpret the loss as a consequence of the westernised lifestyle, which suggests that higher plant-fibre intake supports these microbes.
4. What remains unclear?
Whether low abundance of cellulose degraders has health consequences is unknown.
5. Which studies support it?
None for the archive's conclusion.
6. Which studies contradict it?
Moraïs 2024 abstract itself; controlled feeding studies in US adults showing 42-70% apparent digestion of cellulose from fruits and vegetables (Slavin 1981, I-VEG-129; Kelsay 1981, I-VEG-130); microbes degrading spinach cell walls found in all French volunteers tested (Chassard 2010, I-VEG-131); Koh 2016; Reynolds 2019.
7. What applies to Germany and Europe?
Applies to industrialised populations including Germany.
8. What is known about Egypt?
Not specific.
9. What practical conclusion is appropriate?
The study is about microbiome ecology; it does not support avoiding vegetables.
Assessment details
- Rationale for certainty of evidence
The paper's abstract states that humans, like all mammals, depend on the gut microbiome for cellulose digestion and that cellulose-degrading species are present but rare in industrialised populations; it does not show that the gut cannot ferment other plant cell-wall fibres, and it does not study health effects of eating vegetables.
- Source quality
High-quality basic-science paper; archive interpretation goes beyond the findings.
- Regional transferability
The finding concerns industrialised populations (including Germany); rural Egyptian populations were not specifically mentioned in the abstract.
- Individual exceptions
Not applicable.
- Regional scope of the claim
- not specified
- Last reviewed
- 26 October 2026 provisional
Scientific evidence in detail
Scientifically refuted – High-quality evidence shows the opposite, or the claim contradicts well-established physiology.
Research question: Does the 2024 Science paper (Moraïs et al.) show that industrialised humans lack the microbial machinery to ferment cellulose and plant cell walls?
Research question in detail (PECO)
- Population
- Industrialised human populations
- Intervention or exposure
- Industrialised lifestyle / low-fibre diet
- Comparison
- Non-industrialised and ancient populations
- Geographic scope
- universal biology; microbiome composition varies with lifestyle
- Outcomes
- presence of cellulose-degrading microbes
- fermentation of plant cell walls
Study results as reported by the authors. Our assessment follows below.
What speaks for the claim?
Cellulose-digesting gut bacteria
Moraïs S et al.. Science 2024 · PMID 38484069 · DOI 10.1126/science.adj9223 Otherfull text, structured risk-of-bias assessmentMoraïs 2024 (Science), full text in register.
- Actual result
- Cellulosome-producing ruminococci in at most 4.6% of industrialised samples vs 20-43% in rural, hunter-gatherer and ancient samples.
- Methodological quality
- high (large metagenomic analysis + biochemistry)
- Relevance
- direct for the "rare in industrialised people" part only
- Limitations
- Does not test fermentation capacity of the whole microbiome or health effects.
What speaks against the claim?
Every person tested had gut microbes that break down spinach cell walls
Chassard C et al.. FEMS Microbiol Ecol 2010 · PMID 20662929 · DOI 10.1111/j.1574-6941.2010.00941.x Otherabstract checkednewly addedChassard 2010: culture and qPCR of human faecal cellulose degraders.
- Actual result
- Spinach cell-wall degrading microorganisms present in all individuals (French volunteers); taxa differ by methane status.
- Methodological quality
- moderate
- Relevance
- direct
- Limitations
- Small lab study.
Humans ferment much of the cellulose in vegetables
Slavin JL et al.. J Nutr 1981 · PMID 6257867 · DOI 10.1093/jn/111.2.287 Otherabstract checkednewly addedSlavin 1981 controlled feeding (US).
- Actual result
- ~70% of cellulose from a mixed fruit/vegetable diet disappeared.
- Methodological quality
- moderate
- Relevance
- direct
- Limitations
- n = 7.
Cellulose-digesting gut bacteria
Moraïs S et al.. Science 2024 · PMID 38484069 · DOI 10.1126/science.adj9223 Otherfull text, structured risk-of-bias assessmentThe archive's own source.
- Actual result
- Title and abstract describe cellulose degraders IN industrialised humans; authors attribute rarity to westernised low-fibre lifestyle and suggest restoring them via diet.
- Methodological quality
- high
- Relevance
- direct
- Limitations
- n/a
What does the overall evidence say?
Editorial assessment based on the studies above – not itself a study result.
Which position is better supported?
Cellulosome-producing ruminococci have become rare in industrialised populations, but other cellulose and cell-wall degraders (e.g. Bacteroidetes) are present, and controlled feeding studies show substantial fermentation of vegetable cellulose in industrialised adults.
Why some studies weigh more
The archive's source is high quality but answers a narrower question (prevalence of one bacterial group); direct fermentation and culture studies answer the claim's question.
Is a causal relationship established? Not applicable Interpretation claim about a study.
Remaining uncertainty
Health consequences of losing cellulosome-producing ruminococci.
Justified conclusion
The archive correctly reports the rarity finding but draws the wrong conclusion; the paper and other studies show that modern human guts still ferment plant cell walls.
Why do studies seem to disagree?
Moraïs 2024 (rarity of one bacterial group) and Slavin/Kelsay/Chassard (fermentation occurs) answer different questions and are compatible.
Does this depend on the country?
- General biological effects
- Microbiome capacity differs by lifestyle, not by a fixed human design.
- Eating habits
- Higher-fibre traditional diets support fibre-degrading microbes.
- Origin of the food
- not applicable
- Contaminants
- not applicable
- National production conditions
- not applicable
- Legal rules
- not applicable
- Actual monitoring data
- not applicable
A regional difference that changes the conclusion is not supported by robust data.
Statistical re-check
- Cellulose fermented per day in industrialised adults – ~3.8 g/day (69.7% of 5.4 g). recalculated
Certainty of the overall evidence (GRADE, simplified)
- Main outcome
- Capacity of industrialised human gut to ferment plant cell walls
- Starting level
- low (observational studies)
- Reasons for downgrading
- imprecision
- Reasons for upgrading
- consistency across feeding studies and microbiology
- Result
- moderate
Simplified assessment by a single reviewer, following the GRADE approach; not a formal GRADE panel. GRADE rates the body of evidence for one outcome, not individual studies.
Search strategy
Documented literature searches for this review (search strings in the original database syntax).
| Database | Date | Search | Looking for | Hits | Included |
|---|---|---|---|---|---|
| PubMed | 26 October 2026 | (cellulose) AND (human OR humans) AND (colon* OR fecal OR faecal OR gut) AND (degrad* OR digestib* OR ferment*) AND (Ruminococcus OR methanogen* OR "cellulolytic") | both directions | 46 |
Open questions
Whether reintroducing cellulolytic ruminococci has health effects.
How deeply was this checked?
6 linked studies: 1 checked in full text (1 of them with a structured risk-of-bias assessment), 5 on the basis of the abstract, 0 bibliographically only. No formal assessment with two independent reviewers and no independent human expert review has taken place yet.
Last scientific review: 26 October 2026
History of the verdict
- 25 October 2026 · Phase 1 · Initial assessment: Mostly false (moderate)
- 26 October 2026 · Phase 4 (systematic evidence review) · Re-examined with extended evidence; verdict unchanged: Mostly false (moderate)
Direct human fermentation data strengthen the existing conclusion; the archive reproduces the rarity finding correctly, which keeps the verdict at “Mostly false” rather than “False”.
New sources: I-VEG-129 I-VEG-130 I-VEG-131
In plain language
The archive cites a 2024 study as proof that modern humans cannot digest plant fibre. The study actually found cellulose-digesting bacteria in humans, common in traditional and rural populations and rare in industrialised ones. It did not test whether eating vegetables is harmful. Many other fibre types in vegetables are fermented by common gut bacteria, and the loss of these microbes may itself reflect low-fibre western diets.
Studies on this claim
Studies supporting the claim (0)
No studies in this group.
Studies contradicting or limiting the claim (5)
-
How gut bacteria use fibre
Koh A et al.. Cell 2016 · PMID 27259147 · DOI 10.1016/j.cell.2016.05.041Narrative reviewindependent cross-checkabstract checkedGut bacteria turn fibre into short-chain fatty acids that act as fuel and signals for the body.
Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Explain SCFAs
- How was the study done?
Review
- How many people, animals or samples were studied?
Not applicable
- What was actually found?
SCFAs act on host physiology
- How large was the observed effect?
Not applicable
- What do the results mean in everyday life?
Fibre feeds beneficial processes.
- What are the study's limitations?
Mechanistic
- What does it say about Elawady's specific claim?
Contradicts 'useless cellulose'
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Cannot quantify clinical benefit.
-
Fibre and health (Lancet 2019)
Reynolds A et al.. Lancet 2019 · PMID 30638909 · DOI 10.1016/S0140-6736(18)31809-9Meta-analysisindependent cross-checkabstract checked★ key studyHigh fibre intake is linked to 15-30% lower death and disease rates; trials show better weight, blood pressure and cholesterol.
Does the study support the specific claim? No · Methodological quality: high · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Fibre and NCDs
- How was the study done?
Meta-analyses
- How many people, animals or samples were studied?
185 cohorts, 58 RCTs
- What was actually found?
Large benefits
- How large was the observed effect?
15-30% lower risk
- What do the results mean in everyday life?
Eat 25-29 g fibre daily.
- What are the study's limitations?
Observational endpoints
- What does it say about Elawady's specific claim?
Contradicts 'cattle food'
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Not specific to leafy greens.
-
Humans ferment much of the cellulose in vegetables
Slavin JL et al.. J Nutr 1981 · PMID 6257867 · DOI 10.1093/jn/111.2.287Otherindependent cross-checkabstract checked★ key studyIn 7 women on controlled diets, about 70% of cellulose from fruits and vegetables was broken down in the gut, but only 8-16% of purified cellulose.
Industrialised (US) adults fermented most vegetable cellulose.
Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Measure fibre digestibility in humans.
- How was the study done?
Controlled feeding.
- How many people, animals or samples were studied?
7 women.
- What was actually found?
Plant-food cellulose ~70% digested; purified cellulose little.
- How large was the observed effect?
69.7% vs 15.7%.
- What do the results mean in everyday life?
Gut bacteria break down much of the cellulose in vegetables.
- What are the study's limitations?
Very small; old methods.
- What does it say about Elawady's specific claim?
Contradicts the claim.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot measure health effects.
-
Vegetable cellulose partly broken down in men
Kelsay JL et al.. Am J Clin Nutr 1981 · PMID 6269418 · DOI 10.1093/ajcn/34.9.1849Otherindependent cross-checkabstract checked★ key studyIn 12 men eating fruits and vegetables, 42% of cellulose and 88% of hemicellulose were broken down in the gut.
Industrialised adults fermented a substantial share of vegetable cellulose.
Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Measure fibre fractions' digestibility.
- How was the study done?
Controlled feeding.
- How many people, animals or samples were studied?
12 men.
- What was actually found?
Cellulose 42%, hemicellulose 88%.
- How large was the observed effect?
See results.
- What do the results mean in everyday life?
Gut microbes use a large part of vegetable fibre.
- What are the study's limitations?
Small; old methods.
- What does it say about Elawady's specific claim?
Contradicts the claim.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot measure health effects.
-
Every person tested had gut microbes that break down spinach cell walls
Chassard C et al.. FEMS Microbiol Ecol 2010 · PMID 20662929 · DOI 10.1111/j.1574-6941.2010.00941.xOtherindependent cross-checkabstract checkedFrench researchers found bacteria able to degrade spinach cell walls in all volunteers, of different types depending on methane production.
Spinach cell-wall degraders found in all individuals; different taxa by methane status.
Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Characterise human cellulose degraders.
- How was the study done?
Culture and PCR.
- How many people, animals or samples were studied?
Volunteers (n not in abstract).
- What was actually found?
Degraders present in all.
- How large was the observed effect?
Not applicable.
- What do the results mean in everyday life?
Modern European guts can ferment vegetable cell walls.
- What are the study's limitations?
Small lab study.
- What does it say about Elawady's specific claim?
Contradicts the claim.
- Do the results apply to Germany and Europe?
European.
- What can explicitly not be concluded from this study?
Cannot quantify fermentation in vivo.
No study in this group is marked as key.
Studies with mixed or unclear results (1)
-
Cellulose-digesting gut bacteria
Moraïs S et al.. Science 2024 · PMID 38484069 · DOI 10.1126/science.adj9223Othercited by the Tayebat archivefull text, structured risk-of-bias assessment★ key studyHumans carry cellulose-digesting bacteria; they are common in traditional populations and rare in industrialised ones.
Does the study support the specific claim? No · Methodological quality: high · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Map cellulose degraders
- How was the study done?
Metagenomics + biochemistry
- How many people, animals or samples were studied?
Not stated
- What was actually found?
Rare in industrialised humans
- How large was the observed effect?
Not applicable
- What do the results mean in everyday life?
Western lifestyle may reduce these microbes.
- What are the study's limitations?
No health data
- What does it say about Elawady's specific claim?
Does not support avoiding vegetables
- Do the results apply to Germany and Europe?
Moderate
- What can explicitly not be concluded from this study?
Cannot show vegetables are harmful.
No study in this group is marked as key.
Regional context
Germany / EU
Applies to industrialised populations including Germany.
Egypt
Not specific.
What applies in my country?
General scientific assessment
Mostly false The study is misread: it documents rare, not absent, cellulose degraders, and other studies show that modern human gut microbes still ferment much of the cellulose in vegetables.
The following areas of food safety are relevant to this statement:
- Pesticides and pesticide residues
- Contaminants (heavy metals, PFAS, PCBs, dioxins, nitrate)
- Pathogens (Salmonella, Campylobacter, etc.)
Fruit and vegetables
Choose a country to see the checked information for it.
Limits: legal rules describe what is allowed, not what every single food contains. Measurement data come from samples and are meaningful only together with their method details.
Country of residence or purchase Compare with another country
References
- From Dietary Fiber to Host Physiology: Short-Chain Fatty Acids as Key Bacterial Metabolites.. Koh A et al.. Cell 2016 · PMID 27259147 · DOI 10.1016/j.cell.2016.05.041
- Carbohydrate quality and human health: a series of systematic reviews and meta-analyses.. Reynolds A et al.. Lancet 2019 · PMID 30638909 · DOI 10.1016/S0140-6736(18)31809-9
- Neutral detergent fiber, hemicellulose and cellulose digestibility in human subjects.. Slavin JL et al.. J Nutr 1981 · PMID 6257867 · DOI 10.1093/jn/111.2.287
- Effect of fiber from fruits and vegetables on metabolic responses of human subjects: fiber intakes, fecal excretions, and apparent digestibilities.. Kelsay JL et al.. Am J Clin Nutr 1981 · PMID 6269418 · DOI 10.1093/ajcn/34.9.1849
- The cellulose-degrading microbial community of the human gut varies according to the presence or absence of methanogens.. Chassard C et al.. FEMS Microbiol Ecol 2010 · PMID 20662929 · DOI 10.1111/j.1574-6941.2010.00941.x
- Cryptic diversity of cellulose-degrading gut bacteria in industrialized humans.. Moraïs S et al.. Science 2024 · PMID 38484069 · DOI 10.1126/science.adj9223