Mechanism#
Dietary fiber (cereals, fruits, vegetables, legumes) undergoes anaerobic fermentation by colonic bacteria, producing short-chain fatty acids—primarily butyrate, propionate, and acetate.
Butyrate is the preferred energy source for colonocytes and exerts direct anti-tumor effects: it inhibits histone deacetylase (HDAC) activity, induces cell cycle arrest and apoptosis in transformed cells, and suppresses pro-inflammatory NF-kB signaling.
Rationale#
Colorectal cancer develops in an environment of depleted SCFA producers, reduced butyrate availability, and compromised epithelial barrier function. Dietary fiber applies two-sided ecological engineering (Primitive 5)—it feeds beneficial SCFA-producing taxa (Faecalibacterium, Roseburia, Eubacterium rectale) while the butyrate produced directly inhibits tumor cell proliferation.
Evidence Status#
Epidemiological: Multiple meta-analyses confirm inverse association between fiber intake and CRC risk (~10% reduction per 10g/day). Mechanistic: Butyrate's HDAC inhibition and apoptosis induction in CRC cells are well-established. Animal model: High-fiber diets reduce tumor burden in APC-min mouse models.
Clinical: Validated at the epidemiological level; interventional RCTs for fiber in CRC prevention show mixed results (likely due to intervention duration).
Open Questions#
Unresolved questions identified by the current evidence record.
01Optimal fiber type (cereal vs. fruit vs. resistant starch) for maximal CRC protection.+
The current WikiBiome record identifies this as an unresolved evidence gap.
02Whether fiber intervention can reduce recurrence in CRC survivors.+
The current WikiBiome record identifies this as an unresolved evidence gap.
03Minimum duration of high-fiber diet needed for protective microbiome shifts.+
The current WikiBiome record identifies this as an unresolved evidence gap.
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