Microbiome Interpretation Structured microbiome reference
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Fiber supplements compared

Isolated fibers differ in viscosity, fermentability, and clinical trial evidence. Psyllium has the strongest IBS symptom data among common supplements; inulin and FOS are potent prebiotics but overlap high-FODMAP effects.

Fiber supplements compared

Extends The dietary fiber paradox. This page compares common isolated products, not an exhaustive catalog.

SupplementTypeIBS symptom RCTs (summary)Microbiome (typical)Caution
Psyllium (ispaghula)Soluble, gel-forming, moderate fermentationBenefit in meta-analysesModest shiftsTake with water; gradual dose
Wheat branInsolubleNo clear benefit; dropout/worsening in some trialsBulkingCan worsen bloating
Inulin / FOSHighly fermentable prebioticMixed; gas common↑ Bifidobacterium oftenHigh FODMAP
GOSFermentable prebioticIBS variable↑ bifidobacteriaFODMAP overlap
PHGG (partially hydrolyzed guar gum)Soluble, low viscositySome IBS benefit in trials↑ Bifidobacterium, Faecalibacterium in studiesGenerally better tolerated than inulin in some cohorts
MethylcelluloseNon-fermentable solubleConstipation relief (laxative data)Minimal fermentationLess prebiotic effect
Resistant starchFermentableMetabolic/butyrate research↑ butyrate producers (variable)See /interventions/resistant-starch

ACG / primary care: psyllium among best-supported fibers for global IBS symptoms in guidelines citing Moayyedi meta-analysis.

Context if you're reading a report

Reports recommending "more fiber" without type send sensitive readers toward wheat bran or inulin, with opposite outcomes in trials.

Expect genus shifts (e.g. Bifidobacterium on inulin) that may not match symptom tolerance or clinical endpoints.

That all fiber supplements are equivalent; that fermentable prebiotics are always appropriate for IBS; or that supplements replace diverse whole-food fiber.