Condition
    Moderate Evidence
    Effectiveness 3/5

    L-Glutamine for IBS (Irritable Bowel Syndrome)

    One promising trial in post-infectious IBS with increased intestinal permeability has not yet been replicated.

    Overview

    One promising trial in post-infectious IBS with increased intestinal permeability has not yet been replicated.

    Verdict

    Insufficient evidence

    How It Works

    Glutamine is the primary fuel for enterocytes and supports tight junction protein expression, which may reduce intestinal permeability.

    Dosing & Protocol

    Typical dose

    Recommended dose
    5-15g daily, divided doses
    Expected timeframe
    8 weeks in the one supportive trial; no meaningful change should be expected sooner.

    Protocol

    form
    L-glutamine powder dissolved in water, taken between meals
    duration
    8 weeks, matching the trial; stop if stool frequency and pain are unchanged
    co factor
    Interventions with stronger IBS evidence come first: a dietitian-led low-FODMAP trial, soluble fibre, peppermint oil and gut-directed CBT or hypnotherapy
    titration
    No titration; the trial used a fixed dose. Evidence outside post-infectious diarrhoea-predominant IBS is insufficient
    starting dose
    Studied dose was 5 g three times daily (15 g total) in post-infectious IBS with diarrhoea — a narrow group, not IBS generally

    Evidence

    What the studies say

    A randomised trial of 5 g three times daily in post-infectious IBS with leaky gut reported substantial symptom reduction versus placebo. The result is from a single centre in a highly selected subgroup and requires confirmation.

    Randomised clinical trial: oral glutamine reduces intestinal permeability and IBS symptoms in postinfectious IBS with diarrhoea

    Score: 8/10
    2019
    rct
    n=106

    Zhou Q, Verne ML, Fields JZ +4 more

    Oral dietary glutamine supplements dramatically reduced all major IBS-related endpoints in patients with IBS-D and increased intestinal permeability.

    View source

    Safety

    Caveats

    Evidence is insufficient: benefit rests essentially on one trial restricted to post-infectious diarrhoea-predominant IBS with raised intestinal permeability. Avoid in cirrhosis or hepatic encephalopathy, and in significant kidney impairment, since glutamine raises ammonia load. Not advised in pregnancy for lack of data.

    Less likely to help if

    Constipation-predominant IBS, IBS without a preceding gastroenteritis, and anyone whose symptoms actually reflect coeliac disease, bile acid diarrhoea or inflammatory bowel disease — all of which need excluding first.

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