- Design
- Double-blind, three-arm randomised controlled trial
- Population
- 84 adults with irritable bowel syndrome
- Primary outcome
- Oxidative stress markers and sleep quality at 90 days
- Effect
- Lower total oxidant status and oxidative stress index with zinc; no change in sleep quality
In this double-blind randomised trial, 84 adults with irritable bowel syndrome received zinc gluconate (20 mg elemental zinc) with a placebo capsule, zinc with a probiotic, or two placebos for 90 days.
Both zinc groups had higher serum zinc and lower total oxidant status and oxidative stress index than placebo. Malondialdehyde, total antioxidant capacity, superoxide dismutase activity and sleep quality did not differ between groups. IBS symptoms were not reported as an outcome in the abstract.
Changes in laboratory oxidative stress markers are surrogate outcomes. Without an effect on symptoms or sleep, the trial gives no reason to recommend zinc or this combination for IBS.
- Do not recommend zinc for IBS on the basis of this trial.
- Sleep quality did not improve with zinc or zinc plus probiotic.
- Use treatments with symptom evidence — dietary measures, soluble fibre, antispasmodics and gut-brain therapies.
- Ask about sleep in IBS; poor sleep often travels with symptom severity.
Why it matters
Supplements are often recommended for IBS on the strength of biomarker changes that patients cannot feel.
Don't overread it
Oxidative stress markers are surrogates; they do not show the patients felt better.
The statistics, in plain English
A significant change in a laboratory marker means the supplement did something measurable, not that it helped. Only outcomes patients experience — pain, bowel habit, sleep — show benefit.
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