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Methylcellulose

A bulk-forming fibre that doesn't ferment — so it eases constipation with virtually no gas.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsFiberBulk-formingNon-fermenting

Methylcellulose (the fibre in Citrucel) is made from plant cellulose. Its trick is that gut bacteria can’t ferment it — so it bulks stool without producing gas.

Key takeaways

  • A bulk-forming fibre for constipation and regularity.
  • Non-fermentable — so it causes little or no gas/bloating.
  • Because it doesn’t ferment, it has no meaningful prebiotic or cholesterol effect.
  • Take with plenty of water like any bulk fibre.

What it is

A semisynthetic soluble fibre derived from cellulose. It holds water to add soft bulk to stool but is not fermented by gut bacteria.

The evidence

An established bulk laxative for constipation. Its selling point is comfort — the lack of fermentation means minimal gas.1 Don’t expect the cholesterol or microbiome benefits of viscous/fermentable fibres.

Dose

Per product label (typically ~2 g per dose, up to a few times daily) with a full glass of water each time.

Safety

Very safe; take with adequate water to avoid obstruction. Separate from medicines.

Bottom line: a comfortable, gas-free bulk fibre for regularity — ideal if fermentable fibres bloat you, but it won’t touch cholesterol or the microbiome.

References

Adult research summary for education, not a prescription.

  1. McRorie JW, Chey WD. Fermented fiber supplements are no better than placebo for a laxative effect. Dig Dis Sci, 2016;61(11):3140–6. pubmed.ncbi.nlm.nih.gov

This article summarises nutrition science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.