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Inulin & FOS (chicory)

The classic prebiotic — feeds your good bacteria, at the cost of some gas if you overdo it.

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

SupplementsFiberPrebioticGut

Inulin and its shorter cousin FOS (fructo-oligosaccharides) come mainly from chicory root. They pass to the colon undigested and are fermented — the definition of a prebiotic.

Key takeaways

  • A well-established prebiotic — selectively feeds bifidobacteria.
  • EFSA-approved: native chicory inulin improves bowel function (stool frequency) at 12 g/day.1
  • Highly fermentable — gas and bloating are common, and it’s high-FODMAP (often a trigger in IBS).
  • Start low and build up slowly to let the microbiome adapt.

What it is

Chains of fructose (long = inulin, short = FOS/oligofructose) that human enzymes can’t break down, so gut bacteria ferment them into short-chain fatty acids.

The evidence

Inulin reliably increases bifidobacteria and has an EFSA claim for normal defecation at 12 g/day.1 Broader metabolic benefits are plausible but less consistent.

Dose

Start at 3–5 g/day and build gradually to ~10–15 g/day. Rushing the dose is the usual cause of bloating.

Safety

Safe but gassy — it’s a high-FODMAP fibre and can flare IBS. If you’re sensitive, a gentler fibre (PHGG, acacia) may suit better.

Bottom line: the textbook prebiotic — great for feeding good bacteria, but go slow: it’s the gassiest of the common fibres and rough on IBS guts.

References

Adult research summary for education, not a prescription.

  1. EFSA NDA Panel: scientific opinion on native chicory inulin and maintenance of normal defecation by increasing stool frequency. EFSA Journal 2015. www.efsa.europa.eu

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.