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Prebiotic fiber

Prebiotics

inulin, FOS, GOS

Fibers that feed beneficial gut bacteria, such as inulin and fructooligosaccharides.

Evidence: Moderate

Evidence by use: Moderate for increasing beneficial bifidobacteria; limited for clinical outcomes. Reviews of inulin-type fructans report increases in bifidobacteria and effects on stool, but clinical benefits are less certain and responses vary between people.

At a glance

Typical studied dose
Studies commonly use about 3-10 g per day of inulin-type fructans. Start low and increase slowly.

Food sources

Animal sources
Small amounts in breast milk (oligosaccharides).
Plant sources
Chicory root, Jerusalem artichoke, garlic, onions, leeks, asparagus, bananas, oats, legumes.

Background and testing

This is not an essential nutrient, so there is no deficiency to diagnose.

Who tends to use it
People with low fiber intake.
How it is tested
No lab test.

Supplement forms

Common forms
Inulin or FOS powders, GOS powders, partially hydrolyzed guar gum, resistant starch, prebiotic gummies and sodas.
More effective
Whole foods first; for supplements, a gradual increase from a small dose, taken with plenty of fluids.
Less effective
Large starting doses (gas, bloating, cramps); prebiotic sodas or gummies with a tiny fiber dose; use during a low-FODMAP elimination phase.

Safety, interactions and halal notes

Safety and interactions
Common side effects at higher doses are gas, bloating and loose stools. People with IBS or SIBO may react poorly.
Who should avoid it or ask a clinician first
People with IBS or SIBO should ask a clinician; people on a low-FODMAP diet.
Halal note
Plant-derived. Check any gelatin-based gummy or capsule shell.

Frequently asked questions

Prebiotic vs probiotic?

Probiotics are live microbes. Prebiotics are fibers that feed microbes already in your gut.

Sources

  1. The Prebiotic Potential of Inulin-Type Fructans: A Systematic Review (Adv Nutr, 2022)

← Back to the full nutrient guide

This page is for education only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a qualified clinician before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a medical condition. Daily needs are US reference intakes for adults 19-50.

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