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Moderate evidenceGut health

Prebiotic fibre

Also called: Inulin, FOS, GOS, PHGG

Fibres that feed your good gut bacteria. Start with a small amount to avoid gas.

Typical amount
Start at 2–3 g a day, build to 5–10 g
Best time
Any time, with water or food; start small · Timing guide
Food
With or without food
Typical course
8 weeks, then review
Is it right for me?

Where to buy

3 products
Also inside 1 other product (combinations and multivitamins)

What is prebiotic fibre?

Prebiotics are fibres you can't digest but your gut bacteria can. They increase beneficial bacteria like bifidobacteria and help produce short-chain fatty acids that nourish the gut lining. Inulin and FOS come from chicory and other plants.

Forms. Powders and sachets; often added to probiotics and fibre drinks.

What it may help with

Evidence grade

Strong: several good human trials. Moderate: some trials, mixed results. Limited: small or early studies. Traditional: long use, little trial evidence.

Safety and interactions

Side effects
Gas and bloating, especially at first. People with IBS should start very low.
Who should be careful
Can cause gas at first; IBS: start very low
Spacing
2 h apart from medicines
Stop and call a doctor if
Severe bloating or pain

Food sources

Onion, garlic, leeks, bananas (slightly green), oats, barley, and cooked-and-cooled rice or potato.

Common questions

How much should I take?

Start with 2–3 g a day and build up to 5–10 g over a few weeks.

Prebiotic or probiotic?

Prebiotics feed your own bacteria; probiotics add new ones. They can be used together.

Do I need a supplement?

Not if you eat plenty of onions, garlic, oats and pulses.

For information only, not medical advice. Prices and links are checked by hand and can change; we may earn a small commission on some links. This plan is based on your answers and is not a medical diagnosis. It does not replace advice from your doctor. If you take medicines or have a health condition, check with your doctor before starting any supplement.