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Inulin

A prebiotic fiber in chicory root, Jerusalem artichokes, garlic, onions and leeks.

Updated

What it is

Inulin is a chain of fructose sugars that some plants store for energy. You can’t digest it, so it reaches your colon, where bacteria ferment it. Shorter chains are called oligofructose or FOS.

Foods with the most inulin

Grams of inulin per 100 g of fresh food
FoodInulin per 100 g
Chicory root15–20 g
Jerusalem artichoke14–19 g
Garlic9–16 g
Leeks3–10 g
Onion2–6 g
Banana0.3–0.7 g

Fresh weight. Amounts vary a lot between plants.

Asparagus and wheat have some too. Because people eat so much wheat, it supplies about 70% of the inulin Americans eat, and onions about 25%.

Why fiber numbers miss it

The standard lab tests for fiber miss much of the inulin in food, so food tables, USDA’s included, often undercount it. USDA lists Jerusalem artichokes at 1.6 g of fiber per 100 g, far below their inulin content, so the fiber numbers here run low for inulin-rich foods.

What it does

  • Feeds gut bacteria. Inulin is one of the established prebiotics.
  • Can help you go more often. The EU accepts that 12 g a day of chicory inulin supports normal bowel function by increasing stool frequency.
  • Can cause gas and bloating. In one study of healthy young adults, up to 10 g a day of inulin and 5 g of oligofructose were well tolerated.

Inulin on labels

It’s added to packaged foods as “inulin” or “chicory root fiber”. The FDA lets food makers count it as fiber on the Nutrition Facts label while it plans to add it to the official definition.

Inulin is a fructan, one of the FODMAPs. If you have IBS, it may bring on gas, bloating or pain.

Questions

Which foods are highest in inulin?

Chicory root and Jerusalem artichokes, at about 14 to 20 g per 100 g, then garlic. Leeks and onions have less, and bananas only a little.

Is inulin a prebiotic?

Yes. ISAPP, the scientists’ group that wrote the definition of prebiotics, lists inulin as one.

How much inulin is too much?

It depends on the person. In one study of healthy young adults, up to 10 g a day of inulin was well tolerated, but only 5 g of oligofructose, its shorter form. Gas and bloating were the most common complaints.

Is inulin bad for IBS?

It can be. Inulin is a fructan, one of the FODMAPs, which often bring on IBS symptoms like gas, bloating and pain.

Sources

  1. Van Loo et al. (1995): On the presence of inulin and oligofructose as natural ingredients in the western diet. Critical Reviews in Food Science and Nutrition
  2. Ghali et al. (2024): Inulin-based formulations as an emerging therapeutic strategy for cancer (Table 1: rich sources of inulin). International Journal of Biological Macromolecules
  3. Moshfegh et al. (1999): Presence of inulin and oligofructose in the diets of Americans. Journal of Nutrition
  4. Bonnema et al. (2010): Gastrointestinal tolerance of chicory inulin products. Journal of the American Dietetic Association
  5. EFSA (2015): Native chicory inulin and maintenance of normal defecation by increasing stool frequency. EFSA Journal 13(1):3951
  6. A study on the analytical methods for total dietary fiber in fructan-containing foods. Journal of Food and Drug Analysis 15(3)
  7. FDA: Questions and answers on dietary fiber
  8. ISAPP: Probiotics, prebiotics, synbiotics, postbiotics and fermented foods (definitions)
  9. Monash University: 20 years of FODMAP

General information, not medical advice. If you have a health condition or take medicines, ask your doctor before adding a fiber supplement.