Fructans (inulin, FOS)

Fermentable fibers

Chains of fructose that the small intestine does not touch: they reach the colon whole.

They are also the FODMAPs of onion and wheat: increase gradually if the gut is sensitive.

Effects and benefits

The fiber of onion, garlic, leek and chicory, the one that most reliably grows bifidobacteria. At 12 g a day, chicory inulin makes transit more regular; in adolescents, it even helped bones take up more calcium.

Fructans are chains of fructose that our enzymes cannot cut. They cross the small intestine intact and become, in the colon, the favorite meal of bifidobacteria, which ferment them into lactic and acetic acids; other bacteria then turn these acids into butyrate. It is a relay.

Chicory inulin contributes to the maintenance of normal bowel function by increasing stool frequency, from 12 g a day (Regulation 2015/2314).

A one-year trial in adolescents gave an unexpected result: 8 g a day of a mix of inulin and FOS increased calcium absorption and bone mineralization, at the age when the skeleton is being built (Abrams et al., 2005). The acidity produced by fermentation makes calcium more soluble in the colon.

Europeans eat 3 to 10 g a day, mostly from wheat and onion (van Loo et al., 1995); a serving of Jerusalem artichoke or salsify provides more in one go than a whole ordinary day.

Bifidobacterium. It is the best-established effect in all of prebiotic nutrition, and the most reproducible from one person to the next.

Sources: EU Regulation 2015/2314 · Abrams et al., AJCN, 2005 · van Loo et al., Crit Rev Food Sci Nutr, 1995

Where to find it (33)

Also, in smaller amounts (25)

Its category: Fructans & inulin