Arabinoxylans

Fermentable fibers

The main fiber of cereal bran. Fermented slowly, it travels far into the colon, where few substrates still arrive.

Rye is the richest, ahead of whole wheat and barley. Refining removes them entirely.

Effects and benefits

The fiber of bran, fermented so slowly that it feeds bacteria all the way to the far end of the colon, where almost nothing else arrives. It speeds up transit, increases stool bulk and softens blood sugar after a meal.

Arabinoxylans make up most of the walls of bran: a xylose backbone bristling with arabinose branches, sometimes attached to ferulic acid. The structure is so branched that bacteria have to team up, each cutting one type of bond: fermentation thus spreads along the whole colon, down to the left colon, where fast fibers are already used up.

Wheat bran fiber contributes to an acceleration of intestinal transit, from 10 g a day, and to an increase in fecal bulk; and arabinoxylan from wheat endosperm contributes to a reduction of the blood glucose rise after a meal, from 8 g per 100 g of carbohydrates (Regulation 432/2012).

Their small fragments, AXOS, are among the fibers that raise bifidobacteria best: in trials, a few grams a day were enough within a few weeks (François et al., 2012).

Sources: EU Regulation 432/2012 · François et al., Br J Nutr, 2012 · EFSA, 2011

Arabinoxylans

Effects and benefits

Where to find it (17)

Also, in smaller amounts (37)