15% of the wheat berry is wheat bran and 3 % is wheat germ.
Wheat endosperm contains only minor amounts of substances which could be called fiber.
Wheat bran represent a rich source of water-insoluble fiber that is mainly cellulose. Insoluble fiber is implicated in maintaining the health of the gastrointestinal tract in several ways.
In general, water insoluble fibers are less subject to fermentation and hold more water than do the water soluble fibers.
Therefore , water insoluble fibers have a greater effect on stool mass than water-soluble fibers. Wheat bran adds bulk and relieves constipation because it absorbs water, making the stool soft.
Wheat is nutritionally the richest part of the wheat berry and contains higher proportion of soluble fiber than bran, as might be imagined for a plant embryo.
Fiber in wheat