Here is some information about bran:
“Along with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in the production of refined grains. When bran is removed from grains, the grains lose a portion of their nutritional value. Bran is present in and may be milled from any cereal grain, including rice, corn (maize), wheat, oats, barley and millet. Bran should not be confused with chaff, which is coarser scaly material surrounding the grain, but not forming part of the grain itself.
Bran is particularly rich in dietary fiber and essential fatty acids and contains significant quantities of starch, protein, vitamins, dietary minerals and phytic acid, which is an antinutrient that prevents nutrient absorption.”