Bran

Bran is the outer hard layer of a cereal grain, made up of the aleurone and pericarp surrounding the endosperm, and is removed as a byproduct when grains are milled into refined products such as white flour and white rice. It is dense in dietary fiber, essential fatty acids, starch, protein, vitamins and minerals, though it also carries phytic acid, an antinutrient that inhibits nutrient absorption, and its high oil content makes it prone to turning rancid in storage. Bran is commonly used to enrich breads, especially muffins, and breakfast cereals for people seeking more fiber, and rice bran in particular is used in Japanese pickling as nuka; it also serves as livestock feed and can be pressed into baking oil. Because it is difficult to digest on account of its high fiber content, bran is typically removed during the refining that produces white flour and white rice.