Abstract: Dietary fiber, obtained from extracting wheat bran with water, having an average molecular weight of 5.times.10.sup.2 to 1.times.10.sup.5, from 95.3 to 99.0% by weight of a sugar, primarily glucose, and 0.1 to 3.0% by weight protein components. The fiber, when eaten, promotes the digestion and absorption of nutrients, waste excretion and proliferation of Lactobacillus bifidus in the large intestine.