Wheat bran equivalents for faecal bulking (WBEfb) are defined as the gram quantity of wheat bran that would augment faecal bulk to the same extent as a given quantity of a specified food, and its development as a food datum for the dietary management of distal colonic bulk is discussed in this paper. The WBEfb content of a food is derived from the faecal bulking index (FBI), which is a standardised physiological measure of the relative faecal bulking efficacy of foods on an equal edible weight basis. The FBI is defined as the increment in hydrated faecal matter per gram of a food consumed as a percentage of the increment due to the same weight of reference food (1 mm hard red wheat bran; FBI = 100). The FBI values allow the contribution of hydrated solids to the distal colon to be related to that of any reference of known FBI such as wheat bran, the suitability of which as a reference material is discussed. By expressing the increment in bulk as WBEfb, the relative impact of any quantity of an individual food on faecal bulk may be determined, and the effect of foods in mixed diets approximated by summation. Examples are given of the dietary management of distal colonic bulk using WBEfb, with one cup of wheat bran containing 27.5 g of dietary fibre - about the mean recommended daily fibre intake for adults--used as theoretical adequate daily intake of potential faecal bulk. The FBI and WBEfb are proposed as examples of the types of evidence-based data sets that may complement food composition data in selecting foods for physiological function.