Bran is often confused with dietary fibre. Although it contains fibre, the term actually refers to the outer husk of seeds and grains. It has been shown to accelerate oro-caecal transit (OCT) with scintigraphy. Bran can also be shown to increase small bowel water content, possibly by mechanical stimulation, one of the most powerful stimuli for small intestinal secretion, which may be a mechanism to prevent blockage. In the past bran's high fibre content led to the hypothesis that its effect derived from holding water in the lumen but a comparison study of 17 different fibres found an inverse relationship between their water-holding properties and effect on faecal weight, with bran holding the least water but inducing the largest weight changes. Rather, weight change appeared to relate to the amount of undigested fibre present in the faeces and the associated changes in bacterial numbers, which account for most of dry stool weight.