Oat hull fiber is an insoluble source of dietary fiber, derived from t
he outermost layer of the oat grain. The effect of oat hull fiber on c
olonic function and serum lipids was investigated by conducting a cont
rolled study on IO healthy males, aged 20-37, who ate, for two three-w
eek periods, a controlled low fiber diet (13.1 g of nonstarch polysacc
haride [NSP]/day), and the same diet with 25 g of oat hull fiber per d
ay incorporated into foods, providing 17 g of NSP/day. Fecal weight in
creased from 113 +/- 10.4 to 155 +/- 10.8 g/day (P < 0.001) with no ch
ange in transit time or serum lipids. Fermentation of oat hull fiber w
as studied by analysis of feces for NSP. Excretion of NSP increased fr
om 2.0 g/day excreted to 19.7 g/day, indicating that no degradation ha
d occurred. Oat hull fiber is therefore resistant to fermentation in t
he human colon, has no effect on serum lipids, and provides no energy
to the body.