ABSTRACT
This chapter describes the bacterial metabolism of dietary fiber and defines dietary fiber. It considers the evidence that dietary fiber is metabolized during colonic transit and this evidence is from in vivo and in vitro studies. The chapter describes the enzymes involved in fiber metabolism and discusses the consequences to the host of fiber metabolism. Fermentation of dietary fiber in the colon is of major importance both to the gut bacterial flora and to the host. The major products of fiber metabolism are the short-chain fatty acids (SCFA’s), gases and energy. Dietary fiber is equivalent to that fraction of the diet that used to be referred to as unavailable carbohydrate, and both terms have major shortcomings. The evidence that dietary fiber is degraded by the gut bacterial flora is very strong and copious, although there have been relatively few investigations of how the degradation takes place.
