Some physical characteristics of dietary fibres and their influence on the microbial ecology of the human colon.

Current thinking on the subject of dietary fibre tends to emphasize an inclusive definition that overlooks disparate characteristics of individual fibres and their components. The current definition includes all carbohydrate and some noncarbohydrate components that are resistant to mammalian enzymes. The analytical approach proposes to resolve the differences between sources of fibre by characterizing the different proportions of cellulose, hemicellulose, pectin, etc. and in turn resolving these into their respective component sugars. Forage analysis, largely applied to nutrition of ruminants, has emphasized the nutritional non-uniformity of cellulose and hemicellulose despite similarities in chemical linkage and structure of the respective components among different species of forage plants. This has led to the suggestion that intrinsic differences among celluloses are due to macromolecular interactions rather than to their intrinsic structure and composition (Van Soest, I 982). This paper applies the same view to dietary fibre in human nutrition and provides some evidence that physical properties are major determinants of the biological properties of dietary fibre in the human digestive tract.