Specific effect of guar gum or gum arabic on adaptation of cecal digestion to high fiber diets in the rat.

The objective of this work was to examine whether the nature of fiber may influence the cecal digestion in the rat fed hydrocolloids such as gums. Adaptation to a high fiber diet containing 15% guar gum (GG) or gum arabic (GA) was thus studied in rats previously adapted to a high starch fiber-free diet. Both gums elicited a marked enlargement of the cecum and a trophic effect on the cecal wall. The cecal pH dropped to 5.8, then plateaued to about 6.1. During the first days of adaptation, a part of GA escaped microbial degradation; thereafter the cecal pool of volatile fatty acids (VFA) was similar with both diets (approximately equal to 1000 mumol). GA promoted propionate-rich fermentations, whereas GG rather enhanced acetic and butyric fermentations. VFA absorption was higher with the gum diets than with the control diet, because blood flow increased in parallel to the weight of cecal wall. K+, Mg2+ and Ca2+ were absorbed in large amounts from the cecum, particularly in rats fed the GA diet. With this diet, high concentrations of nonsoluble Ca2+ and phosphate (but low concentrations of soluble phosphate) were found in the cecum. The study indicates that gums have potent effects on digestion in the large bowel, and that there are specific effects of the different types of gums.