Comparison of the effects of condensed tannin and pectin on cecal fermentations and lipid metabolism in the rat

Abstract

The aim of the study was to compare the effect of a soluble fiber (citrus pectin) and prefermented condensed tannin (Quebracho) on the cecal fermentations, bile acids excretion and lipid metabolism in rats fed semi-purified diets. Analysis of the fermented tannin established than it is rich in monomers and trimers with little highly condensed polymers. Food intake and weight gain were not affected by addition of 5% citrus pectin or 1% Quebracho tannin in the diet. In the cecum, there was evidence of a depolymerization of polymers and of degradation of monomers, together with an accumulation of polar phenolic compounds. There was a significant enlargement of the cecum and of the volatile fatty acids (VFA) pool in rat fed the pectin diet; the Quebracho diet depressed the cecal VFA concentrations, compared to controls. The 1% Quebracho diet enhanced bile acids excretion, but the 5% pectin diet did not. In contrast, plasma cholesterol was depressed more effectively by pectin than by Quebracho. Both diets increased the activity of liver HMG-CoA reductase, a rate limiting enzyme of cholesterogenesis. The data show that, at a relatively low level in the diet, condensed tannins and soluble fibers may affect lipid metabolism by distinct mechanisms, which could be complementary in natural product diets.