Cholesterol reduction by glucomannan and chitosan is mediated by changes in cholesterol absorption and bile acid and fat excretion in rats

Glucomannan, a Viscous polysaccharide, and chitosan, a derivative of chitin , have both been demonstrated to lower cholesterol in animals. However, the mechanism of cholesterol lowering has not been established for either mate rial. This study was conducted to determine the effect of glucomannan (G), chitosan (CH), or an equal mixture of the two (G + CH) on cholesterol absor ption and fat and bile acid excretion. Rats were fed a modified AIN-93G die t for 18 d containing 0.125 g/100 g cholesterol and initially 10 g/100 g of the test materials or cellulose (G) as the control. However, the concentra tion of test materials and cellulose was reduced to 7.5 g/100 g after 1 wk due to lower weight gain compared with controls. Total liver cholesterol wa s significantly reduced in G, CH and G + CH groups compared with the C grou p. The intestinal contents supernatant viscosity of the C and the GH groups was negligible, whereas both G and G + CH produced high viscosities. Chole sterol absorption, measured by the fecal isotope ratio method, was signific antly reduced from 37.5% in the C group to 20.2% in G, 18.2% in G + CH and 9.4% in CH. Daily fecal fat excretion did not differ between the C and G gr oups, but was significantly greater in G + CH and CH compared with the C an d G groups. Daily fecal bile acid excretion was significantly greater in th e CH and G + CH groups compared with the C and G groups. These results sugg est that G lowered liver cholesterol by a viscosity-mediated interference o f cholesterol absorption. In contrast, CH appears to lower cholesterol thro ugh a different mechanism.