This study investigates the mechanisms of action for the hypocholesterolaemic effects of sugar-beet fibre (SBF) and gum gum. Four groups of ten male Wistar rats were fed ad lib. on test diets containing either 100 g SBF or guar/kg, or control diets containing 100 g cellulose or wheat bran/kg for 28 d. Food intake, weight gain and food consumption ratios were unaffected by the diets. Circulating cholesterol and hepatic cholesterol concentrations were significantly lower in both SBF- and guar-fed groups compared with either cellulose- or bran-fed animals. Circulating triacylglycerol concentrations were significantly lower in SBF- and guar-fed animals, but total hepatic lipid concentrations and hepatic and adipose tissue lipogenesis rates were unaffected by the diets. Hepatic cholesterol-7α-hydroxylase (EC1.14.13.17) activities were significantly higher in the guar-fed animals compared with cellulose or bran control groups. Hepatic 3-hydroxy-3-metbylglutaryl-CoA reductase (EC1.1.1.88) activities were unaffected. Circulating bile acid concentrations were significantly lower in SBF- and guar-fed animals and faecal bile acid output was significantly higher in the guar-fed group compared with bran- or cellulose-fed groups. This study supports the hypothesis that guar exerts its hypocholesterolaemic effect via intraluminal bile acid binding and loss of cholesterol from increased faecal bile acid excretion. The mechanism of action for the hypocholesterolaemic effect of SBF is less clear; the results of the present study point to a mechanism involving disruption of the enterohepatic bile acid circulation, possibly via changes in the rate of absorption of dietary lipid.

A sugar-beet fibre preparation (SBF) was incorporated into a semi-synthetic rat diet at a level of 100 g/kg. The material caused no feed aversion, and gain of live weight was unimpaired. SBF appeared to be slightly more fermentable than wheat bran and only marginally less effective as a faecal bulking agent when compared with equalized intakes of non-starch polysaccharide. SBF did not stimulate mucosal cell turnover in the small intestine. Some enlargement of the caecum was observed in animals given SBF, but it was no greater than that of animals given wheat bran. Animals given SBF had a lower serum cholesterol concentration than both the fibre-free controls and those given wheat bran. This hypocholesterolaemic effect was less than that of guar gum however. The partial digestibility of energy for SBF was 0.64, and its partial digestible energy value was 11.3 kJ (2.7 keal)/g. The partial digestibility of energy for non-starch polysaccharide in SBF was estimated to be 0.53 and its partial digestible energy value was 9.1 kJ (2.2 kcal)/g. This value was not significantly different from that expected for unavailable carbohydrate in mixed human diets.