Effect of Dietary Wheat Bran, Alfalfa, Pectin and Carrageenan on Plasma Cholesterol and Fecal Bile Acid and Neutral Sterol Excretion in Rats

Abstract

The effect of dietary wheat bran, alfalfa, pectin and undegraded carrageenan at a level of 15% on the composition of fecal bile acids and neutral sterols and on the plasma and liver cholesterol levels was studied in Fischer female rats fed a semi-purified diet based on soybean protein, cornstarch, dextrose and corn oil. The diets differed not only in type of fiber but also in amount of fiber. Plasma cholesterol levels were reduced in rats fed pectin or carrageenan diet but were not altered by the addition of wheat bran or alfalfa to the diet. Liver cholesterol levels were comparable in all groups. Diets containing wheat bran, alfalfa and carrageenan caused a significant increase in feces weight. The concentration (mg/g dry feces) of fecal bile acids, particularly hyodeoxycholic acid, β-muricholic acid, deoxycholic acid and lithocholic acid, and of neutral sterols, mainly coprostanol, was lower in rats fed wheat bran compared to those fed a control diet, but the daily output of these constituents was the same in both groups. Alfalfa had no effect on the concentration of fecal bile acids, but the daily excretion of deoxycholic acid, lithocholic acid and 12-ketolithocholic acid was increased compared to the control diet. Addition of pectin to the diet increased the concentration and daily output of fecal neutral sterols and bile acids compared to that of control diet. Carrageenan markedly increased the concentration and daily output of fecal cholesterol, deoxycholic acid and lithocholic acid, as well as the daily output of total bile acids. It is concluded that the plasma cholesterol-lowering effect and fecal bile acid and neutral sterol excretion vary with type and amount of fiber.