DIETARY PSYLLIUM HYDROCOLLOID AND PECTIN INCREASE BILE-ACID POOL SIZEAND CHANGE BILE-ACID COMPOSITION IN RATS

Bile acid composition, synthetic rate and pool size were determined in rats fed diets containing 5 g cellulose, 5 g pectin or 5 g psyllium h ydrocolloid/100 g diet using the washout technique. Bile acid pool siz es were similar for pectin- and psyllium-fed rats, and both were highe r than the pool size for rats fed cellulose (5.48 +/- 1.22, 4.70 +/- 0 .71 and 1.77 +/- 0.41 mu mol/100 g body wt, respectively). Bile acid s ecretion rates showed a similar pattern [1730 +/- 496, 1551 +/- 252 an d 572 +/- 88 nmol/(h.100 g body wt)], as did basal synthetic rates [12 9 +/- 25, 126 +/- 42 and 87 +/- 18 pmol/(h.100 g body wt)]. Individual and total bile acid pool sizes were generally higher in animals fed t he pectin- or psyllium-supplemented diet compared with rats fed cellul ose. Pectin or psyllium consumption resulted in a lower hydrophobicity of the bile acid pool and a lower ratio of circulating 12 alpha-hydro xylated to non-12 alpha-hydroxylated bile acids compared with cellulos e consumption. This reduced hydrophobicity has been shown to reduce fe edback inhibition of bile acid synthesis and may be responsible for th e larger bile acid pool size. Changes in the location of reabsorption of bile acids may also be responsible for changes in the pool size and composition. These changes are characteristic of greater sterol excre tion.