Dietary psyllium hydrocolloid and pectin increase bile acid pool size and 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 hydrocolloid/100 g diet using the washout technique. Bile acid pool sizes were similar for pectin- and psyllium-fed rats, and both were higher than the pool size for rats fed cellulose (5.48 +/- 1.22, 4.70 +/- 0.71 and 1.77 +/- 0.41 mumol/100 g body wt, respectively). Bile acid secretion rates showed a similar pattern [1730 +/- 496, 1551 +/- 252 and 572 +/- 88 nmol/(h.100 g body wt)], as did basal synthetic rates [129 +/- 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 the pectin- or psyllium-supplemented diet compared with rats fed cellulose. Pectin or psyllium consumption resulted in a lower hydrophobicity of the bile acid pool and a lower ratio of circulating 12 alpha-hydroxylated to non-12 alpha-hydroxylated bile acids compared with cellulose consumption. This reduced hydrophobicity has been shown to reduce feedback inhibition of bile acid synthesis and may be responsible for the 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 excretion.