Effects of Dietary Roughage on Cholesterol Absorption, Cholesterol Turnover and Steroid Excretion in the Rat

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Abstract
We have observed that commercial rat diet and its grain components desolubilize both cholesterol and sodium taurocholate from a micellar solution. We have also studied cholesterol absorption, plasma cholesterol concentration and turnover, and excretion of fecal steroids in rats fed either a commercial stock diet or a low or high residue semisynthetic diet. The percentage of an oral dose of radioactive cholesterol absorbed was shown to be approximately 60% in rats fed either the stock diet or the semisynthetic diet by two independent isotope ratio methods. Plasma cholesterol concentration was significantly lower in rats fed stock diet, while removal of radioactive cholesterol from plasma and excretion of radioactive steroids in feces were greater in rats fed stock diet than in those fed the low residue semisynthetic diet. Plasma cholesterol concentrations were lower and steroid excretion was increased in rats fed the semisynthetic diet plus a relatively nondigestible soybran supplement as compared to those receiving unsupplemented semisynthetic diet. Our data suggest that nondigestible components of the stock diet have a major influence on plasma cholesterol concentration and turnover and on fecal excretion of steroids, but that they do not inhibit absorption of dietary cholesterol.