Reduced digestibility of beef tallow and cocoa butter affects bile acid excretion and reduces hepatic esterified cholesterol in rats

We investigated stearic acid (18:0) digestibility and how it affects bile acid excretion in male Sprague-Dawley rats fed diets containing (g 18:0/100 g fatty acids): pork lard (13); beef tallow (19); cocoa butter (35); corn oil (2) or corn oil plus cholestyramine for 25 d. Apparent lipid digestibility was reduced with increased dietary intake of 18:0 as follows: lard (90%), beef tallow (82%), cocoa butter (78%), cholestyramine (87%), and corn oil (94%); P < 0.001, pooled SD = 2. Hepatic concentrations of total and esterified cholesterol were significantly less in cocoa butter-, beef tallow- and cholestyramine-fed groups compared with lard- and corn oil-fed groups. Fecal bile acid excretion was significantly greater in rats fed cocoa butter or cholestyramine compared with those fed corn oil. The half-life of intraperitoneally administered ¹⁴C-cholic acid was significantly longer in rats fed cocoa butter (1.36 ± 0.02 d) compared with cholestyramine (0.98 ± 0.03 d) and intermediate in those fed corn oil, lard or beef tallow (1.11- 1.21 ± 0.05 d). Fecal excretion of muricholic acids (bile acids) correlated strongly with dietary intake of 18:0 (r² = 0.98, P < 0.01), whereas excretion of bile acids derived from cholic and chenodeoxycholic acids was similar among groups. In summary, the lower digestibility of cocoa butter is associated with increased fecal bile acid excretion, reduced hepatic concentration of esterified cholesterol, decreased fractional turnover of ¹⁴C-cholic acid and increased excretion of muricholic acids in rats. The mechanism by which stearate-rich dietary fats alter bile acid and cholesterol metabolism is, however, uncertain.