Effects of psyllium hydrophilic mucilloid on LDL-cholesterol and bile acid synthesis in hypercholesterolemic men.

The goal of the current study was to determine the mechanism of the hypocholesterolemic effect of psyllium using a randomized, double-blind, crossover design. Twenty males (age 44 * 4 yr, weight 79 * 10 kg) with moderate hyper- cholesterolemia (total 265 * 17 mg/dl, low density lipoprotein (LDL) 184 * 15 mg/dl) were studied at baseline (B) and after randomization to receive a 40-day course of 15 g/day of either psyllium (Ps) or placebo (Pl) (cellulose). After a washout period (11 f 2 days), subjects were crossed over to the other fiber treat- ment for an additional 40 days and restudied. Intestinal cholesterol absorption, cholesterol synthesis in isolated peripheral blood mononuclear cells, bile acid kinetics, gallblad- der motility, and intestinal transit were measured at each study period. Psyllium lowered LDL cholesterol (x:184 (B), 169 (Ps), and 179 (Pl) mg/dl; Ps vs. B,Pl: P < 0.004, P < 0.02), decreased relative cholesterol absorption (e51 (B), 45 (Ps), and 49 (Pl) 5%; Ps vs. B,Pl: P < 0.03, P < 0.03), did not alter absolute cholesterol absorption, and increased the fractional turnover of both chenodeoxycholic acid (20.176 (B), 0.203 (Ps), and 0.170 (Pl) day-'; Ps vs. B,Pl: P < 0.0001, P < 0.01) and cholic acid (% 0.303 (B), 0.411 (Ps), and 0.301 (Pl) d-1; Ps vs. B, P1: P < 0.006, P < 0.002). Bile acid synthesis increased in subjects whose LDL cholesterol was lowered by more than 10% (Ps vs. B: 1304 * 489 vs 992 * 307 pmollday, P < 0.006; Ps vs. PI: 1304 * 489 vs. 914 f 321 pmoyday, P < 0.0002). We conclude that psyl- lium lowers LDL cholesterol primarily via stimulation of bile acid synthesis.-Everson, G. T., B. P. Daggy, C. McKinley, and J. A. Story. Effects of psyllium hydrophilic mucilloid on LDL-cholesterol and bile acid synthesis in hypercholesterolemic men. J Lipid Res. 1992. 33: 1183-1192.