The Journal of Nutrition Vol. 127 No. 3 March 1997, pp. 463-469
Copyright ©1997 by the American Society for Nutritional Sciences

Native and Partially Hydrolyzed Psyllium Have Comparable Effects on Cholesterol Metabolism in Rats

Manuscript received 22 August 1996. Initial reviews completed 26 September 1996. Revision accepted 31 October 1996.

University of Illinois at Chicago, Chicago, IL 60612 and ^* The Procter & Gamble Company, Mason, OH 45040

This study was conducted to determine whether the storage conditions and the levels of psyllium in the diet modulate its hypocholesterolemic effects. Seventy-five male Sprague-Dawley rats, age 90 d, were randomly divided into five treatment groups and were fed cholesterol-containing diets for 21 d. Diets included 10% cellulose (control); 5 or 10% psyllium stored 8 mo at 5°C (PS₅); or 5 or 10% psyllium stored 8 mo at 40°C (PS₄₀). The higher storage temperature caused a gradual decrease in molecular weight of the psyllium, as measured by changes in solution viscosity. Hepatic rates of sterol synthesis were significantly (P < 0.001) higher in all of the psyllium-fed rats compared with control rats [21 ± 2, 312 ± 35, 464 ± 40, 328 ± 49 and 439 ± 57 nmol [³H]digitonin-precipitable sterol (DPS)/(g liver·h), respectively, for control, 5% PS₅, 10% PS₅, 5% PS₄₀ and 10% PS₄₀]. A similar trend was observed in intestinal rates of sterol synthesis, and the difference was significant (P < 0.05) for all treatment groups except the 5% PS₅-fed group compared with the control group. Liver total cholesterol and total lipid concentrations were significantly lower in all psyllium-fed rats compared with controls. There were no significant differences in serum total cholesterol concentrations among the psyllium-fed groups, although serum cholesterol levels in both the PS₅-fed groups were significantly (P < 0.05) lower than that in the control group (2.66 ± 0.18, 2.62 ± 0.15 and 3.26 ± 0.12 mmol/L, respectively, for 5% PS₅, 10% PS₅ and control). Serum triglyceride and HDL cholesterol concentrations did not vary significantly among groups. The findings of this study indicate that the cholesterol-lowering activity of psyllium is unaltered by storage conditions shown to cause a moderate degree of hydrolysis.

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