Isoflavone-free soy protein prepared by column chromatography reduces plasma cholesterol in rats

To know whether isoflavones are responsible for the hypocholesterolemic effect of soy protein, the effect on plasma cholesterol of isoflavone-free soy protein prepared by column chromatography was examined in rats Five week-old male Sprague-Dawley rats were fed cholesterol-enriched AlN 93G diets containing either 20% casein (CAS), 20% soy protein isolate (SPI) 20% isoflavone-free SPI (IF SPI), 19 7% IF-SPI + 0 3% isoflavone rich fraction (isoflavone concentrate, IC), or 20% CAS + 0 3% IC for 2 weeks Plasma total cholesterol concentrations of rats fed SPI and IF-SPI were comparable and were significantly lower than that of rats fed CAS The addition of IC to the CAS and IF SPI did not influence plasma cholesterol level Fecal steroid excretion of the three SPI groups was higher than that of the two CAS groups, whereas the addition of IC showed no effect Thus, a significant fraction of the cholesterol lowering effect of SPI in rats can be attributed to the protein content but the isoflavones and other minor constituents may also play a role.