Effect of Soy Protein, Isoflavones and Methionine Supplementation on Lipid Metabolism
A series of experiments analyzed the interaction of soy protein, dietary isoflavones and methionine supplementation as possible hypocholesterolemic agents. Results from our time course experiment indicated that gerbils fed casein had higher serum total cholesterol concentrations compared to gerbils fed alcohol-washed, essentially isoflavone-free isolated soy protein (ISP). This effect was statistically significant at day-14 and continued on day-21 where the effect was more pronounced. A second study was conducted to evaluate dietary isoflavones and methionine concentrations on gerbils. Results from these studies indicated that total cholesterol levels were significantly lower (p < 0.05) in the soy-fed group, compared to casein-fed group, except in the ISP group supplemented with methionine. This study confirmed that dietary methionine concentrations might affect total cholesterol concentrations. In order to evaluate the capacity of methionine as a possible agent influencing changes in lipid parameters, a third study was conducted. This study evaluated soy protein, dietary isoflavones and graded doses of methionine. Results obtained from this study demonstrated that choline supplementation caused remarkable changes in serum lipid concentrations compared to previous studies (Tovar-Palacio et al., 1998). Serum total-cholesterol concentrations were similar in casein-fed group and soy-fed groups. However when an alcohol extract of ISP was added to soy-fed groups, a significant reduction in total cholesterol values was observed. The purpose of our last animal study was to evaluate the interaction of soy protein isoflavones and choline concentrations. Gerbils fed choline-supplemented diets showed an increase in total-cholesterol concentrations compared to animals without choline supplementation.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign