Soy Isoflavones and Cholesterol Levels.




Am J Clin Nutr

Related Monographs

Consumer Data: Soy Isoflavones Hyperlipidemia
Professional Data: Soy Isoflavones Hyperlipidemia


Scientists classify soy isoflavones from the plant Glycine max as phytoestrogens. Phyto is a Greek root word meaning plant, so phytoestrogens are plant-based compounds that have estrogen-like activity. Because they are structurally similar to estrogens, isoflavones exert weak estrogenic activity. Because of their estrogen-like effects, isoflavones have been studied for a wide spectrum of health benefits.

Soybeans and soy foods like tofu are the best dietary source of isoflavones. However, many soy protein concentrates and soy products processed with alcohol may not contain isoflavones. A synthetically derived form of isoflavones, known as ipriflavone, is also available.

A recent meta-analysis published in the March issue of the American Journal of Clinical Nutrition studied the effects of soy protein and isoflavones on cholesterol levels. From 1995 to 2002, 23 studies were chosen for this meta-analysis. After reviewing these studies, researchers found that soy protein with isoflavones were associated with decreases in total serum cholesterol levels, as well as increases in HDL cholesterol (the “good” cholesterol). These reductions were seen more in men than women. In addition, studies that had intakes greater than 80 mg showed a better lipid profile in the participants. Taking isoflavones in tablet form did not show these results. The authors concluded that, “Soy protein containing isoflavones significantly reduced serum total cholesterol, LDL cholesterol, and triacylglycerol and significantly increased HDL cholesterol, but the changes were related to the level and duration of intake and the sex and initial serum lipid concentrations of the subjects.”1


1. Zhan S, et al. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile. Am J Clin Nutr. Mar 2005;81(2):397-408.