STUDY:

JOURNAL: Am J Clin Nutr. 2002;76:365-372

AUTHORS: David J. A. Jenkins

ABSTRACT: Compared with a dairy diet, a soy-based diet improved lipid profile, yielding a calculated reduction in coronary artery disease (CAD) risk, according to a study published in the American Journal of Clinical Nutrition.

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COMMENTARY: "Many of the benefits of soy have been attributed to soy isoflavones," write David J. A. Jenkins, from St. Michael's Hospital in Toronto, Ontario, and colleagues.

Study subjects included 23 men and 18 postmenopausal women with elevated cholesterol levels who rotated through three one-month diets that were all very low in saturated fat (less than 5% of energy and less than 50 mg/day of cholesterol). Protein sources were low-fat dairy products and egg substitute in the control diet, and low-fat soymilk and a variety of soy-based meat substitutes such as soy hot dogs and tofu burgers in the two soy protein-containing diets. The high-isoflavone diet contained 50 g soy protein and 73 mg isoflavones daily, and the low-isoflavone diet contained 52 g soy protein and 10 mg isoflavones daily.

Although serum concentrations of low-density lipoprotein (LDL) cholesterol were lower after the high-isoflavone diet, there were no major differences between the high- and low-isoflavone soy protein diets in their beneficial effects. After each soy diet, total cholesterol, LDL to high-density lipoprotein (HDL) ratio cholesterol, homocysteine concentrations, and systolic blood pressure in men were lower than they were after the control diet. Overall CAD risk calculated from blood lipid and blood pressure changes was 10.1%+/-2.7% lower with the soy diets than with the control diet.