Soy inclusion in the diet improves features of the metabolic syndrome: a randomized crossover study in postmenopausal women1–3
Leila Azadbakht, Masoud Kimiagar, Yadollah Mehrabi, Ahmad Esmaillzadeh, Mojgan Padyab, Frank B Hu, and Walter C Willett
ABSTRACT Background: Little evidence exists regarding the effects of soy consumption on the metabolic syndrome in humans. Objective: We aimed todetermine the effects of soy consumption on components of the metabolic syndrome, plasma lipids, lipoproteins, insulin resistance, and glycemic control in postmenopausal women with the metabolic syndrome. Design: This randomized crossover clinical trial was undertaken in 42 postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control diet (DietaryApproaches to Stop Hypertension, DASH), a soy-protein diet, or a soy-nut diet, each for 8 wk. Red meat in the DASH period was replaced by soy-protein in the soy-protein period and by soy-nut in the soy-nut period. Results: The soy-nut regimen decreased the homeostasis model of assessment-insulin resistance score significantly compared with the soy-protein (difference in percentage change: 7.4 0.8; P 0.01) or control ( 12.9 0.9; P 0.01) diets. Consumption of soy-nut also reduced fasting plasma glucose more significantly than did the soy-protein ( 5.3 0.5%; P 0.01) or control ( 5.1 0.6%; P 0.01) diet. The soy-nut regimen decreased LDL cholesterol more than did the soy-protein period ( 5.0 0.6%; P 0.01) and the control ( 9.5 0.6%; P 0.01) diet. Soy-nut consumption significantly reducedserum C-peptide concentrations compared with control diet ( 8.0 2.1; P 0.01), but consumption of soy-protein did not. Conclusion: Short-term soy-nut consumption improved glycemic control and lipid profiles in postmenopausal women with the metabolic syndrome. Am J Clin Nutr 2007;85:735– 41. KEY WORDS Metabolic syndrome, insulin resistance, soy, glycemic control, lipid profiles INTRODUCTIONunsaturated fatty acids (8), n–3 fatty acids (9), dairy products (10), and whole grains (11) appeared to influence the prevalence of this syndrome, either positively or negatively, but little emphasis has been placed on the specific therapeutic diets that control the metabolic syndrome. In choosing a therapeutic diet, high amounts of vegetables, fruits, legumes, whole grains, lowfat dairy foods, and lowamounts of saturated fat and salt have been used in previous studies (12–15). Foods that improve insulin sensitivity might also modulate the metabolic abnormalities linked with insulin resistance (16). Many studies have reported beneficial effects of soy consumption on human health, but most of these investigations have been conducted among type 2 diabetic or hypercholesterolemic patients (16–19), or healthy subjects (20). Although some studies have reported effects of soy consumption on the metabolic syndrome in animals (21, 22), to our knowledge no reports are available regarding the effects of soy intake on features of the metabolic syndrome in humans. Soy consumption could reduce the risk of the metabolic syndrome through its beneficial components, including complex carbohydrates,unsaturated fatty acids, vegetable protein, soluble fiber, oligosaccharides, vitamins, minerals, inositol-derived substances such as lipintol and pinitol, and phytoestrogens, particularly the isoflavones genistein, diadzein, and glycitein (23–28). However, the amount and kind of these components may vary in different kinds of soy products; ie, textured soy-protein or soy-nut. We evaluated the effectsof soy consumption (in the form of soy-protein and unsalted soy-nut) on features of the metabolic syndrome, including plasma lipids, lipoproteins, insulin resistance, and glycemic control, in postmenopausal women with the metabolic syndrome.
1 From the Department of Human Nutrition, School of Nutrition and Food Science (LA, MK, and AE), and the School of Public Health (YM and MP), Shaheed...
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