British Journal of Nutrition

Full Papers

Dietary soya intake alters plasma antioxidant status and lipid peroxidation in postmenopausal women with the metabolic syndrome

Leila Azadbakhta1a2 c1, Masoud Kimiagara3, Yadollah Mehrabia4, Ahmad Esmaillzadeha1a2, Frank B. Hua5a6 and Walter C. Willetta5a6

a1 Department of Nutrition, School of Health, Isfahan University of Medical Sciences, Isfahan, PO Box 81745, Iran

a2 Nutrition Research Center, Isfahan University of Medical Sciences, Isfahan, Iran

a3 Department of Human Nutrition, School of Nutrition and Food Science, Shaheed Beheshti University of Medical Sciences, Tehran, Iran

a4 School of Public Health, Shaheed Beheshti University of Medical Sciences, Tehran, Iran

a5 Department of Nutrition, Harvard School of Public Health, Boston, MA, USA

a6 Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA

Abstract

Postmenopausal women with the metabolic syndrome are at high risk of oxidative stress. Several studies have suggested possible antioxidant properties of soya, but little evidence is available regarding the effect of soya on oxidative stress in postmenopausal women with the metabolic syndrome. The objective of the present study was to determine the effects of soya consumption on plasma total antioxidant capacity (TAC) and malondialdehyde (MDA) level in postmenopausal women with the metabolic syndrome. A randomised cross-over trial was undertaken on forty-two postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control (Dietary Approaches to Stop Hypertension; DASH) diet, a soya protein diet, or a soya nut diet, each for 8 weeks. Red meat in the DASH diet (one serving per d) was replaced by soya protein in the soya protein period and by soya nuts in the soya nut period. Significant differences between the end values of the control diet, soya protein diet and soya nut diet were seen for MDA (0·70, 0·64 and 0·63 μmol/l; global P < 0·01). The results also showed a significant difference between the end values for TAC (1950, 2030 and 2110 μmol/l, respectively; P < 0·01). The difference from control for TAC was +4·5 % (P < 0·01) in the soya nut period and +5·8 % (P < 0·01) in the soya protein regimen. Both soya nuts and soya protein decreased MDA significantly compared with the control diet (difference from control was − 7·9 % (P < 0·01) in the soya nut period and − 9·4 % (P < 0·01) in the soya protein diet). We conclude that soya consumption reduces plasma MDA and increases plasma TAC levels in postmenopausal women with the metabolic syndrome.

(Received January 03 2007)

(Revised March 07 2007)

(Accepted March 30 2007)

Correspondence:

c1 Corresponding author: Dr Leila Azadbakht, fax +98 311 6682509, email azadbakht@hlth.mui.ac.ir

Footnotes

Abbreviations: DASH, Dietary Approaches to Stop Hypertension; MDA, malondialdehyde; TAC, total antioxidant capacity