British Journal of Nutrition

Research Article

Soya isoflavone-enriched cereal bars affect markers of endothelial function in postmenopausal women

J. Hallunda1 c1, S. Bügela1, T. Tholstrupa1, M. Ferraria2, D. Talbota3, W. L. Halla4, M. Reimanna5, C.M. Williamsa4 and N. Wiinberga6

a1 Department of Human Nutrition Centre for Advanced Food Studies The Royal Veterinary and Agricultural University Frederiksberg Denmark

a2 Human Nutrition Unit National Institute for Research on Food and Nutrition Rome Italy

a3 Unilever R&D Colworth Sharnbrook Bedfordshire UK

a4 Hugh Sinclair Unit of Human Nutrition School of Food Biosciences University of Reading Reading UK

a5 Dietary Fibre and the Metabolic Syndrome Group German Institute of Human Nutrition Potsdam-Rehbruecke Nuthetal Germany

a6 Department of Clinical Physiology and Nuclear Medicine Frederiksberg University Hospital Frederiksberg Denmark

Abstract

Soya isoflavones are thought to be cardioprotective due to their structural similarity to oestrogen. In order to investigate the effect of soya isoflavones on markers of endothelial function we conducted a randomised, double-blind, placebo-controlled, cross-over study with thirty healthy postmenopausal women. The women consumed cereal bars, with or without soya isoflavones (50mg/d), for 8 weeks, separated by an 8-week washout period. Systemic arterial complince (SAC), isobaric arterial compliance (IAC), flow-mediated endothelium-dependent vasodilation (FMD) and nitroglycerine-mediated endothelium-independent vasodilation (NMD) were measured at the beginning of the study and after each intervention period. Blood pressure (BP) and plasma concentrations of nitrite and nitrate (NOx) and endothelin-1 (ET-1) were measured at the beginning and end of each intervention period.NMD was 13·4 (sem 2·0) % at baseline and 15·5 (sem 1·1) % after isoflavone treatment compared with 12·4 (sem 1·0) % after placebo treatment (P=0·03). NOx increased from 27·7 (sem 2·7) to 31·1 (sem 3·2) μm after isoflavones treatment compared with 25·4 (sem 1·5) to 20·4 (sem 1·1) μm after placebo treatment (P=0·003) and a significant increase in the NOx:ET-1 ratio (P=0·005) was observed after the isoflavone treatment compared with placebo. A significant difference in SAC after the isoflavone and placebo treatment was observed (P=0·04). No significant difference was found in FMD, IAC, BP and ET-1. In conclusion, 8 weeks' consumption of cereals bars enriched with 50mg soya isoflavones/d increased plasma NOx concentrations and improved endothelium-independent vasodilation in healthy postmenopausal women.

(Received August 30 2005)

(Revised December 13 2005)

(Accepted December 20 2005)

Correspondence:

c1 *Corresponding author: Dr J. Hallund, fax +45 35282483, email jeha@kvl.dk

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