A meal enriched with soy isoflavones increases nitric oxide-mediated vasodilation in healthy postmenopausal women.
Evidence from infusion studies suggests that soy isoflavones influence nitric oxide-dependent vasorelaxation. It is uncertain whether orally consumed isoflavones have similar effects. Healthy postmenopausal women (n = 22) consumed 2 low-fat test meals in random order 1 wk apart, with 80 mg isoflavones (ISO) or without isoflavones (CON). Endothelium-dependent vasodilation, assessed by brachial artery flow-mediated dilatation (FMD), was measured in fasting subjects, and 4 and 6 h following the test meal, in addition to blood pressure and pulse wave analysis to derive the peripheral augmentation index (pAIx). Blood samples were taken after fasting, and 5 and 7 h following the test meal for serum isoflavone, plasma 8-isoprostane F(2alpha), nitric oxide metabolites (NOx), glucose, and triacylglycerol analysis. Serum genistein and daidzein concentrations (geometric mean, 95% CI) reached 1.49 (1.20-1.84) micromol/L and 0.95 (0.70-1.30) micromol/L, respectively, following ISO (7 h). FMD and plasma NOx concentrations were greater following ISO compared with CON, indicating better postprandial endothelial function. FMD values (%, mean +/- SD) were: CON, 5.49 +/- 2.32, 4.35 +/- 2.32, 4.40 +/- 2.26; ISO, 5.38 +/- 1.91, 5.08 +/- 1.74, 6.11 +/- 2.60, at baseline, 4 h, and 6 h, respectively (P < 0.01). Plasma NOx concentrations (micromol/L, mean +/- SD) were: CON, 20.0 +/- 5.1, 16.8 +/- 5.1, 23.1 +/- 6.0; ISO, 18.6 +/- 6.3, 19.5 +/- 5.1, 21.3 +/- 10.1, at baseline, 5 h, and 7 h, respectively (P < 0.005). Treatment did not affect pAIx, blood pressure, or plasma 8-isoprostane F(2alpha) concentrations. In conclusion, consuming an isoflavone-enriched low-fat meal acutely increases endothelium-dependent vasodilation in postmenopausal women. Regular consumption of soy isoflavones may protect against endothelial dysfunction.
Nutritional Sciences Division, School of Biomedical and Health Sciences, King's College London, London SE1 9NH, UK. wendy.hall@kcl.ac.uk
Wendy L
WL
Hall
Nichola L
NL
Formanuik
Duangporn
D
Harnpanich
Monique
M
Cheung
Duncan
D
Talbot
Philip J
PJ
Chowienczyk
Thomas A B
TA
Sanders
D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D001916:Brachial Artery / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D028421:Isoprostanes / Q000097:blood; D008593:Menopause / Q000097:blood / Q000502:physiology; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood / Q000502:physiology; D045730:Soy Foods / Q000032:analysis; D014280:Triglycerides / Q000097:blood; D014664:Vasodilation / Q000502:physiology*
D001786:Blood Glucose; D007529:Isoflavones; D028421:Isoprostanes; D014280:Triglycerides; D009569:Nitric Oxide