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.
Hall
Wendy L
WL
Nutritional Sciences Division, School of Biomedical and Health Sciences, King's College London, London SE1 9NH, UK. wendy.hall@kcl.ac.uk
Formanuik
Nichola L
NL
Harnpanich
Duangporn
D
Cheung
Monique
M
Talbot
Duncan
D
Chowienczyk
Philip J
PJ
Sanders
Thomas A B
TA
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