An isoflavone metabolite reduces arterial stiffness and blood pressure in overweight men and postmenopausal women

Objectives Isoflavones reduce arterial stiffness, a predictor of cardiovascular events. Whether metabolites of isoflavones have similar bioactivity is unknown. The effect of supplemental trans-tetrahydrodaidzein (THD) a metabolite of daidzein on pulse wave velocity (PWV), a measure of arterial stiffness was tested in overweight men and postmenopausal women. Methods 25 subjects, 11 postmenopausal women, 14 men (age, 57 [7] years; body mass index, 30.3 [4.7] kg/m2; mean [S.D.]) participated in a double-blind, randomized, cross-over trial of THD versus placebo. Design: 2 weeks run-in followed by either THD 1 g daily or placebo, each intervention 5 weeks. Aorta–femoral artery PWV, blood pressure and plasma lipids were measured after run-in, THD and placebo. Results PWV was significantly reduced (signifying diminished central arterial stiffness): medians (25th and 75th%), placebo 9.9 m/s (8.7, 11.1), THD 8.8 m/s (7.9, 10.9); RM ANOVA P = 0.023, with Tukey procedure P < 0.05. Systolic blood pressure was significantly reduced: means (S.D.), placebo 125.6 (14.7), THD 121.3 (12.2) mmHg; Tukey P < 0.05. Plasma cholesterol, triglyceride and LDL cholesterol did not differ significantly. Absorption of THD >80% substantially exceeded that of parent isoflavones. Conclusion A metabolite normally formed after consumption of isoflavones (formononetin, daidezein), taken orally, reduced blood pressure and central arterial stiffness indicating reduced cardiovascular risk.