FIGURE 13.8 Effect of diet with isoflavones extracted [soy (-)] versus soy containing isofla-vones [soy (+)] on coronary artery dilation in premenopausal female monkeys. Data expressed as percent change in vessel diameter from baseline +/- SEM. (Modified from Honoré, E.K. et al., Fertil. Steril, 67, 148, 1997. With permission.)
dilated (~6% change in diameter) after acetylcholine infusion while arteries of those fed soy (-) constricted (—6% change in diameter).45 Interestingly, intravenous administration of genistein into the left main coronary arteries of the monkeys fed soy (-) caused arterial dilation. A similar finding in premenopausal women was reported by Walker et al. (2001); intravenous administration of genistein into the brachial artery caused dilation.46
Our group observed that arterial dilation following acetylcholine perfusion could not be demonstrated in postmenopausal monkeys with low plasma estrogen concentrations (<5 pg/ml; unpublished data). However, as depicted in Figure 13.9, Williams et al. (2001) reported that when postmenopausal monkeys were treated with estradiol (equivalent to a woman's dose of 1 mg/day), their arteries dilated (~5%).47 Furthermore, when a combined treatment of estradiol and soy (129 mg/day equivalent to woman's dose) was given, the arteries responded with greater degrees of dilation (~12%) than with either treatment alone, indicating a significant (p < 0.05) interactive effect of soy and estradiol on vascular reactivity.
Soy's effects on vascular reactivity in postmenopausal women, as measured by flow-mediated dilation (FMD) of the brachial artery, appear to be minimal. In a comprehensive study by Teede et al. (2001), there was no significant increase in brachial artery flow mediated dilation in postmenopausal women consuming soy
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