Effects of isoflavone supplements vs. soy foods on blood concentrations of genistein and daidzein in adults

Study design.

Average genistein and daidzein concentrations on the last day of 7 days of dosing for 12 adults who each followed three separate regimens in random order. The six time points were 0, 4, 8, 10, 12 and 24 h after initiating isoflavone intake with breakfast. Isoflavone intake occurred at three times/day (with breakfast, lunch and dinner), and the three separate regimens of isoflavones were soy foods (96 mg/day, 32 mg/dose — estimated from database isoflavone values); tablets—low dose (144 mg/day, 48 mg/tablet, one tablet/meal — determined by direct chemical analysis); or tablets—high dose (288 mg/day, 48 mg/tablet, two tablets/meal — determined by direct chemical analysis). Differences between sources/doses for genistein and daidzein were determined by repeated measures ANOVA. Pair-wise comparisons are presented as Bonferroni adjusted P values.