Effect of Lactobacillus sporogenes on oral isoflavones bioavailability: single dose pharmacokinetic study in menopausal women.

PURPOSE OF THE STUDY To verify the single dose bioavailability of two oral formulations of soy isoflavones, with and without lactobacilli, in menopausal women in antibiotic therapy. METHODS Twelve menopause women (mean age 54.3 years, BMI 25.0 kg/m2) participated in a controlled cross-over study. Reference and test treatments were: R = tablets containing soy isoflavones 60 mg (genistin 30 mg + daidzin 30 mg) + calcium and vitamin D3; E = R + 500 million vital spores of Lactobacillus sporogenes (E is Estromineral, a food supplement containing soy isoflavones 60 mg, calcium 141 mg and vitamin D3 5 microg). The design included 2 periods of 5 days of amoxicillin + clavulanate treatment with a 2-week wash-out. After each period alternatively a single dose of each formulation was given in randomised sequence. Genistein and daidzein were determined in plasma by HPLC, sampled 10 times within 24 h after dosing. RESULTS Genistein pharmacokinetics parameters were higher after E than after R administration: peak plasma concentration (Cmax) +24.3%, area under the concentration curve (AUC0-24) +24.4% and mean residence time +11.0%. Daidzein Cmax and AUC showed a larger variability on R, evidenced by higher scatter from the mean on the formulation without lactobacilli. CONCLUSION A trend is shown for a greater absorption of genistein from a formulation containing lactobacilli.