Urinary excretion of equol by postmenopausal women consuming soymilk fermented by probiotic bifidobacteria

Objective: To study the effects of consuming isoflavone aglycone-enriched soymilk fermented by bifidobacteria on urinary excretion of equol with respect to fermentation, daidzein dose, supplementation duration and background diet. Design: Double-blind crossover pilot study comprising three 14-day supplementation periods separated by a washout. Setting: Victoria University, Melbourne, Australia. Subjects: Sixteen postmenopausal women. Intervention: Subjects randomized into two groups consuming either fermented (FS) or non-fermented soymilk (NFS), ingested three daily dosages of daidzein via soymilk and collected pooled urine specimens. Daidzein and equol were quantified using high-performance liquid chromatography. Results: After 14-days supplementation six women (38%) excreted equol (>1 μmol equol/day), including four from the FS group, two of whom were classified as non-producers at day 4. Bifidobacteria ingestion, composition of daidzein and its glucosides, and carbohydrate intake appeared to influence equol formation among equol producers. Conclusions: Pilot-study group mean urinary equol excretion results provided insufficient evidence (P>0.05) that FS consumption instigates equol production in women predetermined as non-producers. Sponsorship: Australian Research Council's Strategic Partnership with Industry (Sanitarium Health Food Company) for Research and Training.