Correlation between equol production and intestinal microbiota after treatment with isoflavone, isoflavone plus probiotic and hormonal therapy in postmenopausal women: a pilot study

OBJECTIVES: To correlate the urinary excretion of equol with intestinal microbiota in response to isoflavone supplementation alone or in combination with probiotics, and to compare these results with those of hormone therapy in postmenopausal women. METHODS: A pilot study was conducted on 47 postmenopausal women aged 40-60 years. Participants were randomly assigned to one of three groups: (A) oral isoflavone (150 mg dry extract of Glycine max); (B) isoflavone plus probiotic (Lactobacillus acidophilus, Lactobacillus casei, Lactococcus lactis, Bifidobacterium bifidum, and Bifidobacterium lactis); or (C) hormone therapy (1 mg estradiol/0.5 mg norethisterone acetate). Fecal samples were collected to extract bacterial DNA, and equol and its intermediates were measured using gas chromatography coupled with mass spectrometry at baseline and after 16 weeks of treatment. RESULTS: In the isoflavone alone and isoflavone plus probiotic groups, no statistically significant correlations were found between bacterial phyla or genera and the urinary excretion of equol or its intermediate after 16 weeks of treatment. In the hormone therapy group, directly proportional correlation between Bacteroidetes (Spearman R=0.83, Pa=0.01), Cyanobacteria (Spearman R=0.89, Pa=0.002), Alistipes (Spearman R=0.81, Pa=0.04), Catenibacterium (Spearman R=0.81, Pa=0.04), Clostridium (Spearman R=0.84, Pa=0.02), Barnesiella (Spearman R=0.84, Pa=0.02), and the urinary excretion of the equol intermediate were observed. CONCLUSIONS: Only the hormone therapy group showed a significant increase in bacterial abundance involved in isoflavone metabolism.