Supplementation with a Probiotic Formula Having β-Glucuronidase Activity Modulates Serum Estrogen Levels in Healthy Peri- and Postmenopausal Women

Declines in estrogen levels occur in women transitioning to menopause. Estrogen hormones play important roles in multiple systems of the body, and estrogen loss is associated with a variety of symptoms that can decrease quality of life. The gut microbiota is involved in regulating endogenous estrogen levels. A portion of estrogen glucuronides can be reactivated in the gut by the microbial enzyme β-glucuronidase, and the resulting free estrogens can return to the bloodstream. Here, we carried out <i>in vitro</i> screening of β-glucuronidase activities for 84 strains belonging to 16 different species of lactic acid bacteria and bifidobacteria and found that one and three strains of <i>Levilactobacillus brevis</i> and <i>Lacticasebacillus rhamnosus</i>, respectively, can deconjugate estrogens. Among these strains, <i>L. brevis</i> KABP052 had the highest β-glucuronidase activity. Moreover, in an exploratory, randomized, double-blind, placebo-controlled trial, we demonstrated that serum estrogen levels in healthy peri- and postmenopausal women given a probiotic formula containing KABP052 were maintained over time, whereas levels significantly decreased in the group given a placebo. Significantly higher levels of estradiol (31.62 ± 7.97 pg/mL vs. 25.12 ± 8.17 pg/mL) and estrone (21.38 ± 8.57 pg/mL vs. 13.18 ± 8.77 pg/mL) were observed in the probiotic versus placebo group after 12 weeks of intervention. This clinical study demonstrated for the first time the estrogen modulation capacity of a probiotic formula containing a bacterial strain having β-glucuronidase activity in women during the menopausal transition and formed the basis for future investigations using probiotics in the menopausal population.