Nutrients. 2019 Nov 4;11(11). pii: E2649. doi: 10.3390/nu11112649.
Isoflavones have gained popularity as an alternative treatment for menopausal symptoms for people who cannot or are unwilling to take hormone replacement therapy. However, there is still no consensus on the effects of isoflavones despite over two decades of vigorous research. This systematic review aims to summarize the current literature on isoflavone supplements, focusing on the active ingredients daidzein, genistein, and S-equol, and provide a framework to guide future research. We performed a literature search in Ovid Medline using the search terms «isoflavone» and «menopause», which yielded 95 abstracts and 68 full-text articles. We found that isoflavones reduce hot flashes even accounting for placebo effect, attenuate lumbar spine bone mineral density (BMD) loss, show beneficial effects on systolic blood pressure during early menopause, and improve glycemic control in vitro. There are currently no conclusive benefits of isoflavones on urogenital symptoms and cognition. Due to the lack of standardized research protocols including isoflavone component and dosage, outcomes, and trial duration, it is difficult to reach a conclusion at this point in time. Despite these limitations, the evidence thus far favors the use of isoflavones due to their safety profile and benefit to overall health.
In the literature we reviewed, isoflavones reduce hot flashes even accounting for placebo e_ect, attenuate lumbar spine BMD loss, may show beneficial e_ects on systolic blood pressure during early menopause, and may improve glycemic control in vitro. On the other hand, the e_ect of isoflavones on GPER positive cells should be further explored. There are currently no conclusive benefits of isoflavones on urogenital symptoms and cognition.
Although isoflavones will never be as e_ective as hormone therapy in relieving menopausal symptoms, a survey found that 70% of women would be “satisfied with a nonhormonal intervention that provided at least a 50% reduction in hot flashes” . The safety profile of isoflavones combined with their benefit to overall health makes them a compelling treatment option for postmenopausal women unwilling or unable to take hormone replacement therapy.
In order to minimize study heterogeneity in future research, we urge standardization of the many variables involved in isoflavone trials, such as the time to menopause that may have crucial e_ect on the isoflavone response. Isoflavone aglycone content should be consistent across trials for better communication, prediction of therapeutic activity, and ensure reproducibility. In addition, outcome measures and study duration should be standardized, along with the metabolic profiles of participants. Finally, bigger sample sizes are needed to increase the validity and generalizability of results.