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Isoflavones significantly improve bone mineral density (BMD) and are safe in postmenopausal women, according to a systematic review and meta-analysis of 63 randomized controlled trials involving 6,427 postmenopausal women.
The review in the journal Osteoporosis International found the positive outcomes were primarily from two isoflavone formulations: genistein pure compound (54 mg/day) and synthetic ipriflavone (600 mg/day). The authors have an interest in the development of natural products for clinical use, including soy isoflavones.
“However, the results of various trials on the benefits of isoflavone interventions on BMD in postmenopausal women are inconsistent and some are even contradictory, resulting in inconclusive clinical implications,” said lead author Nut Koonrungsesomboon, MD, PhD, an assistant professor of pharmacology at Chiang Mai University in Thailand.
“We aimed to identify the formulation, dosage and duration of isoflavone interventions that are most likely to bring about clinical benefits to postmenopausal women.”
Three databases were searched: PubMed, Scopus and Cochrane Library, through September 2019, with no language restriction. Of the women included in the systematic review and meta-analysis, 3,187 were in the isoflavone (intervention) group and 3,240 in the non-isoflavone (control) group. Intervention duration ranged from 1 to 36 months.
Significant favorable outcomes from isoflavone interventions were observed on three common sites for osteoporotic fracture: the lumbar spine (mean difference (MD) = 21.34 mg/cm2; 95% confidence interval (CI): 8.21 to 34.47 mg/cm2; P = 0.001); the femoral neck (MD = 28.88 mg/cm2; 95% CI:15.05 to 42.71 mg/cm2, P <0.001); and the distal radius (MD = 19.27 mg/cm2; 95% CI: 5.65 to 32.89 mg/cm2; P = 0.006).
But the benefits of isoflavone extracts and dietary isoflavone supplements on BMD outcomes remain uncertain.
“I did not expect that genistein pure compounds and synthetic isoflavones would be the only formulations proven to be beneficial to postmenopausal women,” Dr. Koonrungsesomboon told Contemporary OB/GYN®.
“Thousands or millions of people around the world might have consumed dietary isoflavone products and perceived that they could receive some BMD benefits, despite the fact that they might not.”
Isoflavones were generally safe and well tolerated. No serious adverse events were reported in any of the included studies.
Isoflavoneshave a structure similar to 17β-estradiol and they act as estrogen agonists in a low-estrogen environment, such as in postmenopausal women, according to Dr. Koonrungsesomboon.
“It is well known that estrogen deficiency accelerates bone loss in postmenopausal women, so isoflavone interventions are supposed to be helpful in preventing and treating menopause-related osteoporosis,” he said.
Current evidence suggests that isoflavone extract or dietary isoflavone supplements may not help prevent bone loss in postmenopausal women.
“Rather, genistein pure compounds with a daily dosage of 54 mg or ipriflavone with a daily dosage of 600 mg hold great promise, either as a complementary or alternative option in the prevention and treatment of menopause-related osteoporosis, especially in those patients who are unable to tolerate the side effects of conventional therapies,” Dr. Koonrungsesomboon said.
Dr. Koonrungsesomboon reports no relevant financial disclosures.