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    1 Comment for this article
    Soy Isoflavone Extracts are not the Same as Whole Soy
    Michal R. Pijak, MD | Slovak Medical University, Bratislava, Slovakia,
    In our opinion, the study by Levis et al. (1) does not prove whether or not soy consumption or soy products are beneficial in the prevention of osteoporosis or postmenopausal symptoms because isoflavone extracts (not soy protein or foods containing isoflavones) were used. Soy isoflavone extracts are not the same as whole soy beans. Furthermore, the study had several flaws. First, the population of women in the first 5 years of menopause, on average, had low rates of bone loss. Hence, the sample size was too small and the duration of the treatment too short. Indeed, as noted in an accompanying editorial, only 248 of an expected 306 participants were enrolled and far more participants dropped out than was predicted. Moreover, according to current guidelines, women who have such a slow rate of bone loss are not indicated for any treatment. Second, the dose of 200 mg of soy isoflavone tablets taken once daily could be too high. Currently, 40 to 50 mg of isoflavones (biochanin A, daidzein, formononetin and genistein) are recommended as daily intake. This recommendation is based on the daily intake of phytoestrogens in a traditional Japanese diet. In sum, the results of this study do not provide evidence for the efficacy of soy isoflavones in the treatment of menopausal bone density loss or symptoms. The study does show that caution is needed when using only one component of the whole food and that unnatural processed products like these soy pills may cause side effects (increased frequency of constipation in the reported soy pill group). 1. Levis S, Strickman-Stein N, Ganjei-Azar P, Xu P, Doerge DR, Krischer J. Soy Isoflavones in the Prevention of Menopausal Bone Loss and Menopausal Symptoms: A Randomized, Double-blind Trial. Arch Intern Med. 2011;171:1363 -9.

    Conflict of Interest: None declared
    Original Investigation
    Aug 9 2011

    Soy Isoflavones in the Prevention of Menopausal Bone Loss and Menopausal Symptoms: A Randomized, Double-blind Trial

    Author Affiliations

    Author Affiliations: Geriatric Research, Education, and Clinical Center, Miami Veterans Affairs Healthcare System, and Departments of Medicine (Dr Levis), Epidemiology (Dr Strickman-Stein), and Pathology (Dr Ganjei-Azar), Miller School of Medicine, University of Miami, Florida; Department of Pediatrics, University of South Florida, Tampa (Ms Xu and Dr Krischer); and National Center for Toxicological Research, US Food and Drug Administration, Jefferson, Arkansas (Dr Doerge).

    Arch Intern Med. 2011;171(15):1363-1369. doi:10.1001/archinternmed.2011.330

    Background Concerns regarding the risk of estrogen replacement have resulted in a significant increase in the use of soy products by menopausal women who, despite the lack of evidence of the efficacy of such products, seek alternatives to menopausal hormone therapy. Our goal was to determine the efficacy of soy isoflavone tablets in preventing bone loss and menopausal symptoms.

    Methods  The study design was a single-center, randomized, placebo-controlled, double-blind clinical trial conducted from July 1, 2004, through March 31, 2009. Women aged 45 to 60 years within 5 years of menopause and with a bone mineral density T score of −2.0 or higher in the lumbar spine or total hip were randomly assigned, in equal proportions, to receive daily soy isoflavone tablets, 200 mg, or placebo. The primary outcome was changes in bone mineral density in the lumbar spine, total hip, and femoral neck at the 2-year follow-up. Secondary outcomes included changes in menopausal symptoms, vaginal cytologic characteristics, N -telopeptide of type I bone collagen, lipids, and thyroid function.

    Results After 2 years, no significant differences were found between the participants receiving soy tablets (n = 122) and those receiving placebo (n = 126) regarding changes in bone mineral density in the spine (−2.0% and −2.3%, respectively), the total hip (−1.2% and −1.4%, respectively), or the femoral neck (−2.2% and −2.1%, respectively). A significantly larger proportion of participants in the soy group experienced hot flashes and constipation compared with the control group. No significant differences were found between groups in other outcomes.

    Conclusions In this population, the daily administration of tablets containing 200 mg of soy isoflavones for 2 years did not prevent bone loss or menopausal symptoms.

    Trial Registration  clinicaltrials.gov Identifier: NCT00076050