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Randomized controlled trial of whole soy and isoflavone daidzein on menopausal symptoms in equol-producing Chinese postmenopausal women

Liu, Zhao-min PhD1; Ho, Suzanne C. PhD2; Woo, Jean MD1; Chen, Yu-ming PhD3; Wong, Carmen MD4

doi: 10.1097/GME.0000000000000102
Original Articles

Objective: Dietary supplements containing soy or isoflavones are widely used as alternatives to hormone therapy. However, their efficacy is still inconclusive, and limited data on equol producers are available. The aim of this study was to examine the effect of whole soy (soy flour) or purified daidzein (one major soy isoflavone and the precursor of equol) on menopausal symptoms in equol-producing postmenopausal women, a population most likely to benefit from soy intervention.

Methods: This is a 6-month parallel-group, double-blind, randomized, placebo-controlled trial. Two hundred seventy equol-producing prehypertensive Chinese postmenopausal women were randomized to one of three treatment groups: 40 g of soy flour (whole soy group), 40 g of low-fat milk powder + 63 mg of daidzein (daidzein group), or 40 g of low-fat milk powder (placebo group) daily, each given as a solid beverage for 6 months. Changes in menopausal symptoms were assessed by a validated and structured symptom checklist at baseline and 6 months.

Results: Two hundred fifty-three participants completed the study according to protocol. Urinary isoflavones indicated good compliance with the interventions. Baseline menopausal symptoms were comparable among the three study groups. Intention-to-treat analysis indicated that there was no significant difference in the 6-month changes or percent changes in the total number of menopausal symptoms, in the five dimensions of symptoms, and in the frequencies of individual symptoms among the three treatment groups.

Conclusions: Whole soy and purified daidzein have no significant effect on alleviation of menopausal symptoms among equol-producing postmenopausal women with prehypertension.

From the 1Department of Medicine and Therapeutics, and 2Division of Epidemiology, The Jockey Club of the School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR; 3Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, PR China; and 4Center of Research and Promotion of Women’s Health, The Jockey Club of the School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR.

Received July 17, 2013; revised and accepted August 22, 2013.

S.C.H., Y.m.C., Z.m.L., and J.W. conceptualized and designed the trial and obtained the grant. Z.m.L. collected and analyzed the data and drafted the manuscript. Y.m.C. participated in the urinary analysis of isoflavones and dietary assessment. All authors contributed to manuscript preparation. Z.m.L. had full access to the data and takes responsibility for the integrity of the data and the accuracy of data analysis. All authors read and approved the final version of the manuscript.

Neither the Research Grant Committee General Research Fund nor the soy and dairy company had any role in the design and conduct of the study; the collection, analysis, and interpretation of data; or the preparation, review, or approval of the manuscript.

Funding/support: This study was funded by the Hong Kong Research Grant Committee General Research Fund (RGC-GRF465810) and registered with (identifier NCT01270737;

Financial disclosure/conflicts of interest: None reported.

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Address correspondence to: Zhao-min Liu, PhD, Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR. E-mail:

© 2014 by The North American Menopause Society.