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Bone Response to Soy Isoflavones in Women (SIRBL)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT00043745
Recruitment Status : Completed
First Posted : August 14, 2002
Last Update Posted : February 7, 2013
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Information provided by (Responsible Party):
Dr. Manju B. Reddy, Iowa State University

Brief Summary:
This study will provide valuable data on whether soy isoflavones impact bone loss in postmenopausal women. The study will help clarify potential mechanisms and contribute to our understanding of isoflavones as an alternative to traditional hormone therapy.

Condition or disease Intervention/treatment Phase
Osteopenia Osteoporosis Dietary Supplement: Soy isoflavones Dietary Supplement: Extract tablets Phase 2

Detailed Description:
Soy protein, rich in isoflavones (estrogen-like compounds), has been shown to prevent bone loss in ovariectomized rats. Short-term preliminary study results in perimenopausal women suggest a bone-sparing effect. Great interest in isoflavones as an alternative to hormone replacement therapy has emerged, yet the long-term efficacy of isoflavones on bone in humans is unknown. Our objective is to determine the three-year efficacy of isoflavone-rich soy extract in attenuating bone loss in postmenopausal women. The central hypothesis is that soy isoflavones will attenuate bone loss in these women by maintaining bone formation, which is modulated by growth factors and isoflavone metabolism. The rationale for this research is that current hormone therapy is fraught with adverse side effects, resulting in non-compliance. This randomized, double-blind, placebo-controlled clinical trial will examine the effects of two doses (80 or 120 mg daily) of isoflavone-rich soy extract on bone in non-osteoporotic postmenopausal women (N=234). The specific aims of this study are: 1) to determine the bone-preserving effects of isoflavones on lumbar spine bone mineral density (BMD); 2) to relate treatment-induced changes in BMD to changes in biochemical markers of bone turnover; 3) to identify potential mechanisms by which isoflavones prevent or modulate bone loss by measuring endogenous estrogens, sex hormone-binding globulin, insulin-like growth factor-I (IGF-I), urinary minerals, serum 25(OH)vitamin D, plasma isoflavones and their metabolites, and customary intake of isoflavone-containing soy; and, 4) to ascertain the safety of isoflavone-rich soy extract. Postmenopausal women will be recruited at two sites (117 at Iowa, 117 at California). Random effects repeated measures analyses will be used to characterize change in BMD as the primary outcome, estimate treatment-induced effects, and depict change in markers of bone turnover in relation to BMD change. We will use intent-to-treat for the primary test, but also account for potential modulators (reproductive hormones, IGF-I, plasma isoflavones) that affect bone, as indicated in specific aim 3.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 224 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Prevention
Official Title: Bone Response to Soy Isoflavones in Women
Study Start Date : March 2003
Actual Primary Completion Date : April 2008

Arm Intervention/treatment
Experimental: 1
Participants will receive moderate dose soy isoflavone (80 mg/day) tablets, extracted from soy protein
Dietary Supplement: Soy isoflavones
Soy isoflavones extracted from soy protein, compressed into tablets; three tablets taken daily

Experimental: 2
Participants will receive high dose soy isoflavone (120 mg/day) tablets, extracted from soy protein
Dietary Supplement: Soy isoflavones
Soy isoflavones extracted from soy protein, compressed into tablets; three tablets taken daily

Placebo Comparator: 3
Participants will receive soy extract devoid of isoflavones to serve as placebo
Dietary Supplement: Extract tablets
Extract from soy protein, but devoid of isoflavones; three tablets taken once daily

Primary Outcome Measures :
  1. Lumbar spine bone mineral density [ Time Frame: Year 3 ]

Secondary Outcome Measures :
  1. Proximal femur bone mineral density [ Time Frame: Year 3 ]

Information from the National Library of Medicine

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Ages Eligible for Study:   45 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   Female
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Early postmenopausal (i.e., no menses during past 12 months) women, with an upper limit of 10 years since their last cycle
  • Natural menopause (i.e., no hysterectomies or oophorectomies)
  • Body mass index (BMI) > 20 and < 30

Exclusion Criteria:

  • Current or previous (within 12 months) use of hormone replacement therapy, hormonal contraceptives, estrogens, or progestogens
  • Current use of pharmacologic agents, such as selective estrogen-receptor modulators (SERMs) (e.g., raloxifene or tamoxifen) or anti-resorptive agents (e.g., alendronate or calcitonin), herbal therapies that may have estrogenic effects (e.g., herbimycin, tryphostins), or cigarettes
  • Strict vegans (but will include lacto-ovo-, lacto-, and ovo-vegetarians)
  • Metabolic bone disease, renal disease, history of urolithiasis, cancer, cardiovascular disease, diabetes mellitus, respiratory disease, gastrointestinal disease, liver disease, or other chronic diseases
  • First-degree relative with breast cancer
  • Lumbar spine BMD >= -1.5 standard deviations (SD) below mean (high-risk for osteoporosis) and BMD >= +1.0 SD above mean

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT00043745

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United States, California
USDA/ARS/WHNRC University of California-Davis
Davis, California, United States, 95616
United States, Iowa
Iowa State University
Ames, Iowa, United States, 50011
Sponsors and Collaborators
Iowa State University
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
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Principal Investigator: D. Lee Alekel, PhD Iowa State University

Publications automatically indexed to this study by Identifier (NCT Number):
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Responsible Party: Dr. Manju B. Reddy, Professor, Iowa State University Identifier: NCT00043745    
Other Study ID Numbers: R01AR046922 ( U.S. NIH Grant/Contract )
R01AR046922 ( U.S. NIH Grant/Contract )
First Posted: August 14, 2002    Key Record Dates
Last Update Posted: February 7, 2013
Last Verified: February 2013
Keywords provided by Dr. Manju B. Reddy, Iowa State University:
alternative hormone therapy
bone loss
Additional relevant MeSH terms:
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Bone Diseases, Metabolic
Bone Diseases
Musculoskeletal Diseases
Metabolic Diseases