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Davis, California 95616


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.

Study summary:

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.


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

Study is Available At:

Original ID:

R01 AR46922



Secondary ID:


Study Acronym:


Brief Title:

Bone Response to Soy Isoflavones in Women

Official Title:

Bone Response to Soy Isoflavones in Women

Overall Status:


Study Phase:

Phase 2



Minimum Age:

45 Years

Maximum Age:

65 Years

Quick Facts

Healthy Volunteers
Oversight Has DMC
Study Is FDA Regulated
Study Is Section 801
Has Expanded Access

Study Source:

Iowa State University

Oversight Authority:

United States: Federal Government

Reasons Why Stopped:

Study Type:


Study Design:

Allocation: Randomized, Endpoint Classification:

Number of Arms:


Number of Groups:


Total Enrollment:


Enrollment Type:


Overall Contact Information

Official Name:D. Lee Alekel, PhD
Principal Investigator
Iowa State University

Study Dates

Start Date:March 2003
Primary Completion Date:April 2008
Primary Completion Type:Actual
Verification Date:February 2013
Last Changed Date:February 6, 2013
First Received Date:August 13, 2002

Study Outcomes

Outcome Type:Primary Outcome
Measure:Lumbar spine bone mineral density
Time Frame:Year 3
Safety Issues:True
Outcome Type:Secondary Outcome
Measure:Proximal femur bone mineral density
Time Frame:Year 3
Safety Issues:True

Study Interventions

Intervention Type:Dietary Supplement
Name:Soy isoflavones
Description:Soy isoflavones extracted from soy protein, compressed into tablets; three tablets taken daily
Arm Name:1
Intervention Type:Dietary Supplement
Name:Extract tablets
Description:Extract from soy protein, but devoid of isoflavones; three tablets taken once daily
Arm Name:3

Study Arms

Study Arm Type:Experimental
Arm Name:1
Description:Participants will receive moderate dose soy isoflavone (80 mg/day) tablets, extracted from soy protein
Study Arm Type:Experimental
Arm Name:2
Description:Participants will receive high dose soy isoflavone (120 mg/day) tablets, extracted from soy protein
Study Arm Type:Placebo Comparator
Arm Name:3
Description:Participants will receive soy extract devoid of isoflavones to serve as placebo

Study Agencies

Agency Class:Other
Agency Type:Lead Sponsor
Agency Name:Iowa State University
Agency Class:NIH
Agency Type:Collaborator
Agency Name:National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)

Sample and Retention Information

There are no available Sample and Retention Information

Study References

There are no available Study References

Data Source: ClinicalTrials.gov

Date Processed: January 21, 2020

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