Soy protein rich in isoflavones (estrogen-like compounds) has been shown to prevent bone loss in ovariectomized rats. Our short-term preliminary study results in perimenopausal women are compelling, suggesting a bone-sparing effect. These findings have prompted great interest in isoflavones as an alternative to hormone replacement therapy, 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 early postmenopausal women by maintaining bone formation, being modulated by growth factors and isoflavone metabolism. The rationale for this research is that current hormone therapy is fraught with side effects that adversely affect women, resulting in non-compliance. This randomized double-blind placebo controlled clinical trial will examine the effects of two doses (80 or 120 mg/d) of isoflavone-rich soy extract on bone in non-osteoporotic early postmenopausal women (N=234).
Specific Aims are to: 1) Determine the bone-preserving effects of isoflavones on lumbar spine bone mass as the primary outcome; 2) Relate treatment-induced changes in bone mass to changes in biochemical markers of bone turnover; 3) 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, thus accounting for variability in response to treatment; 4) Ascertain the safety of isoflavone-rich soy extract. Caucasian women of European descent will be recruited at two sites (117 at IA, 117 at CA). Random effects repeated measures analyses will be used to: a) characterize change in bone mass as the primary outcome, b) estimate treatment-induced effects, and c) depict change in markers of bone turnover in relation to bone mass change. We will use intent-to-treat for the primary test. We will also examine potential modulators (reproductive hormones, IGF-I, plasma isoflavones) and account for other factors that affect bone, as indicated in specific aim 3. This study will provide valuable data on whether isoflavones impact bone in early postmenopausal women and help elucidate potential mechanisms, thereby contributing to our understanding of isoflavones as an alternative to traditional hormone therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR046922-04
Application #
6947256
Study Section
Epidemiology and Disease Control Subcommittee 2 (EDC)
Program Officer
Mcgowan, Joan A
Project Start
2002-05-24
Project End
2007-04-30
Budget Start
2005-05-01
Budget End
2006-11-30
Support Year
4
Fiscal Year
2005
Total Cost
$668,946
Indirect Cost
Name
Iowa State University
Department
Nutrition
Type
Other Domestic Higher Education
DUNS #
005309844
City
Ames
State
IA
Country
United States
Zip Code
50011
Alekel, D Lee; Genschel, Ulrike; Koehler, Kenneth J et al. (2015) Soy Isoflavones for Reducing Bone Loss Study: effects of a 3-year trial on hormones, adverse events, and endometrial thickness in postmenopausal women. Menopause 22:185-97
Shedd-Wise, Kristine M; Alekel, D Lee; Hofmann, Heike et al. (2011) The soy isoflavones for reducing bone loss study: 3-yr effects on pQCT bone mineral density and strength measures in postmenopausal women. J Clin Densitom 14:47-57
Gertz, E R; Silverman, N E; Wise, K S et al. (2010) Contribution of serum inflammatory markers to changes in bone mineral content and density in postmenopausal women: a 1-year investigation. J Clin Densitom 13:277-82
Alekel, D Lee; Van Loan, Marta D; Koehler, Kenneth J et al. (2010) The soy isoflavones for reducing bone loss (SIRBL) study: a 3-y randomized controlled trial in postmenopausal women. Am J Clin Nutr 91:218-30
Matvienko, Oksana A; Alekel, D Lee; Genschel, Ulrike et al. (2010) Appetitive hormones, but not isoflavone tablets, influence overall and central adiposity in healthy postmenopausal women. Menopause 17:594-601
Crist, Betsy L; Alekel, D Lee; Ritland, Laura M et al. (2009) Association of oxidative stress, iron, and centralized fat mass in healthy postmenopausal women. J Womens Health (Larchmt) 18:795-801
Stewart, Jeanne W; Alekel, D Lee; Ritland, Laura M et al. (2009) Serum 25-hydroxyvitamin D is related to indicators of overall physical fitness in healthy postmenopausal women. Menopause 16:1093-101
Perry, Courtney D; Alekel, D Lee; Ritland, Laura M et al. (2008) Centrally located body fat is related to inflammatory markers in healthy postmenopausal women. Menopause 15:619-27
Ritland, Laura M; Alekel, D Lee; Matvienko, Oksana A et al. (2008) Centrally located body fat is related to appetitive hormones in healthy postmenopausal women. Eur J Endocrinol 158:889-97
Shedd, Kristine M; Hanson, Kathy B; Alekel, D Lee et al. (2007) Quantifying leisure physical activity and its relation to bone density and strength. Med Sci Sports Exerc 39:2189-98

Showing the most recent 10 out of 11 publications