title: Usual dietary isoflavone intake, bone mineral density, and bone metabolism in postmenopausal women.
abstract: Clinical trials of isoflavone supplementation and bone density have been of relatively short duration and yielded inconsistent results. Few studies examined the effects of usual dietary isoflavone intake on bone density, and none examined the effects on markers of bone turnover. This cross-sectional study examines the association of usual, unsupplemented dietary soy intake with bone density at the lumbar spine and hip and markers of bone turnover in postmenopausal women. Participants were 208 postmenopausal Southern California women aged 45-74 years. Information on behavioral and lifestyle factors was obtained, and dietary intake of isoflavones over the past year was assessed with a standardized questionnaire. Bone density was measured at the spine and hip with dual energy x-ray absorptiometry (DEXA). Urinary type I collagen cross-linked N-telopeptides (N-Tx) and pyridinium cross-links (PYR), both markers of bone resorption, and bone alkaline phosphatase (BAP), a marker of bone formation, were assayed. After adjustment for age and obesity, women with the highest daily intake of dietary genistein had N-Tx concentrations 18% lower than those of women who reported no daily genistein consumption (mean 37.29 vs. 45.44, respectively, p = 0.01). After adjustment for all covariates, there were trends toward significant differences in N-Tx (p = 0.09) and spine bone density (p = 0.07), whereby women with the highest level of isoflavone consumption had greater bone density at the spine. These results suggest that usual, unsupplemented dietary isoflavone consumption may be protective against bone loss in postmenopausal women through a reduction in bone resorption.
authors.affiliation: University of California, San Diego, School of Medicine, Department of Family and Preventive Medicine, Division of Epidemiology, La Jolla, California 92093-0631, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Kritz-Silverstein
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Goodman-Gruen
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000652:urine; D015519:Bone Density / Q000187:drug effects*; D003094:Collagen / Q000652:urine; D024042:Collagen Type I; D004032:Diet; D004311:Double-Blind Method; D005260:Female; D019833:Genistein / Q000008:administration & dosage; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage*; D008875:Middle Aged; D010012:Osteogenesis / Q000187:drug effects* / Q000502:physiology; D010455:Peptides / Q000652:urine; D017698:Postmenopause / Q000187:drug effects*; D012016:Reference Values
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D007529:Isoflavones; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; C004742:daidzein; D003094:Collagen; D019833:Genistein