TheSoyIsoavonesforReducing.PDFVIP

The Soy Isoflavones for Reducing Bone Loss (SIRBL) Study: a 3-y randomized controlled trial in postmenopausal women1–4 D Lee Alekel, Marta D Van Loan, Kenneth J Koehler, Laura N Hanson, Jeanne W Stewart, Kathy B Hanson, Mindy S Kurzer, and C Theodore Peterson ABSTRACT Background: Our previous study indicated that soy protein with isoflavones lessened lumbar spine bone loss in midlife women. Objective: We examined the efficacy of isoflavones (extracted from soy protein) on bone mineral density (BMD) in nonosteoporotic postmenopausal women. We hypothesized that isoflavone tablets would spare BMD, with biological (age, body weight, serum 25- hydroxyvitamin D) and lifestyle (physical activity, dietary intake) factors modulating BMD loss. Design: Our double-blind, randomized controlled trial (36 mo) in- cluded healthy postmenopausal women (aged 45.8–65.0 y) with intent-to-treat (n = 224) and compliant (n = 208) analyses. Treatment groups consisted of a placebo control group and 2 soy isoflavone groups (80 compared with 120 mg/d); women received 500 mg cal- cium and 600 IU vitamin D3. Outcomes included lumbar spine, total proximal femur, femoral neck, and whole-body BMD. Results: Analysis of variance for intent-to-treat and compliant (
80%) models, respectively, showed no treatment effect for spine (P = 0.46, P = 0.21), femur (P = 0.86, P = 0.46), neck (P = 0.17, P = 0.14), or whole-body (P = 0.86, P = 0.78) BMD. From baseline to 36 mo, BMD declined regardless of treatment. In intent-to-treat and compliant models, respectively, BMD decreases were as follows: spine (22.08%, 21.99%), femur (21.43%, 21.38%), neck (22.56%, 22.51%), and whole body (21.66%, 21.62%). Regres- sion analysis (compliant model) indicated that age, whole-body fat mass, and bone resorption were common predictors of BMD change. After adjustment for these factors, 120 mg (compared with placebo) was protective (P = 0.024) for neck BMD. We observed no treatment effect on adverse events, endometrial thickne