| Soy phytoestrogens are naturally occurring compounds that contain isoflavones, which have estrogenic properties and can bind to estrogen receptors in bone tissue. As a result of these properties, isoflavones are being examined as alternatives to conventional hormone replacement therapy (HRT). The goal of this randomized placebo-controlled crossover trial was to investigate the effect of isoflavone supplementation (110 mg/d) on bone mass and markers of bone turnover in healthy postmenopausal women for 6 months. Nineteen women were recruited to participate in the study. Subjects were excluded if they had been on HRT in the previous 3 months, were within 8 years past menopause, had a history of bone, kidney, endocrine, or liver disease, or used medications that affect bone. Serum samples were assayed for osteocalcin and bone specific alkaline phosphatase (BSAP). Urine samples were assayed for type 1 collagen α1 chain helical peptide (HP). Lumbar spine and hip bone mineral content (BMC) and density (BMD) were measured via DEXA. The mean age of the study population was 70.6 ± 6.3 years, and the mean years since menopause was 19.1 ± 5.5 years. There was a significant difference in HP levels when treatment (43.43 ± 22.81 μg/mmol cr) was compared to control (56.29 ± 31.50 μg/mmol cr) (p < 0.05), and HP concentrations decreased by 37% during the treatment phase to premenopausal levels. Serum osteocalcin decreased during the treatment phase compared to pre-treatment for both crossover groups (p < 0.05), and serum BSAP levels were lower for the treatment (23.91 ± 7.13 U/L) compared to the control (24.94 ± 6.55 U/L) but not significantly lower. There was a 3.5% increase in lumbar spine BMC and 1% increase in lumbar spine BMD after treatment. Total hip BMC and BUD increased by 3.6% and 1.3%, respectively. These data suggest that isoflavone supplementation favorably altered postmenopausal bone turnover rates by significantly decreasing bone resorption, modestly decreasing the rate of bone formation, and thus the net effect is on increased bone mass. |
