Soy isoflavones attenuate bone loss in early postmenopausal Chinese women - A single-blind randomized, placebo-controlled trial

Background: Previous studies show that daily doses of 40-99 mg soy isoflavones produce inconsistent effects on preventing estrogen-related bone loss in postmenopausal women. Aim of study: To examined the bone-sparing effect of isoflavones at a higher dose in early Chinese postmenopausal women. Methods: A total of 90 eligible women aged 45-60 years were randomly assigned to three treatment groups (30 subjects/group) with daily dosages of 0 (placebo), 84 and 126 mg isoflavones for 6 months. Further inclusion criteria included body mass index < 30 kg/m(2) and Kuppermann Climacteric Scale > 15. Bone mineral density (BMD) of the spine and hip were measured using dual- energy X-ray absorptiometry at 0 and 6 months. Serum osteocalcin, bone-specific alkaline phosphatase (BAP) and urinary deoxypyridinoline were examined at 0, 3 and 6 months. Results: Mean percent changes in BMD at the lumbar spine (p = 0.114) and femoral neck (p = 0.053) increased with the supplementations of soy isoflavones after adjusting for age, years since menopause, body weight and height, dietary intakes of isoflavones, calcium and protein, physical activities and baseline BMD at the relevant sites. We observed significantly dose-dependent linear relationship between the supplemental isoflavones and percent changes of BMD at the spine (p = 0.042) and femoral neck (p = 0.016) post-treatment, and urinary total deoxypyridinoline (p = 0.014) at 12 weeks but not at 24 weeks after adjusting for the above factors. No significant difference in percent changes in serum osteocalcin (p > 0.05) and BAP (p > 0.05) was found among the three treatment groups at 12-week and 24-week post-treatment. Conclusions: There is a significantly dose-dependent effect of soy isoflavones on attenuating bone loss at the spine and femoral neck possibly via the inhibition of bone resorption in non-obese postmenopausal Chinese women with high Kuppermann Scale.