Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial.
What this study found
The 120 mg/day regimen produced a modest whole-body bone benefit, but the clinical impact was limited. Adjusted whole-body BMD was significantly higher for 120 mg/day vs placebo after 1 and 2 years (sequential Sidak-adjusted P = 0.04), whereas 80 mg/day was not significant (P = 0.13). Neither dose slowed bone loss at the lumbar spine or total hip, and bone turnover markers (osteocalcin, BAP, NTx) were not favorably altered. Serious adverse events were reported in both active arms, including one breast cancer in the 120 mg/day group and one stage 1B, grade III squamous carcinoma of the…
- Study & population
- Multicenter, placebo-controlled 2-year clinical trial in healthy postmenopausal women in the United States.
- Intervention
- Healthy postmenopausal women were randomized in a 3-arm multicenter trial to oral soy hypocotyl aglycone isoflavone tablets at 80 mg/day or 120 mg/day, taken as 3 tablets daily for 24 months, versus placebo.
- Key limitation
- The benefit was small and confined to whole-body BMD, not the common fracture sites most relevant to clinical decision-making.
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Open PDFOriginal abstract
BACKGROUND Isoflavones are naturally occurring plant estrogens that are abundant in soy. Although purported to protect against bone loss, the efficacy of soy isoflavone supplementation in the prevention of osteoporosis in postmenopausal women remains controversial. OBJECTIVE Our aim was to test the effect of soy isoflavone supplementation on bone health. DESIGN A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones plus calcium and vitamin D on bone changes in 403 postmenopausal women. Study subjects were tested annually and changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and T scores were assessed. Changes in serum biochemical markers of bone metabolism were also assessed. RESULTS After study site, soy intake, and pretreatment values were controlled for, subjects receiving a daily supplement with 120 mg soy isoflavones had a statistically significant smaller reduction in whole-body BMD than did the placebo group both at 1 y (P < 0.03) and at 2 y (P < 0.05) of treatment. Smaller decreases in whole-body BMD T score were observed among this group of women at 1 y (P < 0.03) but not at 2 y of treatment. When compared with the placebo, soy isoflavone supplementation had no effect on changes in regional BMD, BMC, T scores, or biochemical markers of bone metabolism. CONCLUSION Daily supplementation with 120 mg soy hypocotyl isoflavones reduces whole-body bone loss but does not slow bone loss at common fracture sites in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.