Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial

By Wong et al. Am. J. Clin. Nutr. 90: 1433-9, 2009

The natural soy germ matrix in SoyLife with its typical high content of daizein was a special reason for a group of US researchers to reserch its influence on bone health. Osteoporosis Prevention Using Soy (OPUS) is a study supported by US government and designed to investigate safety and efficacy of soy isoflavones as natural alternative for prevention of osteoporosis in postmenopausal women.

On average, post menopausal women lose 4% bone mass per year. This bone loss leads to osteopenia and osteoporosis, and greatly raises the risk for bone fractures in post menopausal women. Hormone replacement therapy (HRT) used to be a treatment of choice, but increasingly alternative therapies are being sought, given the increased risk of certain cancers upon HRT use. The primary goal of the OPUS study was to determine whether isoflavones have an effect on reducing bone loss after menopause, whether they are safe during long-term use and what the optimal dosage is.

Study design

The OPUS study was a 2-year, follow-up, multicenter, randomized, double-blind, placebocontrolled, and intent-to-treat clinical trial. A group of 406 postmenopausal women in their early years of menopause were enrolled at 3 collaborating sites. Of the participants, 135 women received 80 mg/d of isoflavone therapy, 134 received 120 mg/d of isoflavone therapy, and the remaining 135 received a placebo. To account for potential differences and changes in isoflavone intakes across groups, each woman completed a Food Frequency Questionnaire (FFQ) before and after 12 & 24 months of treatment.

Bone mineral density (BMD) and bone mineral content (BMC) measurements were taken using identical DXA imaging, to asses changes in wholebody (WB), LS, TH, FN and trochanter. Scans were taken at baseline, 1yr and 2yr. In addition, blood samples were analyzed for markers of bone metabolism, and mammograms were analyzed for changes in breast density (safety).

Results

It is in the line of expectations that WB BMD and BMD T-scores decline during the study period in all study groups, due to the natural physiology in postmenopausal women. It was noted, however, that in the group taking 1 20mg/d of isoflavones, the reduction in WB BMD was significantly reduced at both year 1 and year 2 compared to placebo (Fig 1). Although these women kept experiencing loss of bone mass, the rate of loss reduced. The benefit of soy isoflavone supplementation at 120mg/d in reducing the loss of WB BMD was not reflected in BMC values at the regional sites or in the biochemical markers of bone metabolism.

 

 

Conclusion

The present OPUS study was a unique study to examine possible effects of isoflavones: 2-year duration