Long-term consumption of isoflavone-enriched foods does not affect bone mineral density, bone metabolism, or hormonal status in early postmenopausal women: a randomized, double-blind, placebo controlled study

Background: Osteoporosis is a major health problem. It was hypothesized that isoflavone-containing products may be a potential alternative to hormone replacement therapy for preventing bone loss during the menopausal transition.

Objective: The objective was to investigate whether the consumption of isoflavone-enriched foods for 1 y affects bone mineral density, bone metabolism, and hormonal status in early postmenopausal women.

Design: This was a randomized, double-blind, placebo-controlled, parallel, multicenter trial. Two hundred thirty-seven healthy early postmenopausal women [mean (+/- SD) age of 53 +/- 3 y and time since last menses of 33 +/- 15 mol consumed isoflavone-enriched foods providing a mean daily intake of 110 mg isoflavone aglycones or control products for 1 y while continuing their habitual diet and lifestyle. Outcome measures included bone mineral density of the lumbar spine and total body, markers of bone formation and bone resorption, hormones, isoflavones in plasma and urine, safety variables, and adverse events.

Results: Consumption of isoflavone-enriched products did not alter bone mineral density of the lumbar spine and total body or markers of bone formation and bone resorption. Hormone concentrations did not differ between the isoflavone and control groups. Consumption of isoflavone-enriched products resulted in increased isoflavone concentrations in plasma and urine, whereas control products did not. This finding indicated good compliance with treatment. Subgroup analysis did not support an effect of equol phenotype on bone density. The intervention had no effect on a range of safety variables and reported adverse events.

Conclusion: Consumption of foods containing 110 mg/d of soy isoflavone aglycone equivalents for 1 y did not prevent postmenopausal bone loss and did not affect bone turnover in apparently healthy early postmenopausal white women. This trial was registered at clinicaltrials.gov as NCT00301353.