Objective: Equol is more biologically active than its precursor daidzein, which is the principal isoflavone found in soybean. There are interindividual differences in the ability to produce equol; these may lead to differences in the effects of isoflavone intervention on human health. This study aimed to investigate whether the effects of soy isoflavones on bone and fat mass are related to an individual's equol status.
Design: We performed a 1-year double-blind, randomized trial to compare the effects of isoflavone (75 mg of isoflavone conjugates/day) with those of placebo on bone mineral density, fat mass, and serum isoflavone concentrations in early postmenopausal Japanese women who were classified based on their equol-producer phenotype.
Results: After 1 year, the isoflavone intervention significantly increased the serum equol concentration in the equol producers but not in the nonproducers. In the isoflavone group, the annualized changes in the bone mineral density of the total hip and intertrochanteric regions were −0.46% and −0.04%, respectively, in the equol producers and −2.28% and −2.61%, respectively, in the nonproducers; these values were significantly different (P < 0.05 for both the regions). Significant differences were observed between the equol producers and nonproducers in the isoflavone group with regard to the annualized changes in the fat mass. No significant difference in the annualized changes in bone mineral density and fat mass was observed between the equol producers and nonproducers in the placebo group.
Conclusions: Our data suggest that the preventive effects of isoflavones on bone loss and fat accumulation in early postmenopausal women depend on an individual's equol-producing capacity.
The effects of soy isoflavone intervention on preventing bone loss and fat mass accumulation in early postmenopausal Japanese women depend on an individual's equol-producing capacity.
From the 1Nutritional Epidemiology Program, National Institute of Health and Nutrition, Tokyo, Japan; 2Department of Nutrition, Tokyo Kasei University, Tokyo, Japan; 3Saga Nutraceuticals Research Institute, Otsuka Pharmaceutical Co. Ltd., Saga, Japan; 4Research and Development Department, Fujicco Co. Ltd., Kobe, Japan; 5Department of Nutritional Science, Tokyo University of Agriculture, Tokyo, Japan; and 6Regulatory and Scientific Affairs, Research Laboratory, Nisshin OilliO Group, Yokosuka, Japan.
Received November 7, 2006; revised and accepted November 30, 2006.
Funding/support: This work was supported by the Japan Health Science Foundation.
Financial disclosure: All authors have no conflicts of interest.
Address correspondence to: Yoshiko Ishimi, PhD, Nutritional Epidemiology Program, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan. E-mail: firstname.lastname@example.org.