Objective: To evaluate the effects of dietary isoflavones in soy products on menopausal symptoms, lipid profiles, and bone mineral densities in postmenopausal Japanese women.
Methods: We estimated the daily intakes of isoflavones in the diets of 478 postmenopausal Japanese women who reported soy consumption. We recorded serum values of fasting total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and apolipoproteins. Bone mineral density was measured at the lumbar spine (L2-L4) by dual energy x-ray absorptiometry. Women were assigned to two groups according to years since menopause (early and late postmenopausal groups), and each group was subcategorized into four groups according to dietary isoflavone intake. Relationships between isoflavone intake, menopausal symptoms, lipid profiles, and bone mineral density were examined in each group.
Results: The mean estimated intake of isoflavones among 478 women was 54.3 mg/day. With stepwise regression analysis we found that weight and years since menopause were significant independent predictors of bone mineral density. Bone mineral densities adjusted to years since menopause and weight were significantly different in the highest intake compared with lowest intake category (P <.001) within the early and late postmenopausal groups. In the early postmenopausal group, significant differences were found in palpitation and backaches between the high and low intake categories but were not significant in the late postmenopausal group.
Conclusion: High consumption of soy products is associated with increased bone mass in postmenopausal women and might be useful for preventing hypoestrogenic effects.