Objectives: While studies suggest that phytoestrogens may retard bone loss in postmenopausal women, data concerning the skeletal effects of specific phytoestrogens on adult men and premenopausal women are sparse. This study aims to examine the association between specific phytoestrogens (intake of isoflavones, coumestrol, flavonoids and lignans) and bone mineral density (BMD) at spine and femoral neck in a cohort of Southern Chinese adult men and women. We hypothesized that higher intake of specific phytoestrogens may associated with higher BMD in adult men and premenopausal women
Methods: The participants of this cross-sectional study included 957 Southern Chinese adult women and 386 men between 20 to 39 years old. Sex-specific linear regression analysis was employed to examine the association between each phytoestrogen intake (examined as continuous and categorical variable) and BMD. The models were adjusted for age, BMI, calcium intake, smoking and drinking history, number of pregnancy (for women), educational and exercise level, serum estradiol (for women and men) or testosterone (for men only) level. Analysis of covariance (ANCOVA) was used to calculate least square mean BMD by tertiles of phytoestrogen intake. A test for linear trend was conducted across sex-specific tertiles of phytoestrogens intake.
Results: Mean age was 32+/?5 years. In men, dietary lignan intake was significantly associated with lumbar spine BMD (beta = 0.093; p = 0.009) as well as femoral neck (p = 0.04). Flavonoid intake was also positively associated with lumbar spine BMD (beta = 0.075; p = 0.04), but isoflavone intake was negatively associated with lumbar spine BMD (beta = ?0.024; p = 0.01) in adult men. However, in women, similar but only marginally significant positive associations were observed for lignan intake and flavonoid intake with BMD in women (p range: 0.062?0.093). No significant associations were seen for coumestrol in men or women.
Conclusion: Specific phytoestrogens intake may be positively associated with hip and spine BMD in Southern Chinese adult men. Gender differences as well as negative association with isoflavone intake should be further investigated. This is possible that phytoestrogens are more beneficial for women after menopause when endogenous estrogen levels are low. Bioavailability of isoflavone and equol producer phenotype of subjects may affect the effect of isoflavone on bone.
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