[Association of vitamin A with bone mineral density in middle-aged and aged females].

OBJECTIVE: To find out the vitamin A intake in middle-aged and aged females, and to investigate the relationship between retinol intake and bone mineral density (BMD). METHODS: Two hundred and fifty women aged 45 to 66 were enrolled and received physical examination and BMD scanning, and their fasting blood samples and dietary records were collected. Serum retinol and beta-carotene were analyzed by HPLC. Assays for bone turnover markers (such as bone specific alkaline phosphatase, osteocalcin and 25-(OH) D3) in serum were performed by using commercially available kits. Subjects were divided into normal BMD group and low BMD group, and the dietary RE intakes and serum retinol were compared. RESULTS: The average RE intake was 455.8 microg (n = 169), which reached 65.1% of RNI. Serum retinol and beta-carotene in normal BMD group were a little bit higher than the low BMD group, but there was no statistic difference. Vitamin A intake of normal BMD group was 53.0 microg, which was lower than the low BMD group, and carotene intake of normal BMD group was 107.6 microg, which was higher than the low BMD group. The ratio of plant sourced retinol in normal BMD group was higher than the low BMD group. Bivariate correlation analysis on BMD and dietary RE intake showed no statistic correlation, but with a slight negative trend (P = 0.203, r = -0.140). There was a significantly difference in age, bone mineral contents, BMI and BSAP between low BMD group and normal BMD group (P < 0.001 or P < 0.01), and bivariate correlation analysis showed that the age (P < 0.001, r = -0.380), BMI (P < 0.001, r = 0.394) menopausal age (P < 0.05, r = 0.244) and body weight (P < 0.001, r = 0.434) were significantly correlated with BMD. The result of stepwise linear regression analysis showed that the age, menopausal years and BSAP were entered into the regression equation (R2 = 0.552, F = 24.661, P < 0.001), which indicated a strong connection with BMD. CONCLUSION: (a) RE intake did not reach RNI, and the use of supplements was not common (32.5%). (b) The intake of milk and milk products and beans and bean products was low, and the calcium intake did not reach 50% of AI. (c) Higher serum retinol in normal range might maintain BMD. (d) Too much RE intake might associate with decreased BMD, especially the BMD in femoral bone.