Leng Huat Foo

Low Vitamin D Status Has an Adverse Influence on Bone Mass, Bone Turnover, and Muscle Strength in Chinese Adolescent Girls

Our goal in this cross-sectional study was to investigate the influence of low-vitamin D status on bone mass, bone turnover, and muscle strength in 301 healthy Chinese adolescent girls. Blood plasma 25-hydroxyvitamin D [25(OH)D] was measured by RIA and plasma and urine biomarkers of bone turnover were measured. Bone mineral content (BMC) and density and bone area for the whole body and the distal and proximal forearm were measured by dual energy X-ray absorptiometry. When vitamin D deficiency was defined as a serum 25(OH)D concentration of < or =50 nmol/L and severe deficiency as <25 nmol/L, 57.8% of subjects were vitamin D deficient and 31.2% were severely deficient. Multivariate analysis shows that girls with adequate vitamin D status had higher size-adjusted BMC for the whole body (P < 0.001), distal forearm (P < 0.001), and proximal forearm (P < 0.01) than those with poorer vitamin D status after adjusting for body size, handgrip strength, physical activity, and dietary intakes of calcium and vitamin D. Similar results were also found for handgrip muscle strength. Participants with adequate vitamin D status had significantly lower concentrations of bone alkaline phosphatase in plasma and deoxypyridinoline:creatinine ratio in urine compared with those of the vitamin D-deficient girls. Adolescent girls with adequate vitamin D status had significantly higher bone mass and muscle strength compared with those with poor vitamin D status. This may be attributed in part to a lower rate of bone remodeling with adequate vitamin D status. These findings suggest that adequate vitamin D status during adolescence is important for optimizing bone mass, which may lead to higher peak bone mass at maturity. Poor vitamin D status also compromises forearm muscle strength.

Influence of body composition, muscle strength, diet and physical activity on total body and forearm bone mass in Chinese adolescent girls

The aim of the present study was to determine association between body composition, muscle strength, diet and physical exercise with bone mineral content (BMC) and bone area (BA) in 283 Chinese adolescent girls aged 15 years in Beijing, China. Body composition, pubertal stage, physical activity and dietary intakes were assessed using standard validated protocols. Total body and forearm bone, lean body mass (LBM) and fat body mass (FBM) were determined by dual X-ray absorptiometry. Multivariate linear regression analyses were carried out to examine the predictors of BMC and BA, after controlling for potential confounders. The subjects had a mean age of 15.0 (sd 0.9) years and 99.6 % of them had reached menarche. Multivariate analyses showed that LBM, FBM, handgrip muscle strength and milk intake were significant independent determinants of BMC and BA of the total body and/or forearm sites. LBM was found to be a stronger independent determinant than FBM of BMC and BA, whereas handgrip muscle strength was only found as significant determinant of BMC and BA at the forearm sites than in total body BMC and BA. Further, total physical activity level had a significant positive association with handgrip and LBM. This suggested that greater muscle strength and higher LBM may reflect higher levels of physical activity. Therefore, continuous healthy lifestyle practices such as adequate intake of milk and continuous participation in physical activity should be encouraged throughout adolescence to optimise bone growth during this period.

Growth and Bone Mineral Accretion During Puberty in Chinese Girls: A Five-Year Longitudinal Study

There are few longitudinal data on bone development during puberty in children with low calcium intake. This 5‐yr longitudinal study showed that, in Chinese girls, the mean apparent calcium retention efficiency during puberty was 40.9%, PHV occurred at 3–0 yr before menarche, and peak bone mineral accretion occurred 1 yr later than PHV. Chinese girls have high calcium retention efficiency during puberty.

The association between dietary protein intake and bone mass accretion in pubertal girls with low calcium intakes.

To assess the association between protein intakes and bone mass accrual in girls, data were analysed for 757 pre-pubertal girls (mean age 10.1 years) in urban Beijing, China, who participated in a 5-year study including 2 years of milk supplementation (intervention groups only) and 3 years of follow-up study. At 0, 12, 24, 48 and 60 months from the baseline, bone mass of the proximal or distal forearm (PF or DF) and total body (TB) was measured with dual energy X-ray absorptiometry; dietary intakes were assessed by a 3-d food record (including two weekdays and one weekend day). Linear mixed models were used and continuous variables were logarithm transformed. The mean longitudinal Ca intake (432-675 mg/d on average) positively influenced bone mineral content (BMC) at TB, PF and DF after controlling for baseline bone mass and other possible confounders. However, negative associations were observed between protein intake (55.9-61.0 g/d on average) and BMC accrual at TB, PF or DF (beta = - 1.92, - 10.2 or - 4.82, respectively, P < 0.01) after adjustment. When protein intake was considered according to animal or plant food sources, protein from animal foods, particularly meat, had significant negative effects on BMC accrual at DF or PF after adjustment. It was concluded that higher protein intake, especially from animal foods, appeared to have a negative effect on bone mass accrual in Chinese pubertal girls with low Ca intakes.