Xueqin Du

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.

Bone mass in Chinese premenarcheal girls: the roles of body composition, calcium intake and physical activity

The association of growth and anthropometric characteristics and lifestyle factors with bone mass and second metacarpal radiogrammetry parameters was evaluated in 373 healthy Chinese premenarcheal girls aged 9-11 years. Bone mineral content (BMC) and density (BMD) and bone area (BA) of distal forearm, proximal forearm and total body, bone mineral-free lean (BMFL) mass and fat mass were measured by dual-energy X-ray absorptiometry. Metacarpal bone periosteal and medullary diameters were measured. Dietary intakes were assessed by 7 d food record and physical activity (PA) by questionnaire. BMFL and fat mass together explained 6.3 and 51.6% of the variation in total body BMC and BMD, respectively. BMFL mass contributed to a substantial proportion of the variation in forearm BMC and BMD and periosteal diameter (10.4-41.0%). The corresponding BA explained 14.8-80.4% of the variation in BMC. Other minor but significant predictors of total body bone mass were Ca intake, height, age and PA score (BMD only), and of forearm bone mass were PA score, bone age, height and fat mass. Nevertheless, after adjusting for bone and body size and for age or bone age, subjects with Ca intake above the median (417 mg/d) had 1.8% greater total body BMC (P<0.001), and subjects with PA scores above the median had 2.4-2.5% greater distal and proximal forearm BMC (P<0.05) than those below. Vitamin D intake negatively associated with medullary diameter (partial R2 1.7%). The results indicate that premenarcheal girls should be encouraged to optimise nutrition and Ca intake and exercise regularly to achieve maximum peak bone mass.

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.