Effects of school milk intervention on cortical bone accretion and indicators relevant to bone metabolism in Chinese girls aged 10-12 y in Beijing.
Zhu K, Du X, Cowell CT, Greenfield H, Blades B, Dobbins TA, Zhang Q, Fraser DR.
Faculty of Veterinary Science and the School of Public Health, University of Sydney, Sydney, NSW, Australia. kathyz@vetsci.usyd.edu.au
BACKGROUND: We previously reported that increased milk consumption enhances growth and bone mineral accretion in Chinese girls aged 10-12 y. OBJECTIVE: Our objective was to evaluate the effects of milk supplementation on cortical bone accretion and to study the physiologic mechanisms underlying the observed changes in bone. DESIGN: Chinese girls aged 10 y were randomly assigned into calcium-fortified milk (Ca milk), calcium and vitamin D-fortified milk (CaD milk), and control groups according to their schools in a 24-mo school milk intervention trial. Periosteal and medullary diameters of metacarpal bone were measured at baseline and 24 mo in the Ca milk (n = 177), CaD milk (n = 210), and control (n = 219) groups. Insulin-like growth factor I (IGF-I), parathyroid hormone (PTH), bone alkaline phosphatase (BAP), osteocalcin, and deoxypyridinoline concentrations were measured at baseline and at 12 and 24 mo in the Ca milk (n = 43), CaD milk (n = 44), and control (n = 41) groups. RESULTS: After adjustment for pubertal status and clustering by school, 24-mo supplementation led to greater increases in periosteal diameter (1.2%) and cortical thickness (5.7%) and to smaller gains in medullary diameter (6.7%) than did the control (P < 0.05). The CaD milk group had lower serum BAP at 12 mo (19.9%) and lower serum PTH at 12 (46.2%) and 24 (16.4%) mo than did the control group (P < 0.05). The effect of milk supplementation on increasing IGF-I concentrations at 24 mo (16.7-23.3%) was significant in individual analyses but not after adjustment for clustering by school. CONCLUSIONS: Milk supplementation showed positive effects on periosteal and endosteal apposition of cortical bone.
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PMID: 15883444 [PubMed - indexed for MEDLINE]