Effects of school milk intervention on cortical bone accretion and indicators relevant to bone metabolism in Chinese girls aged 10–12 y in Beijing2

• Published in: The American journal of clinical nutrition 2005-05, Vol.81 (5), p.1168-1175
• Main Authors: Zhu, Kun, Du, Xueqin, Cowell, Chris T, Greenfield, Heather, Blades, Barbara, Dobbins, Timothy A, Zhang, Qian, Fraser, David R
• Format: Article
• Language: English
• Subjects: bone alkaline phosphatase; Chinese girls; cortical bone accretion; Fortified milk; insulin-like growth factor I
• ISSN: 0002-9165
• DOI: 10.1093/ajcn/81.5.1168

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.