Background: Milk and dairy products play an important role in optimal growth and development of children but only 38% of New Zealand children drink at least one milk serving/day. The objectives of the study were to examine linear growth, body composition and bone mineral status of pre-pubertal children participating in the “Milk in Schools programme” over one year. The control group was recruited from schools that were not participating.

Methods: This prospective study followed 118 pre-pubertal children (5-10 years old) over one year. Body composition as well as whole body (WB) headless bone mineral content-(WB-BMC), bone mineral density (WB-BMD), lumbar spine BMC and BMD were measured with dual energy x-ray absorptiometry (Discovery A, Hologic, WI, USA). Anthropometric data including height, weight and waist circumference (WC) were collected.

Results: The total sample consisted of 42.4% males and 57.6% females, with 58 children in the control group (C’s) and 60 in the milk group (MD’s). At baseline, the MD’s were significantly older, taller and had higher WB-BMD. There were no significant differences between the groups over one year for change in height, weight, BMI z-score, WC, WB-fat and lean mass (LBM). There was a significant treatment*time interaction for WB area (p=0.046) and a marginally significant on WB-BMC (p=0.051) and BMC z-score (p=0.093), with greater increases in the MD’s. The changes in WB-BMC, WB-BMD and Z-score over one year were significantly associated with change in LBM (p<0.001). WB fat mass was significantly associated with WB-BMC (p<0.001).

Conclusions: LBM and WB fat mass significantly predicted children’s bone health. Both the control and milk groups increased in height and weight at a similar rate. The changes in WB- BMC and WB area were greater in the milk group over the year, with the BMC Z-score increasing in the milk group but remaining stable in the controls.