Milk intake and bone mineral acquisition in adolescent girls: randomised, controlled intervention trial

Abstract

Objectives: To investigate the effect of milk supplementation on total body bone mineral acquisition in adolescent girls.

Design: 18 month, open randomised intervention trial.

Subjects: 82 white girls aged 12.2 (SD 0.3) years, recruited from four secondary schools in Sheffield.

Intervention: 568 ml (one pint) of whole or reduced fat milk per day for 18 months.

Main outcome measures: Total body bone mineral content and bone mineral density measured by dual energy x ray absorptiometry. Outcome measures to evaluate mechanism included biochemical markers of bone turnover (osteocalcin, bone alkaline phosphatase, deoxypyridinoline, N-telopeptide of type I collagen), and hormones important to skeletal growth (parathyroid hormone, oestradiol, insulin-like growth factor I).

Results: 80 subjects completed the trial. Daily milk intake at baseline averaged 150 ml in both groups. The intervention group consumed, on average, an additional 300 ml a day throughout the trial. Compared with the control group, the intervention group had greater increases of bone mineral density (9.6% v 8.5%, P = 0.017; repeated measures analysis of variance) and bone mineral content (27.0% v 24.1%, P = 0.009). No significant differences in increments in height, weight, lean body mass, and fat mass were observed between the groups. Bone turnover was not affected by milk supplementation. Serum concentrations of insulin-like growth factor I increased in the milk group compared with the control group (35% v 25%, P = 0.02).

Conclusion: Increased milk consumption significantly enhances bone mineral acquisition in adolescent girls and could favourably modify attainment of peak bone mass.