1 School of Human Nutrition, McGill University, Sainte-Anne-de-Bellevue, Quebec, Canada.
2 Department of Medicine, Division of General Internal Medicine, McGill University, Montreal, Quebec, Canada. Electronic address: suzanne.morin@mcgill.ca.
3 Department of Medicine, Division of Clinical Epidemiology, McGill University, Montreal, Quebec, Canada.
4 Department of Health, Kinesiology and Applied Physiology, Concordia University, Montreal, Quebec, Canada; Montreal Behavioural Medicine Centre, CIUSSS-NIM, Montreal, Quebec, Canada.

Background: Adequate nutrition is important for bone health, especially for bone mineral accretion.

Objectives: The primary objective tested whether increasing dairy intake using the motivational interviewing technique (MInt) improves lumbar spine (LS) bone mineral density (BMD) after 2 y in postpubertal adolescents with habitual dairy intake of <2 dairy servings/d.

Methods: Participants (aged 14-18.9 y) were randomly allocated to: group 1 (control), group 2 (target of 3 dairy servings/d), or group 3 (target of =4 dairy servings/d) for 12 mo, with groups 2 and 3 using MInt, with an additional 12-mo nonintervention follow-up. The primary outcome was LS BMD, and secondary outcomes were: whole body, total hip (TH), and 33% distal radius BMD using DXA, bone geometry using peripheral quantitative computed tomography, and bone biomarkers.

Results: Ninety-four adolescents (16.6 ± 1.5 y) were recruited. Seventy-six (80.9%) completed the 12-mo assessments. From baseline to 12 mo, dairy intake in female groups 2 and 3 increased by 107% and 208%, respectively; and by 48% and 153% in males of groups 2 and 3, respectively. In females, group 3 had greater increases in TH BMD (4.3% to 7.5%) compared with control (3.7% to 4.9%, P = 0.04) and group 2 (0.0% to 1.7%, P = 0.04) at 12 and 24 mo. No effects due to dairy intake were observed for DXA outcomes in males for radial and tibial volumetric BMD in both sexes. None of the bone biomarkers were different among the dairy groups in females or males.

Conclusions: MInt effectively increased dairy intake with benefits to bone health only in female adolescents with previously low calcium intake who consumed =4 dairy servings/d for 12 mo. Larger studies are required to explain the lack of intervention effect in males.