Relation between milk-fat percentage, vitamin D, and BMI z score in early childhood.

BACKGROUND: Fortified cow milk is a material contributor of vitamin D and dietary fat in children. Recommendations for children >2 y of age advise reduced milk-fat consumption to reduce childhood obesity, yet the relation between lower milk fat, vitamin D stores, and body mass index (BMI) is unclear.

OBJECTIVES: The primary objective was to explore the association between milk-fat percentage and both BMI z score (zBMI) and venous 25-hydroxyvitamin D [25(OH)D]; the secondary objective was to assess whether milk volume consumed modified this relation.

DESIGN: This was a cross-sectional analysis. Healthy urban children aged 12-72 mo were recruited from 9 primary health care practices within The Applied Research Group for Kids (TARGet Kids!) research group in Toronto, Canada. We used adjusted bivariate linear regression to examine the relation between milk-fat percentage and child 25(OH)D and zBMI concurrently. Effect modification by milk volume consumed on the evaluated relations was explored with the use of an interaction term in the statistical model.

RESULTS: Among the 2745 included children there was a positive association between milk-fat percentage and 25(OH)D (P = 0.006) and a negative association between milk-fat percentage and zBMI (P < 0.0001). Participants who drank whole milk had a 5.4-nmol/L (95% CI: 4.32, 6.54) higher median 25(OH)D concentration and a 0.72 lower (95% CI: 0.68, 0.76) zBMI score than children who drank 1% milk. Milk volume consumed modified the effect of milk-fat percentage on 25(OH)D (P = 0.003) but not on zBMI (P = 0.77).

CONCLUSIONS: Whole milk consumption among healthy young children was associated with higher vitamin D stores and lower BMI. Longitudinal and interventional studies are needed to confirm these findings. TARGet Kids! was registered at clinicaltrials.gov as NCT01869530.