Age of cow milk introduction and growth among 3-5-year-old children

Objective: To evaluate the association between the age of cow milk introduction and childhood growth. Design: A secondary analysis of a prospective cohort study. Setting: Toronto, Canada. Participants: Healthy children z-score. Secondary outcomes were volume of cow milk consumed (cups/d) and BMI z-score. Outcomes were measured at the last visit before 5 years of age. Multiple linear regression was used to examine these relationships. Results: Among 1981 children, introduction of cow milk at a younger age was associated with greater height by 3-5 years of age (P < 0 center dot 001). Each month earlier that cow milk was introduced was associated with 0 center dot 03 higher height-for-age z-score unit (95 % CI -0 center dot 05, -0 center dot 02) or 0 center dot 1 cm (95 % CI -0 center dot 15, -0 center dot 12 cm). At 4 years of age, the height difference between a child introduced to cow milk at 9 v. 12 months was 0 center dot 4 cm (95 % CI -0 center dot 45, -0 center dot 35 cm). There was no association between the timing of cow milk introduction and volume of cow milk consumed per day or BMI z-score. Conclusions: Earlier introduction of cow milk was associated with greater height but not with weight status in children aged 3-5 years. Further research is needed to understand the casual relationship between earlier cow milk consumption and childhood height. These findings may be important for paediatricians and parents when considering when to introduce cow milk.