Exploring the Role of Dairy Consumption on the Growth and Development of Canadian Children: Protocol for a Longitudinal Mixed Method Research.

Background: Childhood is a critical period for physical and cognitive development, in which nutrition plays a fundamental role. Dairy products, rich in calcium, vitamin D, and high-quality protein, are essential for bone health, body composition development, and cognitive performance. However, evidence on the long-term impact of dairy consumption on children's growth and development, particularly in the Canadian context, is limited. Additionally, recent revisions to the Canadian Food Guide, which classify dairy as part of the protein group rather than as a separate food group, may influence caregiver perceptions and children's dairy intake. Objective: This protocol describes a study designed to examine the longitudinal relationship between dairy consumption and key indicators of growth, bone health, and cognitive development in Canadian children aged 5 to 11 years. The secondary objective is to assess caregivers' and children's knowledge, attitudes, practices, and perceived facilitators and barriers to dairy consumption. Methods: A longitudinal convergent parallel mixed methods study is being conducted with 4 data collection points over 2.5 years (baseline, and approximately 10, 20, and 30 months). Eligible participants include children aged 5 to 11 years at baseline, residing in the Saskatoon area, with no diagnosed conditions or medication use affecting bone metabolism or cognitive development. Quantitative data include dietary intake, anthropometrics, body composition, bone density and microarchitecture, subjective and objective measures of physical activity, cognitive assessments, and a salivary biomarker. The qualitative component aims to investigate facilitators and barriers to dairy consumption through interviews with caregivers. Mixed-effects models will be applied to assess longitudinal associations, and thematic analysis will be used to analyze qualitative data. Quantitative and qualitative findings will be integrated at the interpretation stage to inform overall conclusions. Results: Ethics approval was obtained from the University of Saskatchewan Research Ethics Board (Bio-3339) in 2022. Recruitment began in September 2022 and concluded in February 2025. A convenience sample of 166 volunteer children from Saskatoon was recruited, with efforts made to achieve demographic diversity. Data collection is ongoing and expected to finish by August 2027. Data analysis is underway, with preliminary findings expected to be published in 2026. Conclusions: This protocol outlines a comprehensive study that aims to generate context-specific evidence on the role of dairy in child development, with implications for developing responsive dietary guidance and public health policy in Canada.