Investigating cardiometabolic health and child-centred research in young children participating in The Milky Way Study: A randomised controlled dairy intervention

Background There is limited evidence to support the common public health guideline that children over 2 years should consume mostly reduced-fat dairy. Recruitment can be an issue in paediatric research, potentially due to confronting child assessments, and there is a growing international momentum to develop respectful research and healthcare protocols for children. Aims The primary aim of this thesis was to investigate the effects of whole-fat compared with reduced-fat dairy intake on measures of adiposity and cardiometabolic risk factors in healthy 4 to 6-year-old children. Secondary aims were to investigate: 1) differential changes in erythrocyte fatty acids (FAs) with changes in dairy fat consumption, and 2) to develop and test a child-centred approach in a paediatric clinical trial. Methods The Milky Way Study enrolled 49 children (mean ± SD age: 5.2 ± 0.9 years; 47% girls) who were habitual consumers of whole-fat dairy, then randomly assigned them in a double-blind fashion to remain on whole-fat dairy or change to reduced-fat products for 3 months. Primary endpoints included measures of adiposity, body composition, blood pressure, fasting serum lipids, blood glucose, glycated haemoglobin (HbA1c), and C-reactive protein (CRP); together with weighed 3-day food records and erythrocyte fatty acids, these were assessed at baseline and study end. Pre- and post-intervention results were compared using SPSS (version 28) linear mixed models, adjusted for growth, age, and sex. The Milky Way Study Respectful Approach to Child-centred Healthcare (ReACH) incorporated findings from pre-trial community consultation with parents. It was evaluated across all study clinics using mixed methods, with evaluation triangulated from 3 stakeholder perspectives. Results Dairy fat intake was significantly decreased in the reduced-fat compared with the whole-fat dairy group (p = 0.003), confirmed by significant changes in erythrocyte pentadecanoic acid, whereas dietary energy intakes remained similar (p = 0.936). We found no significant adjusted differential changes between dairy groups in any measure of adiposity, body composition, blood pressure, or fasting serum lipids, glucose, HbA1c, and CRP. Adjusted mixed models showed significant differential reductions over 3 months in the reduced-fat compared with the whole-fat dairy group for erythrocyte saturated fatty acids myristic acid (p = 0.043) and pentadecanoic acid (p \u3c 0.001), but also for omega-3 fatty acids, EPA (p \u3c 0.001) and DPA (p = 0.004). Children achieved high compliance rates for assessments, and adherence to study ReACH principles during clinic visits was positively associated with child compliance. Parents rated the Milky Way Study very highly, and qualitative feedback reflected an enjoyable study experience for parents and children. Conclusions Results do not support the guideline that reduced-fat dairy products are preferable over whole-fat for young children. Dairy fat intake can significantly impact erythrocyte fatty acid composition in young children. Adherence to the ReACH approach was associated with high child compliance rates and high participant satisfaction with the study