Date of Award
2026
Keywords
Gut, microbiome, diet, fat, dairy, children, trial
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Medical and Health Sciences
First Supervisor
Therese O'Sullivan
Second Supervisor
Claus Christophersen
Third Supervisor
Amanda Devine
Fourth Supervisor
Johnny Lo
Fifth Supervisor
Mary Boyce
Abstract
Background and Objectives: Current dietary guidelines suggest children over the age of two should consume mostly reduced-fat dairy products rather than whole-fat dairy. However, there is a lack of robust data to support this, and observational research suggests whole-fat dairy could have potential health benefits. Therefore, the aim of this study was to investigate the impact of whole-fat dairy compared with reduced-fat dairy intake on children’s gut health through a double blind randomised controlled trial.
Methods: Forty-nine healthy children aged 4.00–6.99 years (mean ± SD age: 5.26 ± 0.88, girls = 21) who habitually consumed whole-fat dairy were recruited through local playgroups and early learning centres. Participants were stratified by sex and randomised to receive either whole-fat (n = 25) or reduced-fat (n = 24) dairy products for 12 weeks in a double-blind design. Assessments were conducted at baseline and end of intervention including anthropometrics, body composition and three-day weighed food records. Faecal samples and fasting blood were collected for 16S rRNA sequencing and targeted metabolomic (SCFA, TMAO and BCAA) analyses.
Results: Energy intake remained stable (baseline 6.7 ± 1.2 MJ per/day), with no significant between-group differences in body mass index or percentage body fat. Intervention compliance (³ 300 mg/day calcium) was met by all participants. Total fat intake increased significantly in the whole-fat group from 50.1 ± 2.9 g per day at baseline to 58.1 ± 3.2 g per day at the end of intervention (FDR p = 0.014), driven by higher saturated (22.0 ± 1.6 to 27.5 ± 1.6 g per day; FDR p = 0.002) and trans-fatty acid intakes (0.96 ± 0.09 to 1.45 ± 0.11 g per day; FDR p = 0.001). Energy derived from dairy was significantly higher in the whole-fat group (median 2.09 [IQR 1.81–3.07] MJ per day) compared with the reduced-fat group (1.33 [1.15–1.87] MJ per day; FDR p < 0.001), although total overall energy, protein, carbohydrate, sugars and fibre intakes did not differ between groups. At a phylum level, Firmicutes (56.4 per cent) and Bacteroidota (28.6 per cent) were dominant at baseline, and the reduced-fat group showed a significant increase in Actinobacteriota (2.77 ± 5.83 to 3.53 ± 4.57 per cent; FDR p = 0.012). At the genus level, Bacteroides increased significantly in the whole-fat group (13.5 ± 11.0 to 17.3 ± 12.3 per cent; FDR p = 0.036) and Subdoligranulum increased in the reduced-fat group (1.97 ± 2.74 to 3.71 ± 5.16 per cent; FDR p = 0.048). Baseline Shannon Diversity was 4.23 ± 0.11, and there were no significant between-group differences in a-diversity indices or b-diversity measures. Faecal SCFA, plasma TMAO and BCAA did not differ significantly between groups.
Conclusion: This research demonstrates that the paediatric gut microbiome is a resilient yet adaptable ecosystem. In children aged 4–6 years, changes in dairy-fat intake produced minor taxonomic shifts but no significant effects on microbial diversity or metabolites. Overall, these results suggest that modest variation in dairy fat is well tolerated within balanced diets and reinforce public health guidance emphasising dietary variety and plant-based foods for supporting gut and metabolic health in early childhood.
Access Note
Access to this thesis is embargoed until 25th April 2029
Recommended Citation
Deering, K. (2026). Effect of dairy fat consumption on the gut microbiome and microbial metabolites in Australian children aged 4 to 6 years: A randomised controlled trial. Edith Cowan University. https://doi.org/10.25958/15p1-xw15