Toddlerhood (ages 2-3) is a critical window when the gut microbiome is still developing and eating habits are being established. Yet, many Canadian toddlers eat diets high in sugar and salt, which may affect long-term health. This study will test whether a MED diet can improve dietary inflammation, gut health, and body composition in toddlers and whether a tailored nutrition education program for parents can help families maintain healthy eating patterns. In this study, toddlers will be randomly assigned to a 3-week MED diet or their usual diet. Families in the MED diet group will receive free meal boxes for the 3 weeks, plus guidance from a nutrition researcher through a structured education program. The standard diet group will continue their regular diet with general nutrition advice. Researchers will collect dietary information, body composition assessments, and stool samples to measure gut microbiome composition and metabolites. This first study of a controlled diet intervention in toddlers, combining behavioral support, high-quality food provision, and advanced gut microbiome analysis, will help understand how early diet shapes lifelong eating habits and health, guiding public health strategies and precision nutrition approaches to prevent chronic disease from early life.
The gut microbiome, central to immune and metabolic regulation, is highly responsive to dietary inputs. In adults, interventions like the Mediterranean (MED) diet rapidly increase beneficial microbial taxa and anti-inflammatory metabolites. Toddlerhood (24-36 months) represents a critical window when the gut microbiome continues to stabilize and dietary patterns become established. Yet, the diets of Canadian toddlers remain suboptimal, often dominated by high-sodium, high-sugar foods. The aims of this study are to determine the effects of a (i) MED diet food-provision intervention on dietary inflammation, the gut microbiome and metabolites, and body composition of toddlers aged 2-3 years at 3 weeks and (ii) comprehensive, tailored nutrition education program, with or without food provision, in promoting adherence to the prescribed diets at 3 weeks and 3 months post-baseline. This parallel randomized controlled trial at the University of New Brunswick will randomized parent-toddler dyads to either a 3-week MED diet or a Standard diet. Families in the MED diet group will receive free food provision and a tailored, theory-driven parental nutrition program. They will be provided with packaged food boxes including three meals (breakfast/lunch/dinner) and two snacks for each day of the week. Meals will be developed and prepared by a registered dietitian in UNB's metabolic kitchen under sterile conditions and delivered to parents in coolers. Families in the Standard diet group will continue to consume their regular diet and receive general nutrition education. Both groups will be initially screened using the KIDMED 2.0 to ensure they do not already adopt a MED diet. The nutrition education programs will be delivered over a 3-month period from baseline. The primary outcome is the between-group difference in Children's Dietary Inflammatory Index scores at 3 weeks, diet adherence, and program satisfaction. Secondary outcomes include microbial diversity, taxa, metabolite profiles, body composition, blood pressure, and additional feeding metrics. Assessments will occur at baseline, 3 weeks, and 3 months. Stool samples will be analyzed using shallow shotgun metagenomics and metabolomics to assess microbial taxa, SCFAs, and other metabolites. Statistical analyses, conducted in R, will include t-tests, PERMANOVA, and mediation models. The toddler years are a pivotal time for shaping lifelong eating habits and health outcomes, persisting into adolescence and adulthood. This is the first trial to test a controlled dietary intervention in toddlers, integrating behavioural theory and patient-oriented research. It will bring together a multifaceted team, combining expertise in nutrition and dietetics with cutting-edge knowledge in genomics for gut microbiome analysis. Findings will inform public health strategies and advance precision nutrition to reduce chronic disease risk from early life.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
40
A nine session nutrition and feeding program designed to assess how a Mediterranean-style diet influences toddler gut health, body composition, and inflammation. Toddlers will receive Mediterranean-style foods for the first three weeks, followed by continued guidance through bi-weekly educational sessions focused on meal preparation, food variety, and adherence. Specifically sessions will cover key topics such as toddler nutrient needs, budget-friendly meal planning, picky eating, family mealtime strategies, and mindful eating. The program emphasizes incorporating fruits, vegetables, legumes, whole grains, and healthy fats into toddler meals, reducing ultra-processed foods, and promoting balanced feeding during early childhood.
A nine session general toddler nutrition education program designed to reflect typical dietary patterns in Canadian families. Families receive sessions on topics such as feeding styles, cultural foods and feeding practices, understanding nutrition labels, food safety, choking hazards and prevention, healthy recipes, myths and misinformation, and meal structure and routines. No study foods are provided. Toddlers maintain their usual diets throughout the study while completing the same measurements as those in the intervention group.
University of New Brunswick
Fredericton, New Brunswick, Canada
Mediterranean Diet Adherence
Adherence to the Mediterranean diet will be defined as the degree to which toddlers' and parents' food intake aligns with core Mediterranean diet principles (high intake of fruits, vegetables, legumes, whole grains, fish, and healthy fats; limited red meat, processed foods, and added sugars). Adherence will be assessed using the KIDMED 2.0 questionnaire for toddlers and a validated Mediterranean Diet Adherence Screener (MEDAS) for parents, weekly for the first 3 weeks and every two weeks for the remaining 9 weeks. Scores range from 0 to 12 for toddlers and 0 to 14 for parents, with higher scores indicating greater adherence.
Time frame: Baseline, at 3 weeks, and at 3 months after enrollment.
Program Feasibility and Acceptability
Feasibility will be assessed via recruitment, retention, adherence to diet, attendance at nutrition sessions, and completion of study measures. Acceptability will be assessed through parent-reported satisfaction surveys regarding the diet and education program.
Time frame: Ongoing throughout study (baseline to 3 months).
Children's Dietary Inflammatory Index (C-DII)
The Children's Dietary Inflammatory Index (C-DII) quantifies the inflammatory potential of an individual's diet. For this study, toddler dietary intake obtained from 24-hour dietary recalls (one weekday and one weekend per week for first 3 weeks, every two weeks for final 9 weeks) will be used to calculate C-DII scores. The DII scoring algorithm assigns weights to nutrient and food component intake based on their established inflammatory properties. Higher DII scores indicate more pro-inflammatory dietary patterns, whereas lower (more negative) scores represent more anti-inflammatory diets aligned with Mediterranean-style eating.
Time frame: Baseline, at 3 weeks, and at 3 months after enrollment.
Gut Microbiome Diversity, Composition, and Metabolites
Gut microbiome diversity and taxa will be assessed using metagenomic sequencing of stool samples collected from toddlers. Alpha diversity metrics (e.g., Shannon index, Chao1) and beta diversity metrics (Bray-Curtis dissimilarity) will quantify within- and between-sample microbial diversity. Taxonomic composition at phylum, family, and genus levels will also be examined, as well as microbial metabolite profiles relevant to inflammation and metabolic regulation.
Time frame: Baseline, at 3 weeks, and at 3 months after enrollment.
Toddler Anthropometrics, Body Composition, and Blood Pressure
Toddler growth and body composition will be assessed using standardized anthropometric and air-displacement plethysmography methods. Height and weight will be measured to calculate body mass index (BMI), which will then be converted to BMI-for-age percentiles and/or z-scores using WHO growth standards to characterize growth status. Waist circumference will be collected. Body composition will be evaluated using the BOD POD Pediatric Option, an air-displacement plethysmography system that provides estimates of fat mass, fat-free mass, and percentages. Together, these metrics will provide data on dietary patterns may impact growth and body composition. Blood pressure will be measured using a manual sphygmomanometer, which will provide additional indication of cardiovascular health and risk for hypertension-related conditions.
Time frame: Baseline, at 3 weeks, and at 3 months after enrollment.
Nutrition-Related Behaviors and Feeding Practices
Parents' feeding practices and toddlers' eating behaviors will be assessed using validated self-report questionnaires, such as the Child Feeding Questionnaire (CFQ) and the Feeding Practices and Structure Questionnaire (FPSQ). Each instrument generates subscale scores by averaging item responses within each domain. For the CFQ, items are rated on 1-5 Likert scales, and subscales such as Restriction, Pressure to Eat, and Monitoring are calculated by averaging item scores; higher values indicate greater use of that feeding practice. For the FPSQ, items are also scored on Likert scales and grouped into Structure (e.g., routines, limits) and Autonomy Support (e.g., encouragement, involvement) subscales, with mean scores reflecting how frequently each practice is used. These procedures quantify parental control, responsiveness, feeding structure, and child eating behaviors (e.g., neophobia, appetite traits), offering a multidimensional profile of feeding dynamics.
Time frame: Baseline, at 3 weeks, and at 3 months after enrollment.
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