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.
Parent is ≥19 years of age.
Carried a singleton pregnancy.
Delivered at term (≥37 weeks gestation).
Delivered vaginally or by cesarean section.
Toddler has food allergies or dietary restrictions (e.g., gluten-free) that make it difficult to follow a Mediterranean diet.
Toddler is at high risk for food allergies (e.g., strong family history of multiple food allergies common to the Mediterranean diet).
Toddler is already following a Mediterranean diet.
Toddler has had recent or active consumption of antibiotics, probiotics, or prebiotic drops.
Parallel
Mediterranean Diet Nutrition Program
BehavioralA 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.
Standard Diet Education Program
BehavioralA 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.
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.
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.
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.
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.
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.
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.
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