What are the study aims? To understand more about eating habits and age-appropriate food/drink portion sizes of children aged 6 months-5 years old, and how this affects their growth and dental health.

Why is this research important? Healthy diets in early years are important for growth and development. However, clear guidance for parents on what and how much children should eat is missing due to lack of up-to-date information.

What will the investigators do? Information will be collected at two time points. At baseline, parents/guardians of children aged 6 months-4 years from Leeds, Doncaster and East London will complete questionnaires about their child's sociodemographic information and food intake. They will be asked to record what their child eats for three separate one-day periods using an online system called 'myfood24'. Parents will also attend one in-person session for measuring their child's length/height, weight, and waist circumference.

At follow-up one year later, parents/guardians will complete surveys again, with another in-person session to look at growth and assess dental health.

What do the investigators expect to achieve and what happens next? They want to understand how growth and dental health are influenced by nutrient intakes, dietary patterns, and portion sizes for key food groups. They will also identify how much of different foods children should be eating, and whether commercial foods and sweet drinks are relevant.

They will explore which dietary factors can support healthier children; and how low intakes of key foods or vitamins/minerals in vulnerable groups could be redressed. The study will provide unique information, allowing for development of recommendations for parents and policy-makers on age-appropriate portions, on achieving good nutrition in UK children and within special dietary groups, and on dietary considerations in caring for children's teeth.

Research question

The investigators will answer questions posed by the recent Scientific Advisory Committee on Nutrition (SACN) report:

• What are age-appropriate food and drink portion sizes in relation to growth and dental health?
• What are the short-term effects (12 months) on growth and dental health of commercial foods for children; vegetarian/vegan/dairy-free dietary patterns?
• What is the impact on growth and dental health of macro- and micro-nutrient intakes; fruit juices/free sugars; formula milks for 12m+; sweeteners?

Background In the UK, little contemporary data exists on diet in young children but worrying trends in preschool overweight and dental health are reported. Current young child diets do not meet dietary recommendations and evidence-driven age-appropriate portion size recommendations are missing. Further research into the impact of plant-based diets, the use of commercial foods, and toddler milks is also recommended by SACN.

Aims and Objectives To provide new evidence on diet in children aged 6 months - 5 years, linked to optimum growth and dental health. Quantifying age-appropriate portion sizes for different foods and drinks.

• Collect data on child dietary intake, portion sizes.
• Collect data on parent and child attributes, including child anthropometrics and dental health.
• Evaluate food and nutrient intake in relation to i) growth over 12 months, ii) child and parent characteristics, including ethnic diversity, deprivation and iii) dental health.
• Make recommendations for nutrition and age-appropriate portions.

Methods 1,890 parents of young children (6 months - 4 years) will be recruited through a combination of community outreach and hospital-based recruitment. This will include participants from the Born and Bred in (BaBi) Network birth cohorts in Leeds, Doncaster, and East London, as well as from the Generation Study. Recruitment will include approximately equal distribution in each year bracket, 20% non-white, 20% from deprived locations, and 15% vegetarian/vegan/non-dairy diet. Protocols are in place to ensure recruitment targets are met. Protocols, consent forms, and questionnaires have been co-designed with our Parent Advisory Group.

Baseline data will be collected using i) online survey, ii) fieldworker-measured height/length, weight, abdominal circumference, iii) 3 x 24h measures of diet spanning several months, and may possibly include iv) saliva collection in a subsample (if funding is obtained). Follow-up data collected after 12 months will repeat baseline measures and additionally include a dental assessment.

Cross-sectional and longitudinal analysis will explore how growth and dental health are influenced by nutrient intakes, diet pattern, and food portion sizes. Age/gender appropriate portion sizes for key food groups will be characterised with linear mixed-effects modelling for specific foods/food groups in relation to the child's position on the growth chart centiles.

Anticipated Impact and Dissemination Knowledge of associations between food and nutrient intakes and growth/dental health and of suboptimal intakes in vegan/vegetarian/dairy-free or vulnerable groups will enable evidence-based guidelines on age-appropriate portion sizes and optimal diet composition.

Guideline promotion to key stakeholders and visual feedback to participants will support intake of age-appropriate portions and healthier diets. Ultimately resulting in healthier children, with better dental health. Guidelines will also highlight social inequalities, indicating specific actions to redress imbalances

Inclusion Criteria:

• Children aged 6 months-4 years along with their parents or guardians who reside in or near one of the three study locations and planned fieldwork sites: Leeds, Doncaster, or East London. For East London, eligibility includes individuals living in or near Tower Hamlets or an adjacent borough
• All participants are eligible regardless of background, language, educational ability, or literacy level.

Exclusion Criteria:

• Plan to move outside of the study area within the next 12 months
• Children not living with the consenting parent/guardian for any part of the week or not living with the consenting parent/guardian at the time of data collection (e.g. in care, hospital, or living wholly with another family member).
• Children with significant oral feeding difficulties (e.g. tube-feeding or developmental delays)
• Children that have been diagnosed with a long-term condition that affects their growth or development (e.g. hormonal or genetic conditions)
• Children from subgroups where quotas have been filled will be excluded to maintain balanced representation across all study groups (e.g., age 3, non-deprived locations).

Children aged between 6 months and 5 years living in Leeds, Doncaster and East London.

Where appropriate, de-identified datasets may be shared with external collaborators in response to reasonable, ethically approved data sharing requests. In such cases, formal data sharing agreements will be required.