Age of introduction of ultra-processed foods and nutritional status in infants: evidence from a Brazilian birth cohort

To assess the age of introduction of ultra-processed foods and their association with the nutritional status of children at 12 months of age. This prospective cohort study was conducted in Botucatu, São Paulo, Brazil, with 518 children followed from birth to 12 months. The introduction of ultra-processed foods was assessed using a questionnaire applied at seven time points, through telephone interviews and home visits. Nine groups of ultra-processed foods were analyzed, considering age at introduction as the exposure variable. The outcome was BMI-for-age z-score at 12 months, calculated using the WHO Anthro software. Associations were tested using linear regression, with a significance level of p < 0.05. Infant formula was the earliest food introduced (median: 70 days), followed by cheese, yogurt, and petit-suisse (170 days). Margarine/cream cheese (300 days) and bread/savory biscuits/pizza (330 days) were introduced later. By 12 months, 97.9% of children had consumed at least one ultra-processed food, most frequently dairy products (90.9%), filled cookies/sweets (68.3%), and powdered cereals/chocolate drinks (65.3%). At 12 months, 26.1% of children were at risk of overweight, 10.8% were overweight, and 3.5% were obese. No statistically significant association was found between the age of introduction of ultra-processed foods and BMI-for-age z-score. Ultra-processed foods were introduced early and almost universally, in disagreement with official recommendations. Although no association was observed with nutritional status at 12 months, the findings highlight the need for public policies and health actions that promote breastfeeding and restrict the exposure of infants to these products.