The "pro-inflammatory imprint" of ultra-processed food exposure: a review of mechanisms affecting child and adolescent health and development via the gut microbiome-inflammation axis.

The prevalence of ultra-processed food (UPF) consumption in pediatric diets has raised significant concerns regarding long-term health. This review examines evidence for a proposed 'pro-inflammatory imprint' involving the gut microbiome-inflammation axis. Using a structured narrative synthesis of pediatric observational evidence, adult intervention studies, preclinical research, multi-omics data, and public health evaluations, we examine associations between UPF exposure and metabolic, inflammatory, cognitive, and neurodevelopmental outcomes while distinguishing direct from indirect evidence. We propose the Pediatric-Specific Integrated Dietary Inflammatory Index (cP-IDII) as an unvalidated, hypothesis-generating research framework for integrating reproducible nutrient- and processing-related dietary exposures; downstream microbial, intestinal-barrier, inflammatory, metabolic, and immune measures are reserved for external validation. Furthermore, we discuss the role of commercial determinants and environmental factors in shaping child health. The synthesis identifies measurement gaps and complementary policy entry points across product composition, food environments, affordability, and marketing. Empirical development and external validation are required before the cP-IDII can be used for clinical, epidemiological, or public health decision-making.