Ultra-processed Foods, Cancer, and Early-onset Cancer: A Comprehensive Review

The classification of foods according to their degree of processing, and particularly the concept of ultra-processed foods, is relatively new. Consumption of ultra-processed foods has increased markedly worldwide in recent decades. Their growing consumption has coincided with a rising global burden of cancer, including marked increases in several cancers diagnosed before age 50 years. In this comprehensive review, we summarize trends in ultra-processed food consumption and the sociodemographic, psychological, and behavioral characteristics associated with higher intake. We further review the epidemiological evidence linking ultra-processed foods with cancer incidence and mortality, with particular attention to the limited but emerging evidence relevant to early-onset cancer. Potential mechanisms linking ultra-processed foods to cancer include unfavorable nutrient displacement, changes in body composition and fat deposition, and increased exposure to additives, processing by-products, and other chemicals. These influences may converge on a range of biological pathways, including metabolic dysfunction, chronic inflammation, immune dysregulation, gut microbiome disruption, DNA damage and genomic instability, and epigenetic alterations. Substantial uncertainties remain, including heterogeneous exposure definitions and classification practices, limitations in dietary assessment and temporal exposure capture, residual confounding, and the complexity of putative biological mechanisms. We conclude by highlighting key research challenges and future directions, along with considerations related to policy, regulation, and industry practices.