Red and processed meat reduction

IARC classified processed meat as carcinogenic to humans (Group 1) and red meat as probably carcinogenic (Group 2A) in 2015, based on colorectal cancer: about 18% higher risk per 50 g/day of processed meat and 17% per 100 g/day of red meat in meta-analyses of cohorts. Absolute risk increase for an individual is a few percentage points of lifetime colorectal risk; the population-attributable fraction in high-income countries is around 5-10% of colorectal cancers. Mechanisms include N-nitroso compounds from nitrite curing, haem iron promoting endogenous nitrosation and lipid peroxidation, and heterocyclic amines from high-temperature cooking. WCRF recommends limiting red meat to about three portions (350-500 g cooked) per week and eating little if any processed meat. The 2019 NutriRECS guidelines that advised continuing current consumption drew widespread criticism for applying drug-trial evidence standards to dietary epidemiology, illustrating the recurring dispute about how much certainty diet advice needs.