Food + Cancer — What's Real
Most 'food causes cancer' headlines are overhyped
Diet + cancer science is notoriously confounded — observational studies struggle with recall bias and reverse causation, RCTs are hard to run over cancer-development timelines. But a few dietary factors have survived decades of scrutiny with real effect sizes.
Processed meat — confirmed Group 1 carcinogen
IARC classified processed meat (bacon, sausage, deli meat) as a Group 1 carcinogen in 2015 — the same category as tobacco and asbestos, not the same MAGNITUDE. About 18% increased colorectal cancer risk per 50 g/day of processed meat. Red meat sits in Group 2A (probably carcinogenic).
Ultra-processed food — the new signal
A 2018 BMJ study of 104,980 French adults found a 10% higher cancer risk per 10% increase in ultra-processed food consumption. Effect size was largest for breast cancer. This was an observational study, so confounding possible — but the pattern replicates in multiple cohorts. Don't live on UPF.
Fibre + plant diversity — protective
Higher fibre intake (25+ g/day) and plant-food diversity (30+ different plants per week) both associate with lower colorectal + breast cancer risk. Mechanism: microbiome-mediated anti-inflammation, short-chain fatty acid production, faster gut transit. The American Gut Project defined the 30-plants threshold.
Myth or Fact?
Swipe for each claim.
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Key Takeaway
The evidence-based diet for cancer prevention is the same as for cardiovascular + metabolic health: mostly plants, plenty of fibre, minimal processed + ultra-processed foods, limited alcohol, modest red meat, effectively zero processed meat. Details compound over decades.