Red meat causes cancer

What we know

In October 2015, the International Agency for Research on Cancer (IARC), part of the WHO, evaluated more than 800 epidemiological studies on the relationship between red and processed meat consumption and cancer risk. IARC classified processed meat, meaning meat that has been transformed through salting, curing, fermentation, or smoking such as bacon, sausages, and deli meats, as a Group 1 carcinogen, meaning there is sufficient evidence it causes cancer in humans, specifically colorectal cancer. Red meat, meaning unprocessed mammalian muscle meat such as beef, pork, and lamb, was classified as Group 2A, "probably carcinogenic to humans," reflecting strong but not fully conclusive evidence, based primarily on a positive association with colorectal cancer found consistently across many epidemiological studies along with mechanistic evidence.

It is important to understand that IARC's classification system evaluates the strength and consistency of evidence that a substance causes cancer under some circumstance of exposure, not the overall magnitude of an individual's personal risk increase. Group 1 also includes tobacco smoking and asbestos, but this does not mean processed meat carries a comparable absolute risk to smoking; rather it means the evidence that an effect exists at all is similarly strong and consistent, while the size of that effect differs enormously between these different exposures. The WHO's accompanying analysis estimated that consuming 50 grams of processed meat daily, roughly two slices of bacon, is associated with an approximately 18 percent increased relative risk of colorectal cancer, a real but comparatively modest effect size relative to the roughly 15 to 30-fold increased lung cancer risk associated with regular smoking.

The proposed biological mechanisms behind this association include the formation of N-nitroso compounds and polycyclic aromatic hydrocarbons during meat processing, curing, and high-temperature cooking methods such as grilling or pan-frying, along with the heme iron naturally present in red meat, which can promote the formation of these compounds in the digestive tract. These mechanisms provide biological plausibility supporting the epidemiological associations found in large cohort studies such as the EPIC study across multiple European countries and various long-running US cohort studies.

The World Cancer Research Fund and American Institute for Cancer Research, drawing on this evidence base, recommend limiting red meat consumption to no more than about 350 to 500 grams of cooked weight per week and minimizing processed meat consumption, rather than eliminating red meat entirely, framing this as a risk-reduction guideline rather than an absolute prohibition. Some more recent nutritional science commentary, including a controversial and widely debated 2019 set of publications in the Annals of Internal Medicine, has argued that the certainty of harm from moderate red meat consumption is lower than commonly portrayed and that individuals should weigh the modest risk against personal dietary preference; this reanalysis was itself criticized by many nutrition researchers for methodological choices that may have understated the strength of the underlying association, illustrating that reasonable scientific debate continues about the precise magnitude of risk even though the basic direction of the epidemiological association is not seriously disputed. Cooking method also plays a measurable role independent of the meat category itself: charring or blackening meat at very high temperatures increases the formation of heterocyclic amines and polycyclic aromatic hydrocarbons regardless of whether the meat is red, white, or processed, meaning that preparation technique is itself a modifiable risk factor that consumers can adjust separately from the broader decision of how much red or processed meat to include in their diet.

Common claims

• Eating any red meat causes cancerOverstated. Risk is dose-dependent; classification reflects evidence strength, not risk size
• Processed meat like bacon and sausage increases colorectal cancer riskSupported, IARC Group 1 classification based on consistent epidemiological evidence
• The WHO says red meat is as dangerous as smokingFalse, same evidence-strength category does not mean same magnitude of risk

Evidence hierarchy

All sources

• IARC Monographs evaluate consumption of red meat and processed meatInternational Agency for Research on Cancer · 2015
• Q&A on the carcinogenicity of red meat and processed meatWorld Health Organization · 2015
• Limit red and processed meatWorld Cancer Research Fund · 2023
• Red and Processed Meat and Cancer RiskAmerican Institute for Cancer Research · 2023

Related terms