Does red and processed meat cause cancer?

The objection

“Nutrition headlines flip every year, and ‘carcinogen’ gets thrown around loosely. The meat studies are observational and built on food questionnaires, and the people who eat the most bacon also tend to smoke more, drink more and exercise less, so a rise of 18% is small enough for those differences to explain. In 2019 a panel that went through the same evidence told adults to carry on eating meat as they do, and humans have eaten meat forever.”

The answer

The scientists who assessed the evidence knew it was observational, and weighed it accordingly. In October 2015 the International Agency for Research on Cancer (IARC), the World Health Organization’s cancer agency, brought together 22 experts from 10 countries, who considered more than 800 studies and gave the most weight to large prospective cohort studies [1]. They classified processed meat as carcinogenic to humans (Group 1), on sufficient evidence that it causes bowel (colorectal) cancer, and red meat as probably carcinogenic (Group 2A), on limited evidence in people backed by strong evidence of how it could cause cancer [1][3]. It also saw links between red meat and cancers of the pancreas and prostate, and between processed meat and stomach cancer, though for these the evidence fell short of showing cause [3][4]. The working group’s summary appeared in The Lancet Oncology (Bouvard et al., 2015) [2]. Limited evidence means a link was seen but chance, bias or confounding could not be ruled out, which for red meat was because several of the larger studies found no association [3][4]. For processed meat the working group judged that the amount of data, the strength of the link and its consistency across cohorts in different populations, including most of the larger ones, made those explanations unlikely [3].

The size of the effect comes from meta-analyses that pool the cohorts. The one IARC quoted (Chan et al., 2011) found bowel cancer risk about 18% higher for every 50 g of processed meat eaten a day, a relative risk of 1.18 (95% CI 1.10 to 1.28), and 17% higher for every 100 g of red meat, 1.17 (1.05 to 1.31), a figure IARC said would apply only if the red meat link proves causal [3][4][5]. The World Cancer Research Fund’s review of cohort studies, published in 2017 and revised in 2018, came out close, at 1.16 (1.08 to 1.26) per 50 g of processed meat across 10 studies and 1.12 (1.00 to 1.25) per 100 g of red meat across eight, a red meat result it reported as not statistically significant [6]. Its expert panel still judged processed meat a convincing cause of bowel cancer and red meat a probable one [6].

Those are relative risks, and bowel cancer starts from a baseline of a few percent: Cancer Research UK puts the lifetime risk at 1 in 20 for women and 1 in 17 for men born in the UK in 1961 [7]. In UK Biobank, which followed 474,996 adults for an average of 6.9 years, each extra 70 g a day of red and processed meat came with a 32% higher rate of bowel cancer (hazard ratio 1.32, 95% CI 1.14 to 1.53; Knuppel et al., 2020) [8]. Cancer Research UK translated that study into numbers of people in 2024: of every 10,000 participants eating under 11 g a day, 45 were diagnosed with bowel cancer, and eating 79 g a day, similar to the UK average, meant 14 extra cases per 10,000, after allowing for smoking, alcohol, physical activity, body mass index and other differences between the groups [9]. IARC’s head of monographs, Kurt Straif, made the same point in 2015, that the risk to an individual remains small but rises with the amount eaten, while the number of people who eat processed meat makes its effect on cancer a matter of public health [1]. Citing a 2018 analysis of UK cancers, Cancer Research UK estimates that about 13% of the UK’s bowel cancers are caused by eating processed meat [7].

The strongest case against came in 2019, when the NutriRECS panel suggested that adults carry on eating unprocessed red meat and processed meat at their current levels, a weak recommendation on low-certainty evidence that also weighed people’s own values and preferences about eating meat (Johnston et al., 2019) [10]. Its review of cohort studies pointed the same way as IARC, with less confidence: cutting processed meat by three servings a week went with very small falls in cancer deaths over a lifetime and in bowel cancer, on evidence it rated low to very low certainty because of residual confounding and recall bias in how diets were measured (Han et al., 2019) [11]. A 2022 Burden of Proof study rated the evidence linking unprocessed red meat to bowel cancer as weak, two stars out of five, though even its most cautious estimate, averaged over intakes from 0 to 98 g a day, was a risk at least 6% higher than eating none (Lescinsky et al., 2022) [12]. A 2025 Burden of Proof analysis of processed meat also gave its link with bowel cancer two stars, reflecting weak relationships or inconsistent evidence, but its most cautious estimate still put the risk at least 7% higher, on average, for intakes of about 1 to 55 g a day than for none, and its authors concluded that limiting processed meat should still be recommended (Haile et al., 2025) [20]. The dispute is over how certain the harm is, how large it is, and whether a small risk to each person justifies advice to everyone. The World Cancer Research Fund, Cancer Research UK and the NHS all advise limiting red and processed meat [13][14][15], the WHO is writing a guideline of its own [16], and IARC’s director noted in 2015 that red meat also has nutritional value [1].

Is processed meat as bad as smoking?

Processed meat causes far fewer cancer deaths than smoking, even though IARC puts both in Group 1. IARC’s 2015 questions and answers explain that its groups describe how strong the evidence is that something causes cancer and do not assess the level of risk, so sharing a group with tobacco smoking and asbestos does not make processed meat equally dangerous [4]. The Global Burden of Disease estimates it quoted at the time put about 34,000 cancer deaths a year worldwide down to diets high in processed meat, and 50,000 to diets high in red meat if that link proves causal, against about 1 million from tobacco smoking, 600,000 from alcohol and more than 200,000 from air pollution [4]. What the shared group does say is how certain the processed meat link is: Cancer Research UK says it is as sure of it as it is of other proven causes such as tobacco and alcohol [14].

Why does processed meat cause cancer?

No single ingredient explains it, and IARC found strong evidence that several components of meat act together [3]. Nitrites and nitrates, added to cure meat and keep it fresh for longer, can become N-nitroso compounds in the gut, which can damage the cells lining the bowel, and Cancer Research UK suggests these added preservatives may be why processed meat raises the risk more than red meat does [14]. Haem, the red, iron-containing pigment found mostly in red meat, also drives the formation of N-nitroso compounds and fat oxidation products in the gut, and in experiments calcium suppressed some of its effects, such as the rise in fat oxidation products [3][9][14]. Cooking meat at high temperatures or over a flame, as in grilling, pan-frying and barbecuing, forms heterocyclic aromatic amines and polycyclic aromatic hydrocarbons, which damage DNA [3][14]. IARC added that there were not enough data to say whether the way meat is cooked changes the cancer risk, and that how red and processed meat raise it is not yet fully understood [4].

What counts as processed and red meat?

Red meat is the muscle meat of any mammal, including beef, veal, pork, lamb, mutton, horse and goat, and processed meat is any meat that has been salted, cured, fermented, smoked or otherwise treated to add flavour or make it keep [4]. IARC’s examples of processed meat include ham, sausages, hot dogs, corned beef, biltong and jerky, canned meat and meat-based sauces, and it notes that processed meats can contain poultry or offal as well as pork and beef [4]. The NHS also counts pâtés and sliced luncheon meats made from chicken and turkey [15], while the World Cancer Research Fund says fresh sausages and other minced meats sometimes count as processed and sometimes do not [13]. IARC did not evaluate poultry or fish [4], and Cancer Research UK says white meat and fresh, tinned or frozen fish are not linked to a higher risk of cancer [14]. IARC’s definitions cover meat only, so they say nothing either way about plant-based sausages and burgers, which the answer on plant-based meat and ultra-processing looks at.

How much red meat is too much?

The NHS says that anyone eating more than 90 g of red and processed meat a day, cooked weight, should cut down to 70 g [15]. Cancer Research UK says 70 g is about three slices of sandwich ham [17], and the NHS’s portion weights put a slice of ham at 23 g, a portion of Sunday roast at 90 g and a cooked breakfast of two sausages and two thin rashers of bacon at 130 g [15]. The cancer charities set a weekly limit for red meat and ask for even less processed meat: the World Cancer Research Fund advises no more than about three portions of red meat a week, about 350 to 500 g cooked, and very little, if any, processed meat, because no level of processed meat has been linked to an absence of bowel cancer risk [13], and Cancer Research UK suggests the same three portions and as little processed meat as possible [14]. Tim Key, who co-led the UK Biobank analysis, said its results suggest that eating a bit less than the 70 g guideline gives a slightly lower risk [9]. Whether very small amounts carry any risk is still argued over. A 2024 reanalysis that looked only at people eating less than the US median found no link with bowel cancer at 20 g of processed meat a day (relative risk 1.01, 0.87 to 1.18), although with all intakes included it did find one at 20 g (1.07, 1.02 to 1.12), and its authors concluded that a no-risk limit of zero is inconsistent with the evidence (Pouzou and Zagmutt, 2024) [23]. That work was part-funded by Matprat [23], which describes itself as Norway’s information office for eggs and meat, working on behalf of Norwegian farmers [24]. The 2025 Burden of Proof analysis still found extra risk at intakes of about 1 to 55 g a day [20]. IARC’s evaluation could not establish whether any level is safe [4], and the WHO says it is now writing a guideline on how much animal-source food, red and processed meat included, people should eat [16].

Advice (year)	Red meat	Processed meat
NHS (2024)	Over 90 g a day of red and processed meat together: cut to 70 g	Counted in the same 70 g
World Cancer Research Fund (2025)	No more than about 3 portions a week, about 350 to 500 g cooked	Very little, if any
Cancer Research UK (2025)	No more than 3 portions a week	As little as possible
WHO (2026)	Guideline being written	Guideline being written
US Dietary Guidelines (2025-2030)	Listed among the animal protein foods to eat a variety of, with no amount given	Not named
NutriRECS panel (2019)	Carry on as now	Carry on as now

The NutriRECS advice is a weak recommendation based on low-certainty evidence [10], and the NHS figure is a cooked weight [15]. The US guidelines are the only government advice here that sets no limit on red meat: they ask people to “consume a variety of protein foods from animal sources, including eggs, poultry, seafood, and red meat”, and instead of naming processed meat as the UK bodies do, they ask for meat with “no or limited added sugars, refined carbohydrates or starches, or chemical additives” [25].

Does cutting out meat prevent bowel cancer?

Cutting out meat removes one known cause of bowel cancer, but the people who have done it show that this alone does not prevent the disease. IARC did not directly compare vegetarians with meat-eaters in 2015, because the two groups can differ in other ways besides eating meat [4]; two 2026 analyses have since made that comparison, and the same caveat applies to them. In a pooled analysis of nine cohorts and 1.8 million people followed for a median of 16 years, pescatarians had a 15% lower risk of bowel cancer than meat-eaters (hazard ratio 0.85, 95% CI 0.77 to 0.93), vegetarians showed no clear difference (1.03, 0.94 to 1.13) and vegans had a 40% higher risk (1.40, 1.12 to 1.75) (Dunneram et al., 2026) [21]. Its authors said the vegan result rests on only 93 cases and was no longer statistically significant once the first four years of follow-up were left out, though it held in people who had never smoked, and that it does not fit the fall in risk expected from eating no meat [21]. The vegans in those cohorts drank the least alcohol and ate the most wholegrains and fibre, but they also had the lowest calcium intakes, a median of 590 mg a day against the UK adult reference of 700 mg [21]. Citing the World Cancer Research Fund’s judgement that dairy products and calcium supplements probably protect against bowel cancer, the authors suggest low calcium may explain the result [21]. A 2026 meta-analysis of prospective studies found a 14% lower risk in vegetarians than in non-vegetarians (relative risk 0.86, 0.76 to 0.97, six studies) and no clear difference in vegans (1.02, 0.71 to 1.48, three studies), with body mass index explaining a moderate part of the differences it found (Aune et al., 2026) [22].

Eating less processed meat lowers one risk among several, and eating less red meat probably does too [14], but neither is a substitute for screening or for seeing a GP about symptoms. Citing a 2018 analysis of UK cancers, Cancer Research UK links about 28% of the UK’s bowel cancers to eating too little fibre, 11% to overweight and obesity, 7% to smoking and 6% to alcohol [17]. It suggests swapping some red meat for pulses such as chickpeas, beans or lentils [14], and choosing wholegrain bread, rice and pasta for more fibre [17].

See a GP if you have symptoms such as blood in your poo or bleeding from your bottom, changes in your poo or in how often you go that are not usual for you, tummy pain or a lump in your tummy, or weight loss without trying [18]. In England, people aged 50 to 74 who are registered with a GP are posted a home test kit every 2 years, and people aged 75 or over can ask for one by calling the screening helpline on 0800 707 6060 [19]; elsewhere in the UK and beyond, ask your doctor about bowel screening. IARC said the data did not allow conclusions about people who have already had cancer, so if you have had bowel cancer, ask your cancer team before changing how you eat [4]. Eating less red meat also means finding its nutrients elsewhere, and Cancer Research UK points to pulses, green leafy vegetables, nuts and seeds for iron, and to fortified cereals, breads and dairy alternatives for vitamin B12 [14]. If you also cut out dairy, plan for enough calcium, which was lowest in vegans in the 2026 pooled analysis [21].