With a vegetarian diet the risk of 5 types of cancer falls: here’s which ones (and why)

For years plant-based diets have been praised for heart and climate.

Now the cancer data are getting harder to ignore.

A huge international study following more than 1.8 million people for sixteen years has mapped how different eating patterns line up with cancer risk, from heavy meat eaters to strict vegans. The findings suggest that a well-planned vegetarian diet may lower the odds of several major cancers – but the picture for vegan diets is more complicated than many might expect.

What the new research actually looked at

The analysis, led by researchers at the University of Oxford and published in the British Journal of Cancer, pooled data from large population studies in the UK, US, Taiwan and India. Participants were grouped into five broad patterns, ranging from regular meat eaters to pescatarians, vegetarians and vegans.

Everyone reported how often they ate meat, fish, dairy, eggs and plant foods. Researchers then tracked new cancer diagnoses over an average of 16 years, logging more than 220,000 cases across 17 types of cancer, including common ones like breast, prostate and colorectal, and rarer cancers such as kidney cancer, multiple myeloma and pancreatic cancer.

To avoid misleading results, the team adjusted for age, sex, BMI, smoking, alcohol, exercise and social background. They also repeated analyses after excluding the first years of follow-up, limiting the chance that early, undiagnosed disease had already changed people’s diets.

A vegetarian pattern, with no meat or fish but including dairy and eggs, was linked to a lower risk of five specific cancers: pancreas, prostate, breast, kidney and multiple myeloma.

Five cancers where vegetarians came out ahead

Compared with people who regularly ate meat, vegetarians in the study showed statistically lower risks for several major cancers. These reductions were modest rather than dramatic, but they affect diseases that kill large numbers of people every year.

• Pancreatic cancer: about 21% lower risk in vegetarians
• Prostate cancer: about 12% lower risk
• Breast cancer: about 9% lower risk
• Kidney cancer: about 28% lower risk
• Multiple myeloma (a blood cancer): about 31% lower risk

Pancreatic, breast and prostate cancers together account for roughly a fifth of cancer deaths in the UK, so even a 10–20% shift in risk can matter at population level. Men avoiding meat, and to a lesser degree those eating mainly fish, seemed to benefit most for prostate and kidney cancers.

Why might a vegetarian diet cut these risks?

Researchers point to a cluster of likely explanations rather than a single “magic” factor:

• Higher fibre intake, from whole grains, beans, fruit and vegetables, which supports gut health and influences hormones such as oestrogen and insulin.
• More antioxidants and phytochemicals, plant compounds that can help limit DNA damage and inflammation linked to cancer development.
• Less saturated fat and fewer calories from animal products, which often translates to lower body weight – a known factor in several cancers, including breast (post-menopause), kidney and blood cancers.
• Little or no red and processed meat, both tied to higher cancer rates in previous research, particularly for the digestive tract.

Vegetarians in the study tended to be leaner, eat more fibre and avoid processed meats – a trio that works in favour of cancer prevention.

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The meat question: why processed and red meat still matter

Processed meats such as bacon, ham and sausages contain added nitrites. When cooked at high temperatures, these can form nitrosamines, compounds that can damage cells in the gut lining. The World Health Organization classifies processed meat as carcinogenic, and red meat as “probably” carcinogenic, for humans.

In Italy, national estimates suggest about one in ten colorectal cancers may be linked to processed meat consumption. Similar patterns appear in other high-income countries, which is why many cancer agencies advise limiting these foods.

In the Oxford-led analysis, though, most meat eaters were not heavy processed-meat consumers. They ate on average around 17 grams of processed meat per day, roughly half the UK national average. So the comparison was between relatively health-conscious meat eaters and those avoiding meat, not between vegans and daily bacon sandwiches. Researchers argue that if bigger meat intakes had been represented, the gap in risk might have been wider.

The surprise finding: vegans and higher colon cancer risk

The most eyebrow-raising result concerned vegans. People who avoided all animal products had about a 40% higher risk of colorectal cancer than regular meat eaters in this dataset.

That runs against much previous work showing high-fibre diets as protective for the bowel. The vegan participants did report very high fibre intakes and low levels of saturated fat, both usually seen as positive for gut health.

So what is going on? Researchers are cautious. One suspicion is calcium. On average, vegans in the study consumed about 590 mg of calcium per day, below the 700 mg recommended in the UK. Calcium binds certain potentially harmful compounds in the intestine and has been associated with lower colorectal cancer risk.

The vegan diet itself may not be the problem; underdoing calcium and some key nutrients on a very strict plan could be part of the story.

Another theory involves the gut microbiome. Completely removing dairy and all animal products can reshape the bacteria living in the intestine. That shift might be beneficial in many ways, but it could also have unexpected knock-on effects on how bile acids and other chemicals are processed.

The vegan group was also the smallest, just a few thousand people across all the cohorts. That makes the risk estimate less precise and more vulnerable to quirks in the data. The authors stress that more targeted research is needed before drawing firm conclusions about vegan diets and colon cancer.

Vegetarians and oesophageal cancer: a potential red flag

The study also noted a higher risk of a specific oesophageal cancer – squamous cell carcinoma of the oesophagus – among vegetarians. The numbers of cases were low, but the relative risk was close to double.

One idea is that very restrictive diets, low in certain animal-derived nutrients, might be short on riboflavin (vitamin B2), zinc and some amino acids. These nutrients are involved in maintaining healthy mucous membranes and DNA repair. If intake is chronically low and not replaced with fortified foods or supplements, that could raise risk in sensitive tissues, including the oesophagus.

Fish, poultry and a “middle way” approach

The analysis did not just pit meat eaters against vegetarians. Pescatarians – people who eat fish but not meat – showed some advantages too. They tended to have lower risks of breast, kidney and bowel cancers. Those who mainly ate poultry rather than red meat had lower prostate cancer risk.

These patterns fit with a broader message from cancer and heart guidelines: diets that focus on plants, include fish and modest amounts of lean poultry, and go easy on processed and red meats appear consistently safer.

The label on your diet – vegan, vegetarian, flexitarian – matters less than the overall balance: plenty of plants, limited processed meat, and enough key nutrients.

How a typical day on a protective vegetarian diet might look

Translating this research into a plate of food can help. A vegetarian pattern linked with lower cancer risk could look like this:

• Breakfast: Oat porridge with berries, ground flaxseeds and low-fat yoghurt or fortified plant milk.
• Lunch: Lentil and vegetable soup, wholegrain bread, a green side salad with olive oil.
• Snack: A handful of nuts and an apple.
• Dinner: Chickpea and vegetable curry with brown rice, plus a portion of steamed greens.
• Regular extras: Dairy or calcium-fortified alternatives, eggs a few times a week, and limited highly processed meat substitutes.

That kind of pattern keeps fibre high and saturated fat relatively low, while still supplying calcium, B vitamins and protein.

Key terms that help make sense of the findings

Term	What it means in this context
Relative risk	The percentage higher or lower risk in one group versus another, not an absolute guarantee for any individual.
Cohort study	People are followed over time to see who develops a disease; diet is recorded at the start or at intervals.
Confounder	A factor like smoking or age that can distort the link between diet and cancer if not accounted for.
Processed meat	Meat preserved by smoking, curing or adding preservatives such as nitrites, for example bacon or salami.

Practical risks and benefits for anyone changing diet

For people thinking of cutting back on meat, the data support a shift towards more plants, especially whole grains, pulses, fruit and vegetables. That shift is linked not only to lower cancer risk in this study, but also to better heart health and weight control in many others.

There are pitfalls. Vegan diets that are poorly planned can miss calcium, vitamin B12, iodine, iron and omega‑3 fats. Vegetarian diets overly reliant on cheese, refined carbs and processed meat alternatives may still be high in salt and saturated fat. The protective pattern in the research reflects not just the absence of meat, but the presence of varied, nutrient-dense plant foods.

Someone moving from a typical Western diet to a thoughtful vegetarian one might, over years, nudge down their risk of several cancers while also easing the strain on their heart and kidneys. A person going straight to a restrictive vegan pattern without fortification or supplements might trim some risks but raise others, particularly if calcium and B12 are neglected.

Cancer risk never drops to zero, whatever you eat. Yet this large study strengthens the case that shifting the balance of the plate away from processed and red meat, and towards a well-rounded vegetarian pattern, can tilt the odds in a favourable direction for at least five major cancers – as long as key nutrients are not left behind.