It is, undoubtedly, a grim – and frightening – statistic: half of us will develop cancer at some point in our lives. And despite survival prospects having leapt in recent decades, it still kills a collective 170,000 people in the UK each year.
Behind these figures is another story – of those who do not die, but live dramatically changed lives due to the after effects of the disease or the treatments that cure it. But according to Cancer Research UK, 38 per cent of cancer cases are avoidable – and for certain types, this figure is far higher.
Scientists have long warned of the harm from cigarettes, alcohol and obesity, resulting in clear public health guidance focused on cutting things out. But there has been far less clarity on the opposite question – whether it is possible to actively eat in a way that reduces your risk of developing the disease. In many cases, the answer is yes.
Dr Federica Amati, a research fellow at Imperial College London
‘There is a wealth of evidence that diet has an impact on all types of cancer,’ says Dr Federica Amati, a research fellow at Imperial College London and one of the experts behind the Zoe diet.
‘This link is because the immune system plays a crucial role in identifying and eliminating abnormal cells – and a healthy diet is key to reinforcing that system.
‘Poor metabolic health, as a result of a bad diet, and higher levels of systemic inflammation place a constant burden on the immune system. When it’s busy dealing with that, it’s less able to carry out its role in cancer detection and prevention.’
Yet despite decades of research, many people remain confused – often bombarded with conflicting advice online about what they should and should not eat. So what does the science actually say?
Why cutting out meat isn’t always better
For years, perhaps the most widely held beliefs has been that cutting out meat – particularly red meat – is one of the most effective ways to reduce cancer risk.
But one of the largest studies ever conducted on diet and cancer suggests the reality is far more complex. In the latest and most comprehensive analysis, researchers examined the diets of 1.8 million people, tracking cancer outcomes across several populations. They found that vegetarians were up to 31 per cent less likely to develop several cancers, including pancreatic, prostate, breast and kidney cancers, as well as multiple myeloma. Together, these cancers account for about a fifth of cancer deaths in the UK.
However, the same study also uncovered a striking contradiction – including for bowel cancer, the disease most closely linked to meat consumption.
Vegans had a 40 per cent higher risk of developing colorectal cancer compared with meat-eaters, while vegetarians were also more likely to develop certain cancers of the digestive tract. Vegetarians were also almost twice as likely to be diagnosed with oesophageal cancer.
Even more unexpectedly, participants who limited their intake of red meat but still ate poultry were 36 per cent more likely to develop the disease compared with those who ate red meat.
Researchers believe several factors may explain the findings. One is that meat-eaters in the study tended to consume relatively small amounts, suggesting that moderate intake may carry a very different risk profile to the high levels often associated with harm.
Another is that cutting out animal products entirely may lead to deficiencies in key nutrients.
Low calcium intake – which was most pronounced among vegans – is a known risk factor for bowel cancer.
Scientists have also pointed to compounds found in red meat, such as haem iron – a form of iron that is five times more readily absorbed by the body than plant-based iron. While its role remains debated, haem iron may support processes such as oxygen transport and cellular repair, which are essential for maintaining healthy tissues.
The findings underline a key point: when it comes to cancer risk, diet is rarely about simple rules.
Eliminating entire food groups may remove benefits as well as risks – and a moderate amount of unprocessed meat, within an otherwise healthy diet may not be harmful and could even be protective in some contexts.
The real problem is processed meat
If the evidence around fresh meat is nuanced, experts are far more united when it comes to processed meat.
Foods such as bacon, sausages and ham have been consistently linked to an increased risk of cancer – particularly of the bowel.
This is largely due to preservatives such as nitrates and nitrites, which can form carcinogenic compounds in the body.
Studies show that eating just 50g of processed meat a day – roughly two rashers of bacon – raises the risk of bowel cancer by 18 per cent. For this reason, processed meat is widely classified as carcinogenic and is one of the clearest dietary factors to limit.
The fat that protects against cancer
One of the key reasons that fish is prioritised in these diets is its high content of omega-3 fatty acids.
These are found in oily fish, such as salmon and mackerel, as well as in plant sources such as flaxseeds, walnuts and soybeans.
An analysis of diets in 195 countries in the medical journal The Lancet in 2019 found that Western European populations consume less than half the recommended amount of omega-3. The consequences may be significant.
In a 2024 study, researchers analysed data from more than 250,000 people over a decade, examining the relationship between omega-3 levels in the blood and the development of 19 different types of cancer.
Participants with higher omega-3 levels had lower rates of digestive cancers, including colon and stomach cancers, as well as lung cancer.
Researchers believe that omega-3 fatty acids work in two key ways: by reducing systemic inflammation and by influencing the gut microbiome, both of which play a central role in how effectively the immune system can detect and eliminate abnormal cells.
Fibre – the simple butpowerful defence
Despite its importance, fibre remains one of the most deficient nutrients in the UK diet. Some 96 per cent of Britons fail to meet the recommended intake of 30g a day.
Yet fibre has been linked to reduced risk of a wide range of cancers, including bowel, breast, oesophageal, prostate and ovarian cancers. For bowel cancer in particular, the relationship is striking. Studies show that for every additional 10g of fibre consumed daily, the risk falls by about 10 per cent.
Fibre exerts its effect through several biological mechanisms. When it is fermented in the gut, it produces compounds such as butyrate, which have anti-inflammatory properties and may directly inhibit cancer cell growth.
It also increases stool bulk and speeds up transit through the digestive system, reducing the time that potential carcinogens remain in contact with the gut lining.
At the same time, fibre supports the growth of beneficial gut bacteria, which are increasingly recognised as a key part of the body’s immune defence.
Wholegrain swap that can cut risk
Wholegrains are one of the most accessible ways you can increase fibre intake – yet they are still under-consumed.
Put simply, a wholegrain is a grain that has not been stripped of its natural parts. Foods such as oats, brown rice and wholemeal bread still contain the outer layer of the grain, which is rich in fibre, along with the inner parts that provide vitamins and nutrients.
By contrast, refined grains – found in white bread, pastries and many processed foods – have had these fibre-rich layers removed during processing. This not only strips out much of their nutritional value, but also means they are broken down quicker in the body, causing rapid spikes in blood sugar.
A 2020 review of several studies found that eating three portions of wholegrains a day was linked to a 17 per cent reduction in colorectal cancer risk.
Wholegrains help regulate blood sugar and fat levels, reducing the metabolic stress that can impair immune function and contribute to chronic disease. Good sources of wholegrains include oats (such as porridge or overnight oats), brown rice, wholemeal bread, wholewheat pasta, quinoa and barley.
Swapping white bread for wholemeal bread, or white rice for brown, is one of the simplest ways to improve your diet.
Fruit and vegetables: Why variety is key
When it comes to fruit and vegetables, the message from experts is increasingly focused on diversity rather than simply hitting a minimum target.
Dr Amati recommends aiming for about 30 different plant foods each week – a figure that includes fruits, vegetables, herbs, spices, nuts and seeds.
‘While this may sound like a lot, by adding a new plant into your daily routine – so having a kiwi with your lunchtime apple – it will quickly add up,’ she says.
This diversity helps to support a rich and varied gut microbiome, which plays a critical role in regulating immune responses.
Certain groups of foods appear to offer particular benefits. Cruciferous vegetables – such as broccoli, cabbage and kale – have been linked to lower risks of colorectal, lung, ovarian, bladder, kidney and prostate cancers.
A 2024 review of more than 200 studies found that higher intake of these vegetables was consistently associated with reduced cancer risk, with about five portions a week needed to see a measurable effect. Citrus fruits, including oranges, lemons, limes and grapefruits, have also been associated with a significantly lower risk of colorectal cancer – in some cases by nearly a third.
These foods are rich in compounds that help to neutralise harmful molecules, reduce inflammation and support cellular repair processes.
Ultra-processed food: A hidden risk driver
Alongside specific nutrients, the overall pattern of the diet is crucial.
Ultra-processed foods – which are often high in sugar, unhealthy fats and additives – are strongly linked to poor metabolic health.
This in turn drives chronic inflammation, a state that places ongoing strain on the immune system.
Over time, this can impair the body’s ability to detect and eliminate abnormal cells, increasing the likelihood that cancerous changes will go unchecked.
What you should be eating every day
While the science can seem complex, the practical advice is relatively simple.
Taken together, the evidence suggests that the healthiest approach is not extreme restriction, but balance.
Rather than eliminating meat entirely, many experts now favour a diet that is predominantly plant-based, but still includes moderate amounts of fish, poultry and occasional red meat.
‘The healthiest diets tend to be pescatarian diets, but with the occasional meat meal,’ says Dr Amati.
This type of diet reflects a broader pattern seen in Mediterranean-style eating, which has consistently been associated with lower rates of chronic disease, including cancer.
Here is exactly what a cancer-conscious daily diet should include:
– At least three portions of wholegrains (such as oats, brown rice or wholegrain bread)
– Five or more portions of fruit and veg, with as much variety as possible
– Regular sources of omega-3, including oily fish, flaxseeds and walnuts
– Beans, lentils and pulses to boost fibre intake
– Moderate amounts of fish and poultry, with occasional red meat
– A handful of nuts or seeds
– Minimal processed meat and ultra-processed foods
Experts say that the key to benefiting from a cancer-conscious diet is consistency – not perfection every day.
‘People do not need to be confused about what they need to eat,’ says Dr Amati. ‘As a general rule, they should follow a Mediterranean-style diet – rich in wholegrains, healthy fats and a wide range of plant foods.
‘It’s about giving your body the tools it needs to function properly – including its ability to protect you from disease.’
