One in twenty cancers could be prevented by eating a balanced diet, according to Cancer Research UK. But deciphering how what you eat affects your chances of developing cancer can be really confusing – it’s hard to know if the research is reliable, some foods are good in one way but bad in another, and there always seems to be a new superfood cure.
While there isn’t a ‘one size fits all’ approach to what you eat, maintaining a balanced diet and healthy weight is important for your health in general, not just when it comes to cancer. Here we share what foods have a track record for protecting against the disease – and ones that have the opposite effect.
Good news foods
Fruit and vegetables
Eating your five portions of fruit and vegetables a day isn’t just about maintaining a healthy weight: scientists have found that one in 20 cancers could be associated with eating less than your recommended daily intake.
There are two ways that fruit and veg help to protect against cancer. The first is their nutrients, such as carotenoids, folate, vitamin C, vitamin E, and selenium. These all protect against cancer in different ways. Carotenoids, for example, are antioxidants that help to stop free radical chemicals damaging cells, while folate helps to repair DNA.
The other way they protect against cancer is their fibre content. There is strong evidence to suggest that high-fibre diets are excellent ways to protect against cancer (for more details see below); eating plenty of fruit and vegetables is one way to make sure you get plenty of roughage.
But you can’t cut any corners. Each fruit and vegetable contains different – and differing amounts of – nutrients, so it's important to eat a wide variety. Supplements aren’t necessarily the answer either to boosting your intake; research suggests that when nutrients are taken as supplements, they don’t reduce your risk of cancer in the same way as when they are eaten in their natural form, and in some cases could even increase it.
Wholemeal bread, pasta and cereals, brown rice and pulses
A high-fibre diet can do wonders to protect against bowel cancer in particular, so tuck into foods such as wholegrain bread, pasta and brown rice, chickpeas, lentils, kidney beans and fruit and vegetables.
Fibre protects your bowel in a few ways. It produces a chemical (butyrate), which makes cancer less likely to develop, and speeds up the passage of food. This means potentially harmful chemicals spend less time in contact with the cells lining the bowel, and the nasty chemicals have less time to be absorbed.
The European Prospective Investigation of Cancer (EPIC) has also found that a high-fibre diet can protect against the harmful effects of eating red and processed meats in the bowel too – see below for more detail.
Eating a portion of fish (140g) a week may help protect you against bowel cancer. Some studies have also found that oily fish such as salmon, herring and mackerel may also reduce the risk of developing prostate cancer, though this hasn’t been fully substantiated yet, so it is too early to say. It’s not exactly clear why fish helps yet, more research is needed but it is an essential part of a balanced diet, provides us with essential omega-3s and is a good alternative to red and processed meat.
Not so good news
Beef, pork, lamb, bacon, ham, salami and sausages
Research shows that eating a lot of red and processed meat can increase your risk of cancer. Primarily this is in the bowel, but newer studies also show a link with pancreatic and stomach cancer too.
There are two main ways red and processed meat can increase your risk. Both contain haem, a red pigment. It is thought this could harm cells in your bowel and trigger the production of N-nitroso compounds, which are chemicals that can cause cancer. The way some processed meats are preserved can also produce these chemicals in the bowel, and cooking at high temperatures (such as grilling or barbecuing) can produce other potentially harmful chemicals.
There is some good news. Red meat contains really beneficial nutrients including protein, iron, and vitamin B12, so it is more about moderation than cutting it out, and selecting good quality produce. Aim to eat no more than about three portions of red meat a week, which is around 350–500g cooked weight (or 525–750g raw weight) a week. Also, research shows that high-fibre diets can protect you against the risks so ensuring you have plenty of roughage can help.
Keep an eye on your intake of saturated fats. Studies have shown that there is a link between saturated fat and a small increase in the chance of developing breast cancer. Although it hasn’t been properly established, it is thought that excess saturated fat in the diet increases hormones that could lead to cancer.
Research suggests that a high-salt diet – including eating salty foods and food that has been preserved in salt – increases your risk of developing stomach cancer. It’s not yet been fully established why, but it could be that salt damages the lining of the stomach or makes it more sensitive to harmful chemicals.
The recommended daily allowance is 6g per day. A simple way to eat less salt is to avoid topping meals with it and to reduce it in the cooking process. Natural salts are already in foods such as vegetables, meat and fish. If you still feel the need for extra flavour, try adding other flavourings such as herbs and spices.
Getting your salt intake right - AXA Health
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Cancer Research UK - How healthy eating prevents cancer
Gonzalez CA, Riboli E. Diet and cancer prevention: Contributions from the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Cancer. 2010;46(14):2555-2562. doi:10.1016/j.ejca.2010.07.025
Cancer Research UK - Eat healthily
NHS - Eat well