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What we know about diet and bowel cancer

Men and women discussing bowel cancer

This page tells you about how diet may affect your risk of bowel cancer. You can find the following information

 

A quick guide to what's on this page

What we know about diet and bowel cancer

Researchers think that more than 4 out of 10 cancers (40%) could be prevented by lifestyle changes, such as eating a healthy balanced diet and keeping active. Diet is a difficult area of research because we all eat such a range of different foods in such different amounts.

No single diet can guarantee you won't get bowel cancer. But changing your diet could help to reduce your risk of cancer in general, as well as improving your overall health.

If you have been diagnosed with bowel cancer, your dietary needs may be different because of your illness or treatment. If you have bowel cancer and are concerned about your diet, ask your doctor to refer you to a dietician.

 

CR PDF Icon You can view and print the quick guides for all the pages in the about bowel cancer section.

 

 

Can diet cause cancer?

Researchers think that many bowel cancers may be prevented with changes in diet and lifestyle. A Cancer Research UK review of the research so far looking at all cancers suggests that about 1 in 10 cancers are linked to an unhealthy diet. This means that by eating a healthy diet you can lower your risk of developing cancer.

 

What research can tell us

One reason this area of research is so difficult is that we all eat such a range of different foods in such different amounts. Some people eat more fruit and vegetables than others. You could put people into 2 groups of mainly meat eaters and mainly vegetable and fruit eaters. But say some of the fruit eaters love chocolate. So do some of the meat eaters. Some of the meat eaters eat only natural and organically raised foods. But some of the vegetarians eat a lot of crisps and processed foods. It is a very confusing picture to untangle.

To find out more about diet and disease, researchers have been recording a large group of healthy people's eating habits for some years. They are following them to see who becomes ill later in life, and what illnesses they get. This Europe wide research project is called the European Prospective Investigation into Cancer (EPIC). It started in 1992 and has produced some reports about bowel cancer. It will produce more over the next 10 to 15 years.

So far, the EPIC study has found that a high fibre diet reduces the risk of bowel polyps and bowel cancer. In 2011, a large analysis of lots of studies (a meta analysis) also found that a high intake of dietary fibre, particularly cereal and whole grains, reduces bowel cancer risk. 

We know that eating red and processed meat increases bowel cancer risk. Eating 100 to 120 grams of red meat per day can increase risk by up to a third (30%).  100 grams is about 4 ounces or 1/4 of a pound. For processed meat, studies do show an increase in bowel cancer risk but the degree of risk varies between the studies.  Overall, they show an increase in risk of between 10% and 50% for people eating between 25 and 50 grams a day.  50 grams is about the same as one sausage or 2 rashers of bacon.

Other factors interact with dietary factors to increase bowel cancer risk including drinking alcohol, being very overweight (obese), and taking little or no exercise.

 

Research into diet and cancer

Research into diet and causes of cancer concentrates on the main groups of foods that we all eat

  • Fats
  • Sugars and starchy carbohydrates
  • Proteins
  • Fruit and vegetables

Fats include oils, butter and margarine as well as fat in meat, fish and nuts. Remember there are hidden fats in sweets, cakes, biscuits and other ready made foods.

Sugar is found in many ready prepared foods and we often don't know it's there. Starchy carbohydrates include rice, potatoes, pasta and all types of bread.

Protein comes from meat, fish, dairy products (cheese, milk, butter), eggs, beans, lentils and nuts.

Fruit and vegetables give us most of our fibre, vitamins and minerals. A diet rich in fruit and vegetables may lower bowel cancer risk. But the evidence is not conclusive. Fibre, particularly from cereals and wholegrains, seems to lower the bowel cancer risk. Meat, fish and dairy foods contain some vitamins and minerals, but almost no fibre.

Some research has found that being overweight or obese increases colon cancer risk. And people who do little physical activity also have a higher risk of bowel cancer.

Many people are concerned that food additives or chemicals such as pesticides cause cancer. Other chemicals that we take in may be harmful, such as alcohol. There is more detail about diet on the pages about foods we all eat and other factors.

 

Trying to prevent bowel cancer

No single diet can guarantee you won't get bowel cancer. But changing your diet could help to reduce your risk of cancer in general as well as improving your overall health. Research is beginning to link bowel cancer to different dietary factors. In the rest of this section we have tried to include what is known about using diet to help prevent bowel cancer. We also discuss current theories or concerns that are unproved.

If you have bowel cancer your dietary needs may be different because of your illness or treatment. So the information in this section may not be right for you. If you are concerned about your diet, ask your doctor or specialist nurse to refer you to a dietician.

Bowel cancer lifestyle choice impact statement

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Updated: 26 September 2013