An overview of diet and breast cancer

We may be able to prevent as many as 25 out of every 100 cancer cases (25%) by changing our diets. But it is difficult to be exact about this. Research suggests that between 15% to 35% of cancers may be preventable by changing diet. This includes cancers that could be avoided by maintaining a healthy bodyweight.

This area of research is very difficult because we all eat such a range of different foods in such differing amounts. Some people eat more fruit and vegetables than others. You could put people into two groups of mainly meat eaters and mainly vegetable and fruit eaters. But some of the fruit eaters will 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. So it is a very confusing picture to untangle.

We have a clue about diet and breast cancer when we look at the rates of the disease in Japanese and American women. Japanese women have a much lower rate of breast cancer than American women. But when Japanese women emigrate to live in the USA their breast cancer risk goes up. The risk changes. So the difference in risk must be to do with lifestyle or the environment rather than any inherited risk. The most obvious change is diet. Researchers suspect that changes in diet may be related to the change in breast cancer risk.

To draw firm conclusions about diet and disease, researchers would have to control everything a group of people ate throughout the whole of their lives. This is not really possible to do.

The next best thing is to record a large group of healthy people’s eating habits for a set period of time. And then follow them up to see who has particular illnesses later in life. This is the basis of a big Europe wide research project called EPIC (European Prospective Investigation into Cancer) which started in 1992. It is producing reports on diet and a variety of cancers over the next 10 to 20 years, starting with bowel cancer and breast cancer. If you would like to keep up to date with the findings from the EPIC study you can look on line at the EPIC website.

The research into diet causing cancer concentrates on the main groups of food that we all eat

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

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

Sugar is found in very 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 (such as cheese, milk, butter), eggs, and vegetable protein from beans, lentils, nuts, soya products (TVP, tofu).

Fruits and vegetables give us most of our fibre, vitamins and minerals. Although, of course, meat, fish and dairy foods contain some vitamins and minerals, they contain almost no fibre. There has been recent publicity about whether soya foods and other plant foods called phyto oestrogens can help prevent breast cancer. We have information about phyto oestrogens in this section of CancerHelp UK.

Other research is looking at the possible effects of being overweight or obese. There is good evidence that post menopausal women who are overweight have an increased risk of breast cancer, although in pre menopausal women being overweight reduces the risk of breast cancer. Recently, researchers have found that regularly drinking alcohol can increase breast cancer risk. There is more information about both of these on our page about definite risk factors for breast cancer.

Many people are concerned that food additives or chemicals such as pesticides can help cause cancer. But there is no consistent evidence that either of these affect cancer risk. Other factors in our diets such as coffee have also been investigated.

There is detailed information about the foods we all eat and other factors in diet in this section of CancerHelp UK.