Measuring dietary components and their effect on cancer risk involves detailed, long-term study and is the focus of much research around the world. Scientists believe that our eating habits influence our risk of cancers of the bowel, stomach, mouth, pharynx (throat), oesophagus (foodpipe) and pancreas. Diet may also be a risk factor for breast, prostate, lung, cervical and bladder cancer. The story is even more complex because the effect of diet on cancer risk may be influenced by our genetic make-up. This interaction between our genes and what we eat is being researched intensively.
Healthy eating is a lifestyle choice that everyone can make and that can help reduce your risk of developing cancer. It can also prevent obesity (overweight) and protect us against heart disease, hypertension and diabetes.
Ideally, healthy eating habits should start early in life ? our diet in childhood affects our health as adults and bad habits can be difficult to change when we?re older. But it?s never too late to start eating a healthy diet. Make changes to your diet gradually, for example by introducing extra portions of vegetables to your main meal or substituting a piece of fruit for your normal dessert. And don?t worry if you can?t get fresh vegetables ? canned and frozen ones are good alternatives.
A healthy and balanced diet should
-- include plenty of fruit and vegetables
-- include foods that are high in fibre
-- include starchy foods like potatoes, pasta and rice
-- be low in fat and red and processed meat
-- Fruit and vegetables
Try to eat five portions of fruit and vegetables every day. Examples of a typical portion are
-- an orange
-- two kiwi fruit or tangerines
-- a cupful of grapes or strawberries
-- two serving spoons of broccoli or carrots
-- a bowl of salad
-- a glass of fruit juice
Beans, peas and lentils also count as portions but potatoes and nuts don?t. Follow the ?red, amber, green? rule: try to eat fruits and vegetables that are different colours, like beetroot, carrots and spinach.
Including fruit and vegetables of different colours is important because the compounds that produce the colours (pigments) may help protect against cancer. These pigments are called carotenoids. Fruit and vegetables also contain many other important things like vitamins and minerals as well as fibre and starches. Carotenoids and some vitamins are antioxidants. Antioxidants are thought to help protect our cells from damage that could potentially cause cancer.
There is evidence that eating plenty of vegetables reduces your risk of bowel cancer. A diet rich in fruit and vegetables may protect against stomach cancer and cancers of the mouth, throat (pharynx) and foodpipe (oesophagus). It may also offer protection against breast, prostate and lung cancer.
Dietary fibre is found in cereals, vegetables and fruit. It?s important for keeping the bowel working normally and may protect bowel cells from cancer-causing damage.
Fibre makes the bacteria in the gut work harder to break down food. Fibre also makes the stool more bulky which is important for moving it through the bowel. This can avoid constipation, a known risk factor for bowel cancer.
Bacteria in the gut use a process called fermentation to break down food. Fermentation is stimulated by dietary fibre. Some of the by-products of this process are thought to eliminate cells in the bowel that could start to grow abnormally.
There is also evidence that eating more fibre might reduce the risk of pancreatic cancer.
Good sources of dietary fibre include
-- bran-enriched breakfast cereals
-- wholewheat pasta and bread
-- brown rice
-- beans, peas and lentils
-- fruit and vegetables
-- Bread, cereals and potatoes
These are starchy foods and should make up a third of our diet. Starchy foods are filling and can also be a good source of fibre.
Red and processed meat
In the UK we eat a lot of red meat, including beef, pork and lamb. Red meat is a good source of protein, vitamins, minerals and iron, all important components of a healthy diet, but we should not eat too much of it. Processed meat (like sausages, burgers and pies) and cured meat (like bacon and ham) should also be eaten in moderation as their fat content is high.
Including some red meat in your diet is fine but substitute it where possible with alternative sources of protein like chicken, turkey or fish.
Eating lots of red or processed meat is a risk factor for bowel cancer. There is also some evidence that breast, lung, prostate and pancreatic cancers are linked to a diet high in red or processed meat.
The best way to incorporate more vitamins and minerals in your diet is to eat more fruit and vegetables. Tests so far have not shown that supplements are a good alternative. We don?t know for sure which components of fruit and vegetables are the most protective. And getting the full range of nutrients contained in different fruits and vegetables is probably important.
Trials suggest that supplements of b-carotene may in fact be harmful for some people. b-carotene is a precursor of vitamin A that is found mainly in red, yellow and orange fruit and vegetables. Eating fruit and vegetables like these as part of a healthy diet provides the correct dose of b-carotene needed by our cells. But tests have shown that if you are a smoker, b-carotene supplements may increase your risk of lung cancer and heart disease. The reason for this is not understood but it?s possible that high dose supplements can interfere with the natural balance of carotenoids in the body.