The link between diet and cancer is complex and difficult to unravel. This is because our diet is made up of lots of different foods and nutrients. Most of these affect our risk of cancer, often in combination with one another. The genes you inherit also affect the way diet influences your cancer risk.
Scientists need to conduct very large studies to see which specific foods protect us from cancer, and which cause it. Many of these studies are underway and their results are already providing us with firmer answers.
For now, we know about the general types of food that can help to keep us healthy. And we know that a balanced diet will help to maintain a healthy body weight, which can itself reduce the risk of many cancers.
Fruit and vegetables are likely to reduce the risk of many cancers, especially those of the digestive system, such as mouth, foodpipe and stomach cancers. However, they are unlikely to reduce the risk of cancers with hormonal causes, such as breast or prostate cancer. These foods are high in many important nutrients and are an excellent source of fibre.
Our advice: Eat at least five different portions of fruit and vegetables a day. Eating fruit and vegetables with a wide variety of colours will help you get a broad range of vitamins and minerals. Check out our 5-a-day page for more on portion sizes and tips for getting your daily portions.
Eating lots of red and processed meat can increase your risk of bowel cancer, and possibly stomach cancer. . Red meat includes all fresh, minced and frozen beef, pork and lamb. Processed meat includes ham, bacon, salami and sausages. White meat, such as chicken, is unlikely to increase your risk of cancer.
Our advice: Eat smaller and fewer portions of red and processed meat. Try substituting beans or pulses for meat in your recipes. When you do cook meat, use low-temperature methods such as braising. Cooking meat at high temperatures until it chars can produce cancer-causing chemicals.
Fish may reduce your risk of bowel cancer, although this still needs to be conclusively shown.
Our advice: Try eating more fish instead of red or processed meat. When poached, baked or steamed, it is especially good for you.
Salt-preserved or high-salt foods may increase your risk of cancers of the stomach and nasopharynx, the bit where the back of your nose meets your throat. It is unlikely that table salt used in cooking or flavouring will strongly influence your risk of cancer. But too much salt can increase your blood pressure and your risk of heart disease and stroke.
Our advice: Try not to eat too many salt-preserved or high-salt foods. And check the salt content of processed foods and ready meals. There is often salt hidden where you wouldn't expect it and you may not be able to taste it if the foods are also high in sugar.
Fibre-rich foods can reduce your risk of bowel cancer. These include fruit and vegetables, wholegrain cereals, wholemeal and wholegrain bread, brown rice and pulses.
Our advice: Boost the fibre in your diet by choosing wholegrain varieties of starchy foods wherever possible, such as wholemeal bread and wholegrain cereals. Many fruits and vegetables also contain lots of fibre, especially peas, spinach, apples, avocados, pears, berries. Other fruit and vegetables that contain moderate amounts of fibre include Brussels sprouts, green beans, broccoli, corn, spinach, carrots and oranges.
Fats are a necessary part of our diet but high-fat diets can increase our risk of cancer, heart disease and other conditions. Vegetable foods are richer in monounsaturated or polyunsaturated fats, while meat is higher in saturated fats. There is evidence that eating too much saturated fat can increase your risk of breast cancer.
Our advice: Try not to eat too many fatty foods. In particular, try to cut down on saturated fats as contained in fatty meat, biscuits, crisps, cheese and butter. Choose lean cuts of meat and semi-skimmed or skimmed milk. Try to avoid frying food in lots of oil – try steaming, braising or lightly grilling instead.
Vitamins and minerals, such as folate, selenium, calcium, and vitamins A, C and E, could reduce your risk of many cancers. It is still unclear which specific vitamins or minerals may do so. But it is likely that you need a combination of all of them.
Our advice: Eat lots of different fruit and vegetables to get a balanced complement of vitamin and minerals. Don't rely on supplements – they do not substitute for a balanced diet.