How healthy eating prevents cancer
Experts think that nearly 1 in 10 UK cancer cases could be prevented through healthy diets. And we know that a balanced diet can also help to maintain a healthy body weight, which can itself reduce the risk of many cancers.
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. Many of these could affect our risk of cancer.
Some foods, such as red and processed meats and salt, increase the risk of developing cancer. While others, such as fruits, vegetables and high fibre foods, can help prevent the disease.
Which cancers are affected?
The food we eat can affect our risk of developing several different types of cancer, including:
- Bowel cancer
- Stomach cancer
- Mouth cancer
- Food pipe (gullet or oesophageal) cancer
How do we know which foods lower or raise the risk of cancer?
Very few specific foods or drinks have been convincingly shown to raise or lower the risk of cancer. It is very difficult to design studies that accurately look at the effect of a single food item or nutrient.
Scientists need to conduct very large studies to see which specific foods may reduce the risk of cancer, and which could raise the risk. Many of these studies are underway, including the EPIC study (European Prospective Investigation into Cancer and Nutrition) which is part funded by Cancer Research UK. The EPIC study is the largest study into diet and cancer to date, and it involves over 500,000 people from 10 European countries who are being followed for many years. Results from EPIC and other large studies are already providing us with firmer answers.
This section will tell you about foods that are linked to cancer risk by strong scientific evidence. For more information on the research behind this information, visit the Facts and Evidence page.
How do fruit and vegetables reduce the risk of cancer?
Research suggests nearly 1 in 20 cancers in the UK may be linked to diets low in fruit and vegetables. Eating lots of fruits and vegetables has been linked to a lower risk of cancer of the mouth, oesophagus (food pipe), lung, larynx (voice box) and some types of stomach cancer.
Fruit and vegetables are an important part of a healthy diet and are an excellent source of many vitamins and minerals, as well as fibre.
Fruits and vegetables contain a wide variety of nutrients that have many different effects on the body. These nutrients include carotenoids, folate, vitamin C, vitamin E, selenium, flavonoids and various other phytochemicals (chemicals found in plants). Some of these may be linked to reduced cancer risk by doing things like:
- Mopping up harmful chemicals that could potentially damage DNA.
- Helping protect against DNA damage.
- Helping with repairing DNA.
- Blocking the formation of cancer-causing chemicals.
How does eating too much meat increase the risk of 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 the risk of cancer.
Scientists think there are a number of ways in which red and processed meat can increase the risk of cancer – they involve the chemicals found in these meats. Some chemicals are a natural part of the meat, and others are made when the meat is preserved or cooked at high temperatures.
Red and processed meat contains a red pigment called haem. Haem could irritate or damage cells in the bowel or fuel the production of harmful chemicals by bacteria in the gut, which could lead to a higher risk of cancer. Almost all red and processed meats contain greater amounts of haem than white meats. This may partly explain why red and processed meats increase cancer risk while white meats don’t.
Chemicals called nitrates and nitrites are often used to preserve processed meat. In the bowel nitrites can be converted into cancer-causing chemicals called N-nitroso compounds (NOCs). The presence of these chemicals may explain why many studies have found that processed meat increases the risk of cancer to a greater extent than red meat.
Cooking meat at high temperatures such as grilling or barbecuing can produce cancer-causing chemicals called heterocyclic amines (HCAs) and polycyclic amines (PCAs).
The presence of these chemicals may explain why some studies find that meat cooked at high temperatures might increase the risk of bowel cancer to a larger extent than meat cooked at lower temperatures, such as boiling or braising.
Visit our blog to learn more about the ways red and processed meat could increase cancer risk.
How does eating fibre cut the risk of cancer?
Much research has shown that bowel cancer is less common in people who eat lots of fibre. Fibre could help protect against bowel cancer in a number of ways.
Fibre increases the size of stools, dilutes their contents, and helps people have more frequent bowel movements. This reduces the contact time between the bowel and harmful chemicals in the stools. Fibre may also help gut bacteria produce helpful chemicals that change the conditions in the bowel. All of these things help to reduce the risk of cancer.
How does salt increase the risk of cancer?
Eating too much salt, or lots of foods high in salt, has been linked with a higher risk of stomach cancer.
Salt could increase cancer risk by damaging the stomach lining, which causes inflammation, or by making the stomach lining more sensitive to cancer-causing chemicals.
Salt could also interact with a stomach bug called Helicobacter pylori that is linked to both stomach ulcers and stomach cancer.