What do we know about diet and cancer?

Welcome to our information pages on diet and its links to bowel, breast, stomach, oesophageal and mouth cancers. Follow the links to bring you to the relevant section:

Note: Links to external websites may be included on this page. The Irish Cancer Society is not responsible for the contents of external websites.

What do we know about diet and cancer in general?

It is hard to study the effects of diet on cancer because your diet includes foods that can protect you against cancer and foods that can increase your risk of cancer. The genes you inherit can also affect the way your diet influences your cancer risk.

The EPIC project (the European Prospective Investigation into Cancer and Nutrition) is the largest study of diet and health ever undertaken. The study recruited over half a million (520,000) people in ten European countries. It was designed to investigate the links between diet, cancer and other chronic diseases. A lot of what we know today about diet and cancer comes from or is confirmed by the EPIC study. Click here for more information (external link).

We don’t blame you if you feel confused by all the different messages you hear about what to eat and what not to eat. When all is said and done, the best way to protect yourself against cancer is by eating a healthy, balanced diet. Below we also outline some specific, proven ways in which our diet can affect our cancer risk.

What do we know about diet and bowel cancer?

Eating foods high in fibre can reduce the risk of bowel cancer. People who eat the most fibre have a 25-40% lower risk of bowel cancer compared to people who ate the least. Fibre protects against bowel cancer by encouraging the production of helpful chemicals and increasing the frequency of bowel movements.

Eating lots of red and processed meat increases the risk of bowel cancer. Red and processed meats contain a red pigment called haem, which is thought to encourage the production of chemicals called N-nitroso compounds, or NOCs. Many of these are known to cause cancer. Processed meat increases bowel cancer risk more than red meat.

Eating lots of fish can decrease your risk of bowel cancer. It is not clear why this is so.

What do we know about diet and breast cancer?

Eating lots of saturated fat may increase the risk of breast cancer. Fat in our diets probably affects the risk of breast cancer by increasing the levels of oestrogen and other hormones in our blood. This potentially leads to more rapid growth of breast cancers that are encouraged to grow by the hormone oestrogen.

What do we know about diet and stomach cancer?

Eating lots of fruit and vegetables may reduce the risk of stomach cancer. Fruit and vegetables are an excellent source of vitamins, minerals and fibre and have wide health benefits. Researchers are still trying to work out which specific nutrients in fruit and vegetables might reduce cancer risk.

There is growing evidence that eating lots of red and processed meat may increase your risk of stomach cancer.

There is some evidence that eating too much salty food, or food that has been preserved with salt, could increase the risk of stomach cancer. For example, stomach cancer is more common in countries like Japan where people tend to eat lots of salty and salt-preserved foods. It is thought that salt may affect the risk of stomach cancer by damaging the lining of the stomach and causing inflammation.

What do we know about diet and oesophageal cancer?

Eating five portions of fruit and vegetables a day may reduce your risk of oesophageal cancer. Fruit and vegetables are an excellent source of vitamins, minerals and fibre and have wide health benefits. Researchers are still trying to work out which specific nutrients in fruit and vegetables might reduce cancer risk.

What do we know about diet and mouth cancer?

Eating five portions of fruit and vegetables a day may reduce your risk of mouth cancer. Fruit and vegetables are an excellent source of vitamins, minerals and fibre and have wide health benefits. Researchers are still trying to work out which specific nutrients in fruit and vegetables might reduce cancer risk.

Eating a wide range of fruit and vegetables may further lower your risk of mouth cancer than eating a narrow range.

References

  • World Cancer Research Fund/American Institute for Cancer Research. Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective. Washington DC: AICR, 2007.
  • Vainio H, Bianchini F, eds. IARC Handbooks of Cancer Prevention, Vol 8: Fruit and Vegetables. Lyon, France: IARC Press, 2003.
  • Bingham SA et al. Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study. Lancet, 2003.
  • Stewart B, Kleihues P, eds. IARC, World Cancer Report. Lyon, France: IARC Press, 2003
  • Norat T et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition. Journal of the National Cancer Institute, 2005.
  • Gonzalez CA et al. Meat intake and risk of stomach and esophageal adenocarcinoma within the European Prospective Investigation Into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute, 2006.

Revised 2013, next revision 2015