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A healthy diet can reduce the risk of cancer

People with less healthy diets are more likely to develop cancer. Many studies have been conducted looking at the association between diet and cancer, and experts agree the food we eat can affect our risk of cancer 1, 2

Scientists have estimated that less healthy diets cause nearly one in ten (9%) cancer cases in the UK 3.

 

But diet is difficult to study...

Very few specific foods or drinks have been convincingly shown to increase or reduce the risk of cancer 1.This is because our diets include many different foods, and those foods consist of many different nutrients and chemicals that could affect the risk of cancer. It is very difficult to design studies that can accurately look at the effect of a single food item.

The way food intake is measured can be problematic too. Many studies use ‘food-frequency questionnaires’ which ask participants how often and how much they have eaten particular foods over a period of time. But this relies on participants accurately remembering their past food intake. Better-quality studies use ‘daily food diaries’ for participants to record what they’ve eaten each day 4, 5. But, sometimes food frequency questionnaires are the most practical approach – it’s a lot to ask people in a study to fill in a food diary every day for a long period of time.  

Also, it is very difficult to design diet studies that can accurately take account of other lifestyle factors which are very important in cancer risk, such as smoking tobacco and drinking alcohol. For example, people who drink or smoke heavily usually also have lower intake of fruit and vegetables 6. So when we see higher cancer risks in those people, it might be hard to disentangle the effects of one from the others. We need to take this possibility into account when considering the evidence on diet and cancer.

This page tells you about aspects of our diet that are linked to cancer by the current scientific evidence. Only foods which are supported by a body of good-quality evidence are included here. For the many other foods which have been studied, the current evidence is not good enough to say for definite whether there is a link.

 

Fruit and vegetables may reduce the risk of many cancers

Research has suggested that eating lots of fruit and vegetables could reduce the risk of mouth, oesophageal, bowel, throat, lung and some types of stomach cancers 1, 3, 7, 8, 9.

Some studies have found that people who eat the most fruit and vegetables can lower their risk of cancer by around 10% compared to those who eat the least 1, 10, 11. Eating one portion of fruit and/or veg each day can cut the risk of mouth cancer by half - and eating more portions cuts the risk by even more 12, 13, 14, 17.

A recent study suggested around one in 20 cancers in the UK may be linked to people eating fewer than five portions a day of fruit and vegetables 3. More than half of all mouth cancer cases, and almost half of oesophageal and laryngeal cancers, are linked to diets low in fruit and vegetables 3.

In the UK, most of us do not meet recommended levels of fruit and vegetables in the diet 15.

 

Fruits and vegetables contain nutrients that could help protect against cancer

Fruits and vegetables contain a wide variety of different nutrients with properties that could make it more difficult for cancer to develop. These nutrients include carotenoids, folate, vitamin C, vitamin E, selenium, flavonoids and various other phytochemicals (chemicals found in plants).

Some of their properties include the following 1:

  • Carotenoids act as antioxidants. Antioxidants block other chemicals known as free radicals. Free radicals are highly reactive and have the potential to cause damage to cells, including damage that may lead to cancer.
  • Folate plays a vital role in DNA repair.
  • Vitamin C and E act as antioxidants, protect DNA from damage and stimulate the immune system.
  • Small levels of selenium play an essential role as part of certain proteins which have antioxidant and anti-inflammatory properties, as well as protecting against DNA damage.
  • Flavonoids could also have antioxidant properties and reduce inflammation.

 

 

Fruit and vegetables are a good source of vitamins, minerals, and fibre

Fruit and vegetables contain a wide range of nutrients. Researchers are still trying to work out which of these might reduce cancer risk.

But it may be that you need these nutrients in balanced combinations to reduce the risk of cancer effectively 16. Differently coloured fruit and vegetables often contain different nutrients so it’s a good idea to eat a wide range of colours 17. One study found that people who eat the widest range of fruit and vegetables have 22% lower risk of mouth cancer than those who eat the narrowest range 18.  

There is strong evidence that the nutrients in fruit and vegetables do not reduce the risk of cancer when they are taken as supplements. High doses of supplements could even have harmful effects 19, 20, 21.

Fruit and vegetables are also a very good source of natural fibre, and there is strong evidence that high levels of fibre reduce risk of bowel cancer 7, 22, 23.

 

Fruit and vegetables have wide health benefits

People have been advised to increase their consumption of fruit and vegetables since the 1990s 24. Since then, many expert reports on diet and cancer prevention have supported eating five portions of fruit and vegetables a day 1, 25, 26. In 2005 the Department of Health made a concerted effort to promote their 5-a-day programme 27.

Eating plenty of fruit and vegetables can help you maintain a healthy body weight 2. Keeping a healthy weight can help you reduce the risk of bowel, breast (post menopausal), kidney, womb, oesophageal, pancreatic and gall bladder cancers 3. And getting enough fruit and vegetables can also reduce the risk of other diseases including heart disease 28. The EPIC study found that people who ate the most fruit and vegetables reduced their risk of dying from chronic diseases like heart diseases, cancer and diabetes by a quarter 29.

 

 

Eating lots of red or processed meat can increase the risk of cancer

Eating lots of red or processed meat increases the risk of bowel cancer 30, 31, 32. Red meat includes all fresh, minced and frozen beef, pork and lamb. Processed meat includes ham, bacon, salami and sausages 1.

Around a quarter of bowel cancer cases in men, and around a sixth in women, are linked to eating red or processed meat 33. Bowel cancer risk increases by more than a quarter (28%) for every 120g of red meat eaten per day, and by almost a tenth (9%) for every 30g of processed meat eaten per day 34. Processed meat is more strongly linked to cancer risk than red meat 30, 34.  

There is growing evidence that links red meat to pancreatic cancer and stomach cancer 35, 36, 37, 38, 39. The EPIC study found that eating lots of meat, particularly red and processed meat could also increase the risk of stomach cancer - people eating over 100g of meat a day had over 3 times the risk of getting stomach cancer 39. Another very large study found that people who eat the most red or processed meat have 40-50% higher risk of pancreatic cancer 40.

There is no strong evidence that eating white meat, such as chicken, can increase cancer risk 34.

In the UK, we get a fairly high proportion of our energy intake from red and processed meats 15. The Government advises that people who eat more than 90g (cooked weight) of red and processed meat a day should cut down to 70g or less 41.

There are a few different ways red or processed meat could increase the risk of cancer. The biological reasons for the link between red or processed meat and cancer are still unclear, but it is likely that chemicals found in red and processed meat play a part.
 
Red and processed meat contains chemicals that could cause cancer:

Haem


Red and processed meat contains a red pigment called haem. Haem could irritate or damage the cells in the bowel. The cells divide much more than normal to compensate for this damage. This increases the chance that one of these cells could acquire changes that set it down the road to cancer 42. There is some evidence that the effects of haem could be countered by chlorophyll, found in green vegetables 43, 44.

Haem could stimulate the bacteria in our guts to produce chemicals called N-nitroso compounds, or NOCs 45. Many of these are known to cause cancer. Almost all red and processed meats contain more haem than white meats. This may explain why red and processed meats increase bowel cancer risk while white meats do not 45.

Nitrites, nitrates and N-nitroso compounds


Nitrites and nitrates are used to preserve processed meat and may explain why some studies find that processed meat increases the risk of cancer to a greater extent than red meat 30, 46. In the bowel, nitrites are converted into N-nitroso compounds, which could cause cancer 46. One group of scientists analysed over 60 studies and found that nitrites, and foods rich in them, are linked to higher risks of stomach cancer 47.

Heterocyclic amines & polycyclic aromatic hydrocarbons


Cooking meat at high temperatures can produce harmful chemicals such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) , many of which can cause cancer 48, 49. The presence of these chemicals may explain why some studies find that meat cooked at high temperatures such as grilling or barbequing might increase the risk of bowel cancer more than meats cooked at lower temperatures such as boiling or braising 50, 51.

 

 

Eating lots of fish may lower the risk of bowel cancer

The EPIC study recently reported that people who ate an 80g portion of fish a day reduced their bowel cancer risk by a third compared to people who ate less than that in a week 52. Some other studies have shown similar results, but the evidence is still inconsistent 53.

It is not clear how eating fish could reduce the risk of cancer. Fish oils are especially rich in polyunsaturated omega-3 fatty acids (O3FAs), but there is no strong evidence that these can reduce the risk of cancer 54.

In the UK, our fish consumption is well below Government recommended levels of at least two portions of fish a week 15.

 

Eating lots of fibre can reduce the risk of bowel cancer

A recent study found more than one in ten (12%) bowel cancers are linked to a low fibre diet 3. A review of all studies on the topic has shown eating 10g of fibre per day can reduce the risk of bowel cancer by around 10% 55. Cereal fibre and whole grains seem to have the most effect on reducing bowel cancer risk 7.

In the UK, our average fibre intake is below the recommended level 15

Fibre triggers the production of helpful chemicals, and increases the frequency of bowel movements.

Bacteria in the bowel interact with fibre to produce several chemicals including butyrate.  Butyrate changes the conditions in the bowel, so that tumours are less likely to develop. Lab experiments have shown that butyrate can also stop the growth of cancer cells and cause them to die 56, 57, 58.

Fibre dilutes the contents of stools, and increases their bulk and the frequency of bowel movements 8, 9. All of this reduces the contact time between the bowel and chemicals in the stools and could reduce the amount of cancer-causing chemicals that are absorbed through the lining of the gut.

 

Eating lots of salt can increase the 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. But most evidence comes from countries with higher salt consumption than the UK, like Japan 59.  

In the UK it's thought that nearly a quarter (25%) of stomach cancer cases are linked to eating more than 6g of salt each day 3.  A review which combined the results of all relevant studies showed that people who regularly eat high amounts of salt each day have two-thirds higher risk of stomach cancer compared with those who eat low amounts 59.

Too much salt can increase blood pressure and the risk of heart disease and stroke 60.

Salt could affect the risk of stomach cancer by damaging the lining of the stomach and causing inflammation, or by making the stomach lining more sensitive to carcinogens such as nitrates. Salt could also interact with a stomach bug called Helicobacter pylori that cause both stomach ulcers and stomach cancer 61.

In the UK, we typically eat much more than the recommended 6g of salt per day 15.

 

Eating lots of saturated fat may increase the risk of breast cancer

Most studies on fat intake and the risk of breast cancer have suggested either no link or a small increased risk of the disease. Most studies that have found a small increased risk of breast cancer showed links with the intake of total fat or saturated fat 62, 63, 64. An analysis of four UK studies found no association between fat intake and breast cancer risk in middle-aged women 65.

Altogether, it is still not clear whether fat intake affects the risk of breast cancer. But if there is an effect, it is probably because fat in our diets increases the levels of oestrogen and other hormones in our blood, which fuels the development of cancer 66.

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References

  1. World Cancer Research Fund/American Institute for Cancer Research, Food, nutrition, physical activity and the prevention of cancer: a global perspective. 2007, Washington DC: AICR.

  2. Boyle P. et al. European Code Against Cancer and scientific justification: third version (2003). Ann Oncol. 2003 Jul;14(7):973-1005.
  3. Parkin, M., et al., The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. BJC 2011. 105, Supp. 2, 6 December 2011.
  4. Bingham SA et al. Validation of dietary assessment methods in the UK arm of EPIC using weighed records, and 24-hour urinary nitrogen and potassium and serum vitamin C and carotenoids as biomarkers. Int J Epidemiol 1997;26(suppl 1):S137–51
  5. Bingham S et al. Associations between dietary methods and biomarkers, and between fruits and vegetables and risk of ischaemic heart disease, in the EPIC Norfolk Cohort Study. Int J Epidemiol 2008;37:978–87.
  6. Serdula MK, Byers T, Mokdad AH, Simoes E, Mendlein JM, Coates RJ (1996) The association between fruit and vegetable intake and chronic disease risk factors. Epidemiology 7(2): 161–165 PubMed
  7. Boeing, H., et al., Intake of fruits and vegetables and risk of cancer of the upper aero-digestive tract: the prospective EPIC-study. Cancer Causes Control, 2006. 17(7): p. 957-69
  8. Miller, A.B., et al., Fruits and vegetables and lung cancer: Findings from the European prospective investigation into cancer and nutrition. Int J Cancer, 2004. 108(2): p. 269-276.
  9. Gonzalez, C.A., et al., Fruit and vegetable intake and the risk of stomach and oesophagus adenocarcinoma in the European Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST). Int J Cancer, 2006. 118(10): p. 2559-66.

  10. Benetou, V., et al., Vegetables and fruits in relation to cancer risk: evidence from the Greek EPIC cohort study. Cancer Epidemiol Biomarkers Prev, 2008. 17(2): p. 387-92. PubMed
  11. Freedman, N.D., et al., Fruit and vegetable intake and head and neck cancer risk in a large United States prospective cohort study. Int J Cancer, 2008. 122(10): p. 2330-6. PubMed
  12. Pavia, M., et al., Association between fruit and vegetable consumption and oral cancer: a meta-analysis of observational studies. Am J Clin Nutr, 2006. 83(5): p. 1126-34. PubMed
  13. Linseisen, J., et al., Fruit and vegetable consumption and lung cancer risk: updated information from the European Prospective Investigation into Cancer and Nutrition (EPIC). Int J Cancer, 2007. 121(5): p. 1103-14. PubMed
  14. Riboli, E. and Norat,T., Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. Am J Clin Nutr, 2003. 78(3 Suppl): p. 559S-569S. PubMed

  15. National Diet and Nutrition Survey http://www.natcen.ac.uk/our-research/research/national-diet-and-nutrition-survey-(ndns)/ 
  16. Ohigashi, H., A. Murakami, and Cancer prevention with food factors: Alone and in combination. Biofactors, 2004. 22: p. 49-55. PubMed

  17. IARC, World Cancer Report, ed. B. Stewart and P. Kleihues. 2003, Lyon. IARC Press.

  18. Garavello, W., et al., Diet diversity and the risk of oral and pharyngeal cancer. Eur J Nutr, 2008. PubMed

  19. Hercberg, S., S. Czernichow, and P. Galan, Antioxidant vitamins and minerals in prevention of cancers: lessons from the SU.VI.MAX study. Br J Nutr, 2006. 96 Suppl 1: p. S28-30. PubMed

  20. Martínez ME et al. Dietary supplements and cancer prevention: balancing potential benefits against proven harms. J Natl Cancer Inst. 2012 ;104(10):732-9. PubMed

  21. Mayne ST et al. Lessons learned from randomized clinical trials of micronutrient supplementation for cancer prevention. Annu Rev Nutr. 2012 Aug 21;32:369-90. PubMed

  22. Bingham, S.A., 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. 361(9368): p. 1496-501. PubMed

  23. British Nutrition Foundation http://www.nutrition.org.uk/nutritionscience/nutrients/dietary-fibre?start=2 (accessed June 2014)

  24. Department of Health (1998). Nutritional Aspects of the Development of Cancer. Report of the Working Group on Diet and Cancer. Committee on Medical Aspects of Food Nutrition Policy. HMSO: UK

  25. IARC, Fruits and Vegetables. IARC Handbooks of Cancer Prevention, ed. H. Vainio and F. Bianchini. Vol. 8. 2003, Lyon: IARC

  26. Diet, nutrition and the prevention of chronic diseases. Report of the joint WHO/FAO expert consultation. WHO Technical Report Series, No. 916 (TRS 916) 2003.

  27. Department of Health (2005). Choosing a Better Diet: A Food and Health Action Plan.

  28. He FJ et al. Increased consumption of fruit and vegetables is related to a reduced risk of coronary heart disease: meta-analysis of cohort studies. J Hum Hypertens. 2007 Sep;21(9):717-28.

  29. Agudo, A., et al., Fruit and vegetable intakes, dietary antioxidant nutrients, and total mortality in Spanish adults: findings from the Spanish cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Spain). Am J Clin Nutr, 2007. 85(6): p. 1634-42. PubMed
  30. Chan DS et al. Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PLoS One. 2011;6(6):e20456.

  31. Norat, T., et al., Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition. J Natl Cancer Inst, 2005. 97(12): p. 906-16. PubMed

  32. Larsson, S.C. and A. Wolk, Meat consumption and risk of colorectal cancer: A meta-analysis of prospective studies. Int J Cancer, 2006. PubMed

  33. Parkin DM (2011e). Cancers attributable to dietary factors in the UK in 2010. II Meat consumption. Br J Cancer105 (S2):S24-S26. Link

  34. Norat, T., et al., Meat consumption and colorectal cancer risk: dose-response meta-analysis of epidemiological studies. Int J Cancer, 2002. 98: p. 241-56. PubMed

  35. Larsson SC, Wolk A. Red and processed meat consumption and risk of pancreatic cancer: meta-analysis of prospective studies. Br J Cancer. 2012 Jan 31;106(3):603-7.
  36. Larsson SC, Håkanson N, Permert J, Wolk A. Meat, fish, poultry and egg consumption in relation to risk of pancreatic cancer: a prospective study. Int J Cancer. 2006 Jun 1;118 (11):2866-70. PubMed

  37. Larsson, S.C., L. Bergkvist, and A. Wolk, Processed meat consumption, dietary nitrosamines and stomach cancer risk in a cohort of Swedish women. Int J Cancer, 2006. PubMed

  38. Gonzalez, C.A., et al., Meat intake and risk of stomach and esophageal adenocarcinoma within the European Prospective Investigation Into Cancer and Nutrition (EPIC). J Natl Cancer Inst, 2006. 98(5): p. 345-54. PubMed

  39. Song P et al. Red meat consumption and stomach cancer risk: a meta-analysis. J Cancer Res Clin Oncol. 2014 Jun;140(6):979-92

  40. Stolzenberg-Solomon, R.Z., et al., Meat and meat-mutagen intake and pancreatic cancer risk in the NIH-AARP cohort. Cancer Epidemiol Biomarkers Prev, 2007. 16(12): p. 2664-75. PubMed

  41. Scientific Advisory Committee on Nutrition. Iron and Health. London: TSO, 2010
  42. Cross, A.J., J.R. Pollock, and S.A. Bingham, Haem, not protein or inorganic iron, is responsible for endogenous intestinal N-nitrosation arising from red meat. Cancer Res, 2003. 63(10): p. 2358-60. PubMed

  43. Bingham, S., et al., Does increased endogenous formation of N-nitroso compounds in the human colon explain the association between red meat and colon cancer? Carcinogenesis, 1996. 17: p. 515-523. PubMed

  44. Balder, H.F., et al., Heme and chlorophyll intake and risk of colorectal cancer in the Netherlands cohort study. Cancer Epidemiol Biomarkers Prev, 2006. 15(4): p. 717-25. PubMed

  45. Navarro, A., et al., Meat cooking habits and risk of colorectal cancer in Cordoba, Argentina. Nutrition, 2004. 20: p. 873-877. PubMed

  46. Larsson SC, Wolk A. Red and processed meat consumption and risk of pancreatic cancer: meta-analysis of prospective studies. Br J Cancer. 2012 Jan 31;106(3):603-7.

  47. Jakszyn, P. and C.A. Gonzalez, Nitrosamine and related food intake and gastric and oesophageal cancer risk: A systematic review of the epidemiological evidence. World J Gastroenterol, 2006. 12(27): p. 4296-4303. PubMed

  48. Layton, D., et al., Cancer risk of heterocyclic amines in cooked foods: an analysis and implications for research. Carcinogenesis, 1995. 16: p. 39-52. PubMed

  49. Gooderham, N., et al., Assessing human risk to heterocyclic amines. Mutat Res, 1997. 376: p. 53-60. PubMed

  50. Sinha, R., et al., Meat, meat cooking methods and preservation, and risk for colorectal adenoma. Cancer Res, 2005. 65(17): p. 8034-41. PubMed

  51. Cross AJ, Ferrucci LM, Risch A, et al. A large prospective study of meat consumption and colorectal cancer risk: An investigation of potential mechanisms underlying this association. Cancer Research 2010; 70(6):2406–2414

  52. Hall, M.N., et al., A 22-year Prospective Study of Fish, n-3 Fatty Acid Intake, and Colorectal Cancer Risk in Men. Cancer Epidemiol Biomarkers Prev, 2008. 17(5): p. 1136-43. PubMed

  53. Wu S et al. Fish consumption and colorectal cancer risk in humans: a systematic review and meta-analysis. Am J Med. 2012 Jun;125(6):551-9

  54. MacLean, C.H., et al., Effects of omega-3 fatty acids on cancer risk: a systematic review. JAMA, 2006. 295(4): p. 403-15. PubMed

  55. Aune D et al. Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies. BMJ. 2011;343:d6617.

  56. Lipkin M, Reddy B, Newmark H, Lamprecht SA. Dietary factors in human colorectal cancer. Annu Rev Nutr1999;19:545-86

  57. Bingham SA. Mechanisms and experimental and epidemiological evidence relating dietary fibre (non-starch polysaccharides) and starch to protection against large bowel cancer. Proc Nutr Soc. 1990 Jul;49(2):153-71.

  58. Boffa LC et al. Modulation of colonic epithelial cell proliferation, histone acetylation, and luminal short chain fatty acids by variation of dietary fiber (wheat bran) in rats. Cancer Res.1992 Nov 1;52(21):5906-12

  59. D'Elia L et al. Habitual salt intake and risk of gastric cancer: a meta-analysis of prospective studies. Clin Nutr. 2012 Aug;31(4):489-98.

  60. MacGregor GA. Nutrition and blood pressure. Nutr Metab cardiovasc Dis 9: 6-15 1999.

  61. Shikata, K., et al., A prospective study of dietary salt intake and gastric cancer incidence in a defined Japanese population: the Hisayama study. Int J Cancer, 2006. 119(1): p. 196-201. PubMed

  62. Thiébaut AC et al. Dietary fat and postmenopausal invasive breast cancer in the National Institutes of Health-AARP Diet and Health Study cohort. J Natl Cancer Inst. 2007 Mar 21;99(6):451-62.

  63. Freedman LS et al. A comparison of two dietary instruments for evaluating the fat-breast cancer relationship. Int J Epidemiol. 2006 Aug;35(4):1011-21.

  64. Sieri S et al. Dietary fat and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition. Am J Clin Nutr. 2008 Nov;88(5):1304-12

  65. Key TJ et al. Dietary fat and breast cancer: comparison of results from food diaries and food-frequency questionnaires in the UK Dietary Cohort Consortium. Am J Clin Nutr. 2011 Oct;94(4):1043-52.
  66. Wu, A.H., M.C. Pike, and D.O. Stram, Meta-analysis: dietary fat intake, serum estrogen levels, and the risk of breast cancer. J Natl Cancer Inst, 1999. 91(6): p. 529-34. PubMed
Updated: 15 September 2014