Food types and bowel cancer
This page tells you about the foods in our daily diets and how they may affect the risk of bowel cancer. You can find the following information
Food types and bowel cancer
- Fibre – we know from research that fibre (particularly cereals and whole grains) is likely to protect against bowel cancer
- Fruit and vegetables – the large European Prospective Investigation into Cancer and Nutrition (EPIC) study has shown that people who eat a lot of fruit and vegetables may have a lower bowel cancer risk
- Meat – eating a lot of red meat, particularly processed meat, increases bowel cancer risk
- Fish – eating more fish may lower your risk of bowel cancer
- Calcium and vitamin D – high intakes of calcium and vitamin D may lower the risk of bowel cancer
- Dairy - milk is probably protective against bowel cancer
People who are overweight or obese have an increased risk of bowel cancer. Being physically active reduces the risk.
Alcohol and smoking also increase bowel cancer risk.
You can view and print the quick guides for all the pages in the about bowel cancer section.
Fibre is found mostly in fruit, vegetables and cereals, including flour and bread. The World Cancer Research Fund (WCRF) classifies dietary fibre as probably protective against bowel cancer. About 12 out of 100 bowel cancers (12%) in the UK are linked to eating less than 23 grams of fibre a day.
Fibre is recommended as part of a healthy diet. It can help to prevent other chronic diseases such as heart disease and diabetes. It is not clear whether the protective effect against bowel cancer is due to fibre itself or to other protective properties of fruit, vegetables and cereals. Another possible explanation is that people who eat a high fibre diet also tend to have less food in their diets that increase the risk, such as red and processed meat.
There are a couple of theories to explain the protective effect of fibre in your diet
- You need fibre to help waste products travel through the bowel
- Some types of fibre help to carry bile acids that could potentially cause cancer through the bowel more quickly
People who do not eat enough fibre tend to be constipated. So any cancer causing agents are in contact with the bowel lining for longer and increase bowel cancer risk.
Eating more fruit and vegetables may lower the risk of bowel cancer, according to results from the European Prospective Investigation into Cancer and Nutrition (EPIC) study. But the evidence is not conclusive. The WCRF has classified non starchy vegetables and fruit as possibly protective against bowel cancer, based on limited evidence.
A meta analysis in 2011 found that increasing fruit or vegetable intake from very low levels up to about 100 to 200 grams a day reduced bowel cancer risk by around 10%. But there was no further reduction in risk with higher amounts of fruit and vegetables.
Fruit and vegetables may be protective because they contain vitamins and minerals. Researchers think that antioxidant vitamins and minerals help prevent cell damage that may lead to cells becoming cancerous.
Fruit and vegetables may also be protective because of their fibre content. Diets higher in fruit and vegetables tend to be lower in meat and fat. We do not really know whether it is the fibre or the antioxidant vitamins that make the most difference.
If you take vitamin supplements instead of eating more fruit and vegetables, you miss out on the fibre and on other substances in plant foods that may help prevent cancers, such as flavonoids and carotenoids.
The WCRF say that garlic probably protects against bowel cancer. But more studies are needed.
The WCRF say that red and processed meats increase bowel cancer risk. It is estimated that around 1 in 5 bowel cancers in the UK are linked to eating these meats. Red meat includes lamb, pork, veal and beef. Processed meat includes sausages, salami, ham, bacon, paté and tinned meat.
Poultry meats, such as chicken and turkey, probably don't increase your risk of bowel cancer.
There is mixed evidence around whether eating fish is protective against bowel cancer. The WCRF thinks there is limited evidence on this link. Fish might protect against bowel cancer because some types contain fats called long chain polyunsaturated fatty acids.
Cooking methods may increase the cancer risk of meat and fish. Meats cooked at very high temperatures can form chemicals that are thought to increase cancer risk. But studies have not linked these chemicals specifically to bowel cancer.
In some studies, high fat diets have been linked to bowel cancer. But many researchers think this may be tied up with meat intake. Other researchers think that it is not fat that causes the problem, but an unhealthy lifestyle in general. A 2011 meta analysis showed no link between dietary fat intake and bowel cancer.
Calcium is probably protective against bowel cancer, according to the WCRF.
A 2004 meta analysis showed that people with the highest levels of calcium intake (from food and supplements) reduced their risk of bowel cancer by 22% compared to people with the lowest calcium intake. However 2 meta analyses in 2010 found that calcium supplements had no effect on bowel cancer risk in the general population. But they did find a link between calcium intake and a reduced risk of polyps coming back in the bowel after previous treatment. Polyps are growths in the bowel that may develop into cancer over a long period of time, if left untreated.
To reduce bowel cancer risk, it may be better to take vitamin D and calcium together. We need vitamin D to be able to absorb calcium. A large randomised controlled trial in 2006 showed that only the people with high intakes of both calcium and vitamin D had a reduced risk of bowel cancer. Other studies have shown that people with the highest intakes of vitamin D have a lower risk of bowel cancer and bowel polyps. Currently the WCRF classifies vitamin D as possibly protective against bowel cancer.
The WCRF classifies milk as probably protective against bowel cancer.
A review in 2011 showed that the benefit of dairy in reducing bowel cancer risk was only seen at levels over 100 grams (g) a day. Having 500 to 800g milk a day reduced bowel cancer risk by 20 to 30%. One pint, or 0.5 litres, of semi skimmed milk weighs about 550g. The effect of milk on lowering bowel cancer risk may be partly due to the calcium. But milk contains many other substances which may also play a role.
There is limited evidence that eating cheese may increase the risk of bowel cancer. It is not clear how cheese may increase the risk, but it may have something to do with the saturated fatty acids. However, other studies have found no link between cheese and bowel cancer risk.
Based on limited evidence, the WCRF classifies foods that contain sugar as a possible cause of bowel cancer.
Some studies have found an increase in risk of cancer of the large bowel (colon) for the highest intake of sugar compared to the lowest intake. But other studies have found no link between sugar and risk of colon cancer. An analysis of 13 studies found no link between colon cancer risk and sugar sweetened soft drinks.
Obesity is a cause of bowel cancer. It is estimated that 13 out of 100 bowel cancers (13%) in the UK are linked to being overweight or obese.
Body mass index (BMI) is a better measure of obesity than just your weight as it links weight and height. The link takes you to the glossary, which tells you how you can work out your BMI. The risk of bowel cancer is a third (33%) higher in people who are obese (BMI over 30) compared to those who have a healthy BMI.
People who are more physically active have a lower risk of bowel cancer. The evidence is stronger for colon cancer than rectal cancer.
Alcohol increases the risk of bowel cancer. It has been estimated that about 11 out of 100 bowel cancers (11%) in the UK are linked to drinking alcohol.
A 2011 systematic review showed a 21% increase for both colon and rectal cancers with an alcohol intake of around 1.5 to 6 UK units a day, compared to non drinkers or occasional drinkers. 1.5 units is less than one standard glass of red wine or around half a pint of beer. The risk increases further if you drink more than this.
The International Agency for Research on Cancer (IARC) classify smoking as a cause of bowel cancer. It is estimated that 8 out of 100 bowel cancers (8%) in the UK are linked to tobacco smoking. The risk is higher in current smokers compared with people who have never smoked. And the risk increases with the number of cigarettes smoked each day.
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