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Food types and bowel cancer

Men and women discussing 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

 

A quick guide to what's on this page

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 probably lowers 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 may reduce the risk of bowel cancer
  • Body weight and exercise – people who are overweight or obese have an increased risk of colon cancer, particularly men. Being physically active lowers colon cancer risk
  • Alcohol and smoking also increase bowel cancer risk

CR PDF Icon You can view and print the quick guides for all the pages in the about bowel cancer section.

 

 

Fibre and bowel cancer

Fibre is found mostly in fruit, vegetables and cereals, including flour and bread. A lot of research has looked at fibre and bowel cancer.

Recent research from the World Cancer Research Fund, including EPIC (the European study into the effect of diet on cancer risk), has suggested that fibre protects against bowel cancer. More than 8 separate studies showed that people who ate the most fibre had the lowest bowel cancer risk. And those who ate the least had the highest bowel cancer risk. The foods studied were all natural foods, such as fruit, vegetables and cereals, and not fibre supplements or foods with artificially added fibre. 

In November 2011 a large meta analysis looked at fibre and bowel cancer risk. It included 25 studies and the findings supported the EPIC study. In people who had a high intake of dietary fibre, in particular cereal fibre and whole grains, there was a lower risk of bowel cancer. 

So, 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

  • 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.

Loaf of bread - fibre

 

Fruit and vegetables

Eating more fruit and vegetables may lower the risk of bowel cancer, according to results from the EPIC study. But the evidence is not conclusive. 

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 about 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. There is quite strong evidence that a diet rich in folate is linked to a lower risk of bowel cancer. Folate is a B vitamin found in green and leafy vegetables.

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. These are called flavonoids, phyto oestrogens and tannins. We don't know whether these help to prevent bowel cancer.

Plate of fruit - fibre

The World Cancer Research Fund report in 2010 concluded that garlic probably protects against bowel cancer. But more studies are needed.

 

Meat and fish

There is strong evidence that eating a lot of red meat and processed meats increases bowel cancer risk. In 2011, it was estimated that around 1 in 5 bowel cancers were linked to eating these types of meat. Red meats include lamb, pork, veal and beef. Processed meats include sausages, salami, ham, bacon, paté and tinned meat. 

Poultry meats, such as chicken and turkey, probably don't increase your risk of bowel cancer.

Results from the EPIC study showed that people who eat fish at least every other day on average, lower their risk of bowel cancer by about a third compared to people eating fish about once a fortnight. Other studies show that the more fish people eat, the lower their risk of bowel cancer. But a review by the World Cancer Research Fund (WCRF) found the results of these studies to be inconsistent. 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. Foods cooked at very high temperatures can form chemicals called polycyclic hydrocarbons and aromatic amines. These chemicals are thought to increase cancer risk, but studies have not linked them specifically to bowel cancer.

 

Fats

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.

 

Body weight and exercise

There is a strong link between obesity and cancer of the large bowel (colon cancer), especially in men. 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.

Compared to men of a healthy bodyweight, overweight men (with a body mass index of 25 or higher) have a 25% increase colon cancer risk. Obese men (with a BMI of 30 or higher) have a 50% increased risk of colon cancer. There is a smaller risk increase for colon cancer in overweight and obese women.

People who are more physically active are at lower risk of colon cancer. But being active appears to have no effect on the risk of developing rectal cancer.

 

Calcium and vitamin D

Calcium may protect against bowel cancer, according to the World Cancer Research Fund. 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.

 

Dairy

There is some evidence that drinking milk reduces the risk of 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.

 

Sugar

It is unclear if sugar intake is linked to bowel cancer risk. Two meta analyses have looked at sugar in the diet and colon cancer risk. One of the studies found an increase in risk for the highest intake of sugar compared to the lowest intake. But the second study found no link.

 

Alcohol and smoking

Alcohol increases the risk of bowel cancer. It has been estimated that about 11% of bowel cancers 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 1.6 to 6.2 UK units a day, compared to non drinkers or occasional drinkers. 1.6 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.

Several large reviews of research into smoking and bowel cancer show that smoking also increases bowel cancer risk. It seems to have a greater effect on rectal cancer risk than colon cancer risk.

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Updated: 30 September 2013