Protecting against bowel cancer

People who exercise more have a lower risk of bowel cancer. One study pooled the results of over 50 other research projects and included over 100,000 cases of bowel cancer in total. It provides the strongest evidence yet of the role of exercise, with the risk of bowel cancer being 50% lower in people who exercised regularly – half the risk. This lower risk remained even when other factors such as diet, smoking and obesity were taken into account.

The other good news is that any decent exercise will do. The studies included manual work, hiking and gardening as well as sports. We don't know why exercise helps. It may affect your hormone levels. Or it may change the speed at which your body ticks over (your metabolic rate). Or it may even change the time your food stays in the bowel.

NSAIDs are anti inflammatory drugs such as ibuprofen (Nurofen). Aspirin is also an anti inflammatory drug. We know from research that these drugs may help to prevent bowel and other digestive system cancers. We don't know quite how this works. There is a theory that this type of drug stops an enzyme called COX-2 from working. Blocking the enzyme may help to stop polyps developing. Polyps can develop into cancer. Trials are looking into this further. 

At least 2 trials using aspirin have found it lowers the risk of developing bowel polyps. A 2010 review of trials found that taking low dose aspirin for a few years reduced the risk of colon cancer but not rectal cancer. It also reduced the number of people who died from bowel cancer. But aspirin does have side effects and it is not yet clear how safe it is to take even low doses. Research is looking into this. 

You should not take aspirin or other NSAIDs regularly without checking with your doctor first. These drugs can damage the lining of your stomach and cause bleeding. Doctors don't currently recommend routinely taking aspirin or other NSAIDS to prevent bowel cancer unless you are part of a clinical trial. For many people, the risk of damage to the stomach lining outweighs the benefit of preventing bowel cancer. 

Some cancer prevention trials are listed on our clinical trials database. If you want to search only for prevention trials, you will need to use the advanced search option.

Hormone replacement therapy (HRT) and the contraceptive pill may protect against bowel cancer. Compared with women who have never used them, the evidence suggests that women who have used HRT or the pill have a 20% lower risk of bowel cancer. But we need more research to be sure.

Female hormones may protect against bowel cancer by helping to lower the concentration of bile in the bowel. Although we need it for the healthy digestion of fats, bile irritates the lining of the bowel.

Although HRT may reduce bowel cancer risk, there are other health issues to take into account when deciding to take HRT. It increases your risk of breast cancer and other illnesses. Before making a decision about whether to take HRT, you should talk to your doctor about the overall effect it could have on your health.

Several studies have shown that people with higher levels of vitamin D have a lower risk of bowel cancer. You get a small amount of vitamin D from your diet. But your body also makes vitamin D in response to the sun. You don't need to sunbathe to get enough vitamin D. A short time outdoors a few times a week should be enough. Your body only makes as much vitamin D as it needs. So spending too long in the sun and getting burnt will not help with vitamin D levels, but will increase your risk of skin cancer.

We know from research that people taking part in bowel screening programmes using the faecal occult blood test have a 25% lower risk of dying of bowel cancer than people who don't have screening.

Smokers are more likely to develop polyps in their bowel than non smokers, and some studies show that smokers have a higher risk of bowel cancer. So giving up smoking can reduce your risk of bowel cancer. If you want to give up smoking you can find tips and information on the Cancer Research UK website.