One aspirin a day 'can lower threat of bowel cancer'

An Oxford University study showed that taking one 300mg tablet a day for more than five years reduced incidence of the disease, which kills nearly 16,000 people a year in Britain.

Millions are already taking small doses of aspirin every day to reduce the chance of suffering a second heart attack or stroke.

However, the painkiller can have serious side-effects, including stomach bleeding. As a result, the researchers warned in The Lancet medical journal that widespread use of aspirin as a preventive treatment against bowel cancer was not recommended.

But they argued that the potential benefits might outweigh the dangers for those at increased risk of the disease through family history or other factors.

The study showed that using at least 300mg a day for five years reduced the subsequent incidence of colorectal cancer by 37 per cent overall, and by 74 per cent during the ten to 15 years after treatment.

Dr Andrew Chan, of the gastrointestinal unit at Massachusetts General Hospital, Boston, told The Lancet that the results "provide convincing evidence that aspirin, at biologically relevant doses, can reduce the incidence of colorectal cancer".

He added: "However, with the concerns about the potential risks of long-term aspirin use and the availability of alternative prevention strategies such as screening, these findings are not sufficient to warrant a recommendation for the general population to use aspirin for cancer prevention."

Professor Peter Rothwell, of the clinical neurology department at Oxford's Radcliffe Infirmary said: "Long-term follow-up is required from other trials to establish the effects of lower or less frequent doses of aspirin."

A U.S. report last month found aspirin helped to keep a range of cancers at bay including breast, ovarian and prostate cancer, as well as boosting survival rates of those who did contract the disease.

It is not clear how aspirin prevents cancer, although it is thought its anti-inflammatory qualities may play a part.

Previous UK laboratory tests found the drug makes cancer cells from the large bowel self-destruct.

It is also believed to reduce the number of adenomas - growths that can develop into cancer.