Taking aspirin can significantly reduce a person's risk of developing major cancers of the digestive tract, such as bowel cancer, a new study has found.

The drug also reduces the risk of dying from these cancers.

This marks the first time that scientists have reviewed all the evidence contained in studies and clinical trials relating to the preventive use of aspirin.

They found that taking the drug for 10 years reduced bowel cancer cases by 35% and bowel cancer deaths by 40%. Rates of stomach and oesophageal cancer cases also fell by 30%, while deaths from these cancers fell by between 35% and 50%.

The scientists from Queen Mary University of London found that in order for a person to see these benefits, they needed to start taking a 75-100mg dose of aspirin every day for at least five years, and probably 10 years, between the ages of 50 and 65.

No benefits were recorded in the first three years of taking the drug and death rates only began to fall after five years.

The scientists did warn that taking aspirin in the long-term increases the risk of bleeding from the digestive tract. They pointed out that a 60-year-old who takes aspirin every day for 10 years sees their risk of digestive tract bleeds, such as stomach bleeding, increase from 2.2% to 3.6%. This could be life threatening in a very small number of people - less than 5%.

The long-term use of aspirin can also increase the risk of developing a peptic ulcer by 30-60%.

The study was unable to determine whether taking aspirin for longer than 10 years lead to greater benefits.

"It has long been known that aspirin - one of the cheapest and most common drugs on the market - can protect against certain types of cancer. But until our study, where we analysed all the available evidence, it was unclear whether the pros of taking aspirin outweighed the cons.

"Whilst there are some serious side-effects that can't be ignored, taking aspirin daily looks to be the most important thing we can do to reduce cancer after stopping smoking and reducing obesity, and will probably be much easier to implement," commented lead scientist, Prof Jack Cuzick.

He said that the study showed that if everyone aged between 50 and 65 started taking aspirin every day for at least a decade, ‘there would be a 9% reduction in the number of cancers, strokes and heart attacks overall in men and around 7% in women'.

"The total number of deaths from any cause would also be lower, by about 4% over a 20-year period. The benefits of aspirin use would be most visible in the reduction in deaths due to cancer," he pointed out.

Prof Cuzick added that people should consult their doctor before taking aspirin on a daily basis to help determine if they are at an increased risk of bleeding.

Details of these findings are published in the journal, Annals of Oncology.