Taking between half and one-and-a-half aspirin tablets per week could be the key to preventing gastrointestinal cancers including colon cancer, new research suggests.
A large-scale study spanning more than 30 years found that people who took aspirin for several years were less likely to develop colon cancer. They also had a lower risk of developing cancer in general.
The study echoes previous research which links aspirin use to a reduced cancer risk.
Aspirin is commonly used to relieve pain and reduce inflammation, the latter of which might influence cancer risk.
Researchers looked at data from 1986 of 88,084 women (aged 30-55) and 47,881 men (aged 40-75) participating in two large studies.
During 32 years of follow up, there were 20,414 cancers among women and 7,571 among men.
People who took aspirin regularly were 3% less likely to develop cancer than those who didn't take it.
The drug was not linked to a reduced risk of breast, advanced prostate or lung cancer.
Regularly taking aspirin was associated with a 15% reduced risk of developing gastrointestinal tract cancers. This, scientists said, was due to a 19% reduced risk of colon cancers.
Senior author Dr Andrew Chan, of Massachusetts General Hospital,told Reuters: "We did find that aspirin reduced someone's risk of developing cancer overall.
"Much of that reduced risk is of cancers of the gastric system."
Dr Chan said aspirin may also affect prostaglandins, which are natural compounds with a role in the development of colon cancer.
Researchers believe aspirin could compliment colon cancer screening.
They estimate that 17% of colon cancers could be prevented with regular aspirin use among people who don't get colonoscopies.
About 9% of colon cancers could be prevented with regular aspirin use among people who do get screened.
In the study, which was published in the journal JAMA Oncology, a reduced risk of developing gastrointestinal cancers was linked to taking 0.5-1.5 aspirin tablets per week for at least six years.
Chan said: "What it looks like is even reasonably low doses like a baby aspirin a day has some benefit. What's unclear is if higher doses have more of an effect. I think that question is still open."
Nicola Smith, Cancer Research UK’s senior health information officer, commented on the study: "It adds to what we know about the potential for long-term aspirin use to reduce the risk of cancer, particularly bowel cancer, though it didn’t consider the risk of side effects such as internal bleeding.
"We need to understand more about who would get the best balance of benefits and risks of side effects, how much aspirin they should take, and for how long."
A 2014 study estimated that if everyone in the UK aged 50 to 64 took aspirin for 10 years, roughly 130,357 cancer deaths could be avoided over two decades.