Intake of aspirin and omega-3 is safe and effective at reducing chances of bowel cancer in high-risk patients, according to a new clinical trial.

In the trial, published in the journal The Lancet, these low-cost drugs reduced the number of pre-cancerous polyps -- a small growth, usually benign -- in patients found to be at high risk of developing bowel cancer. The findings showed that patients who took aspirin had 22 percent fewer polyps compared to those who took the placebo.

Those who took omega-3, also called EPA (eicosapentaenoic acid) had 9 percent fewer polyps compared to those who took the placebo. Although aspirin and EPA had beneficial effects on polyp numbers individually, the combination of aspirin and EPA together appeared to have an even greater effect, as it provided another layer of prevention, alongside colonoscopy, the researchers said.

"The trial demonstrates that both aspirin and EPA have preventative effects, which is particularly exciting given that they are both relatively cheap and safe compounds to give to patients," said Mark Hull, Professor at the University of Leeds in the UK.

In the trial, the team included over 700 patients, all of whom had a higher risk of developing bowel cancer after having a colonoscopy. Participants took either a 300-milligram aspirin tablet, 2 grams EPA in four capsules, a combination of both aspirin and EPA, or placebos only.

The results showed both aspirin and omega-3 reduced the number of bowel polyps in patients one year on from a screening colonoscopy (large bowel camera test). However, they did not reduce the chances of an individual having any polyps present in the bowel.

Importantly, treatment with aspirin and EPA was safe with no increased bleeding risk. However, individuals who took EPA on its own had a slight increase in stomach upset symptoms. Further research is needed to test aspirin and EPA treatment together for polyp prevention, the researchers noted.