Researchers from the Women's Health Study assigned nearly 39,000 women either aspirin or a placebo taken on alternate days.
After 18 years they found that the women who consistently took the aspirin had a 20 percent lower incidence of colorectal cancer versus those in the placebo group.
Researchers warn that some of the women taking aspirin showed a minor increase in gastrointestinal bleeding and peptic ulcers, adverse effects of taking the medication.
