I have spoken to three doctors about this and they all said the same thing to me: you should be taking a 325 mg tablet of aspirin daily. All three do it themselves and two of them said they have been taking a daily aspirin for more than 20 years. So do speak to your own doctor about it when you next see her/him.
David B. Agus in the New York Times:
New reports about aspirin’s benefits in cancer prevention are just as convincing. In 2011, British researchers, analyzing data from some 25,000 patients in eight long-term studies, found that a small, 75-milligram dose of aspirin taken daily for at least five years reduced the risk of dying from common cancers by 21 percent.
In March, The Lancet published two more papers bolstering the case for this ancient drug. The first, reviewing five long-term studies involving more than 17,000 patients, found that a daily low-dose aspirin lowered the risk of getting adenocarcinomas — common malignant cancers that develop in the lungs, colon and prostate — by an average of 46 percent.
In the second, researchers at Oxford and other centers compared patients who took aspirin with those who didn’t in 51 different studies. Investigators found that the risk of dying from cancer was 37 percent lower among those taking aspirin for at least five years. In a subsection of the study group, three years of daily aspirin use reduced the risk of developing cancer by almost 25 percent when compared with the aspirin-free control group.
More here.