Aspirin a day may not be so good for heart Taking aspirin every day may not be worth the risk for those with no history of heart problems, a major study has concluded. The findings, by a team at St George's, University of London, add to evidence that, for healthy people, the dangers associated with aspirin can outweigh the benefits. The drug, which thins the blood and helps prevent clotting, is a standard treatment for heart attack or stroke patients. Doctors have also prescribed it to healthy people as a purely precautionary measure. But the study, based on data from nine clinical trials involving more than 100,000 participants, found that long-term use of aspirin can lead to stomach ulcers and internal bleeding.