A study which looked at more than 1,000 people also found that aspirin use was associated with an 11 percent lower risk of cardiovascular disease.
In the experiment some of the patients were given aspirin, others a non-active placebo and a third group had no treatment at all.
It was found that around 250 patients needed to be treated with aspirin for five years to prevent a single heart attack, stroke or death caused by cardiovascular disease, researchers said.
However, the increased use of aspirin resulted in one in 200 people suffering a major bleed - a 43 percent increase compared to those who did not take aspirin.
Taking too much aspirin is known to thin blood and increase the risk of intestinal bleeding.
Lead researcher Dr Sean Zheng, from King's College London, said the study showed there was “insufficient evidence to recommend routine aspirin use in the prevention of heart attacks, strokes and cardiovascular deaths in people without cardiovascular disease.”
Dr Zheng added that the risk of severe bleeding needed to be explained to patients before they take the drug.
"There has been more uncertainty surrounding what should be done in patients who are at higher risk of cardiovascular disease and in patients with diabetes. This study shows that while cardiovascular events may be reduced in these patients, these benefits are matched by an increased risk of major bleeding events,” he added.
Commenting on the findings, which were published in the Journal of the American Medical Association, Professor Stephen Evans, from the London School of Hygiene & Tropical Medicine, said the where the balance tips would be different for individual patients.
"The message for healthy patients is that taking aspirin has a small benefit to prevent heart disease but also at least as large harm in terms of serious bleeding,” Prof Evans said.
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