Nearly one-fifth of all Americans – roughly 60 million people – take low-dose aspirin every day to help ward off heart disease. Now, new studies show popping a baby aspirin daily can help prevent cancer. But should you really take aspirin that often? Here's how to tell if daily low-dose aspirin is right for you.

Cancer
A series of large recent studies shows that people who take 75 mg of aspirin daily for at least five years reduce their risk of dying from cancer by about 20 percent. Other research has concluded that people who take daily aspirin have a 41 percent lower chance of getting liver cancer, specifically, than non-aspirin users. Researchers think aspirin helps prevent cancer by reducing inflammation that may cause the disease.

Despite these impressive numbers, the American Cancer Society says no one should start taking daily aspirin for cancer. The drug, even in a baby dose – 81 mg – increases the risk of internal bleeding, ulcers, and one type of stroke. A recent study of more than 100,000 people found taking aspirin daily boosts your chance of debilitating or life-threatening bleeding by 30 percent. "We don't know how long you take it before the prevention starts, and how long the prevention lasts after you stop taking it," says cancer-study specialist Dr. John Baron of the School of Medicine at the University of North Carolina. "It can take years of taking aspirin for the cancer benefits to begin – but that could be 10 years of bleeding without benefits, and that's a problem."

What to do? Wait for the research, says Dr. Baron. "My guess is that when the work is done, aspirin will be judged worthwhile, maybe to start taking around age 50. But there will need to be the appropriate warnings about the likely side effects and toxicity."

Heart Disease
If you haven't had a heart attack or don't have any risk factors for heart disease, like high cholesterol or high blood pressure, you probably shouldn't take low-dose aspirin, says New York cardiologist Dr. Dennis Goodman, because the risks outweigh the potential benefits. "Aspirin is not a benign medication – otherwise, we'd all be taking it. But if you talk to any gastroenterologist, they'll tell you it's the most common cause of serious stomach bleeding and upper-GI procedures." Indeed, studies show daily low-dose aspirin raises the risk of severe bleeding more than it will lower your risk of having a heart attack.

If you have had a heart attack, take aspirin, says Goodman. "Aspirin is probably one of the most effective and cost-effective treatments for people with heart disease or high-risk factors for heart disease. But again, it's not indicated for everyone."