Taking 300 milligrams of aspirin daily for 5 years might cut the risk of colon cancer by almost 40 percent, according to a new British study, and may cut the risk by almost 75 percent in people who take it for 10 to 15 years. However, the researchers warn that this type of therapy is only recommended for people at high risk of developing colon cancer, as long-term use of  higher levels of aspirin therapy has potential dangers, such as gastrointestinal bleeding.