Under certain conditions, taking one aspirin per day for up to a decade can significantly reduce the risk of developing cancers of the digestive tract, including stomach and throat cancer, scientists in the UK announced Tuesday. Doctors have known about aspirin's potential health benefits, but the new study is the first to confirm those benefits outweigh the negatives — namely, stomach bleeding that is fatal in a small number of cases.

"Until our study, where we analysed all the available evidence, it was unclear whether the pros of taking aspirin outweighed the cons," said lead author Jack Cuzick, of Queen Mary University of London, in a statement. "Whilst there are some serious side effects that can't be ignored, taking aspirin daily looks to be the most important thing we can do to reduce cancer after stopping smoking and reducing obesity, and will probably be much easier to implement."

Here's what they found:

  • Taking aspirin every day for 10 years could reduce the risk of bowel cancer by 35 percent and deaths from that cancer by 40 percent. Throat and stomach cancer was reduced 30 percent with the number of associated deaths cut by up to half.
  • While the exact, most helpful daily dosage is unclear, "the evidence shows people need to start taking a daily dose of 75 to 100 mg for at least five years and probably 10 years between the ages of 50 and 65." For the first three years, there's no obvious benefit. "Death rates were only reduced after five years," according to the news release.
  • The risks of taking aspirin so often were also apparent from the data they reviewed. "Amongst 60-year-old individuals who take daily aspirin for 10 years," digestive tract beleeding increased up to nearly four percent. Among these indivuals who bled, just five percent died from the complication. The risk of bleeding increases after age 70.
  • "Another side effect of aspirin use is peptic ulcer, the risk of which is increased by 30 to 60 percent."

Despite the concerns, the authors, who specialize in cancer prevention, say the potential to save lives wins out. The data they used were based, in part, upon clinical trials. Their study appears in the journal Annals of Oncology.

As recently as June, however, other researchers exploring the topic have warned against using aspirin as a cancer ward, saying it should be considered only in certain patients, like those with a family history of cancer. "The American Cancer Society ... does not recommend taking aspirin specifically to prevent cancer," Eric Jacobs, a director of drug treatments at the organization, told HealthDay. "People thinking about taking aspirin on a regular basis should talk to their health care provider, who can take their individual medical history into account when weighing the overall benefits and risks of using aspirin."

Cuzick and his colleagues also said it's imperative to consult with one's doctor before trying daily aspirin. They acknowledged the need for more research that could lead to methods for preventing bleeding and could reveal a precise recommended dosage. But their optimism about the drug is clear.

"If everyone aged between 50 to 65 started taking aspirin daily for at least 10 years, there would be a nine percent reduction in the number of cancers, strokes and heart attacks overall in men, and around seven percent in women," Cuzick said. "The total number of deaths from any cause would also be lower, by about four percent over a 20-year period. The benefits of aspirin use would be most visible in the reduction in deaths due to cancer."

Source: Cuzick J, Thorat MA, Bosetti C, et al. Estimates of benefits and harms of prophylactic use of aspirin in the general population. Annals of Oncology. 2014.