Researchers say taking an aspirin every day decreases the risk of gastrointestinal cancers like colon cancer, but it doesn’t reduce the growth of cancerous cells elsewhere in the body.

An aspirin a day can help keep the cancer away but only in certain parts of the body.

A new study published today in JAMA Oncology states daily doses of aspirin for at least six years can result in a 15 percent lower risk for cancer in the gastrointestinal region. That includes a 19 percent decrease in risk for cancer of the colon and rectum.

However, researchers said aspirin was not associated with a lower risk of other major cancers, including breast, prostate, and lung. Generally speaking, the report said the aspirin regiment was associated with a 3 percent lower risk for all cancers.

Researchers said there may be risk factors associated with gastrointestinal cancers that are not prevalent with other types of cancer.

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The researchers from Massachusetts General Hospital looked at 135,965 men and women from two large U.S. studies of healthcare professionals.

There were 20,414 cancers among the 88,084 women and 7,571 cancers among the 47,881 men during the 32-year follow-up research.

The research on cancer risk focused on people who took aspirin at least two times a week.

Dr. Andrew T. Chan, M.P.H., program director of the gastroenterology training program at Massachusetts General, and one of the authors of the study, told Healthline there are two possible major factors for aspirin’s effect on gastrointestinal cancers.

One is inflammation, which is associated with some cancer growths. Aspirin, of course, has anti-inflammatory properties.

The other factor is a protein found in the colon and other gastrointestinal areas that may encourage cancer cell growth. Aspirin blocks the production of this protein.

“There appear to be pathways that are unique to cancers that develop in the gastrointestinal system,” Chan said.

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Eric Jacobs, PhD, the American Cancer Society’s strategic director of pharmacoepidemiology, told Healthline that the Massachusetts study backs up previous research showing long-term aspirin use can reduce gastrointestinal cancer risk.

However, he noted daily aspirin use has both harmful and beneficial uses. Among the potential problems are gastrointestinal bleeding and stomach ulcers.

The American Cancer Society doesn’t have a formal recommendation regarding aspirin use to lower cancer risk.

Jacobs noted that people who have had a heart attack or stroke will sometimes be told to take aspirin on a regular basis. Some patients in their 50s with a higher risk of cardiovascular disease will also be told to start a long-term regimen of low-dose aspirin.

Overall, he said, people should weigh the risks and benefits before starting a daily dose of aspirin.

“This makes more sense than thinking about taking aspirin just for the prevention of cancer,” Jacobs said in an email to Healthline.

He added that aspirin should not be considered a substitute for a good diet, stopping smoking, or getting cancer screenings.

Chan agreed.

“Aspirin can be seen as a compliment,” he said. “By no means is it a substitute.”

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