It might be time to rethink that little pill in your medicine cabinet.
A new study casts doubt on the idea that regularly taking an over-the-counter painkiller can help ward off colorectal cancer — at least for the general population.
Worse, researchers warn that the daily habit carries “immediate risks,” including a higher chance of dangerous bleeding in and around the brain.
“As scientists, we must follow the evidence where it leads,” Dr. Bo Zhang, a researcher at the West China Hospital of Sichuan University and senior author of the study, said in a statement.
“Our rigorous analysis of the highest-quality trials reveals that the ‘aspirin for cancer prevention’ story is more complex than a simple ‘yes or no’,” he continued.
To get answers, Zhang and his team reviewed 10 randomized controlled clinical trials involving 124,837 people. Each study looked at whether regularly taking aspirin could prevent colorectal cancer or precancerous growths known as polyps in average risk adults.
Aspirin, a common nonsteroidal anti-inflammatory drug available without a prescription in the US, is best known for easing headaches, fevers and inflammation from conditions like arthritis.
But for years, scientists have also explored whether it could double as a cancer fighter.
The thinking is simple: long-term inflammation is believed to help tumors grow, and drugs like aspirin and ibuprofen reduce inflammation.
Some earlier research suggested low-dose daily aspirin might help people with a higher genetic risk of colorectal cancer, cutting their chances of developing the disease or stopping it from returning.
But for the average person, the new review found that aspirin probably doesn’t lower the risk of colorectal cancer during the first five to 15 years of use.
Some studies hinted at protective effects after a decade or more. However, the researchers noted that those findings came from observational follow-ups, when participants may have changed their aspirin use or added other treatments — muddying the data and leaving results open to bias.
“My biggest worry is that people might assume that taking an aspirin today will protect them from cancer tomorrow,” Zhang said.
“In reality, any potential preventive effect takes over a decade to appear, if it appears at all, while the bleeding risk begins immediately.”
And that bleeding risk is no small matter.
The researchers found that daily aspirin use increases the risk of serious extracranial hemorrhage, or bleeding outside the skull, and likely raises the chance of a hemorrhagic stroke.
These life-threatening strokes occur when a blood vessel in the brain bursts, flooding surrounding tissue with blood, increasing pressure inside the skull, and often causing lasting damage.
Older adults and people with a history of ulcers or bleeding disorders may be especially vulnerable to these risks from regular aspirin use.
“This review reinforces that we must move away from a one-size-fits-all approach,” said Dr. Dan Cao, senior author of the study. “Widespread aspirin use in the general population simply isn’t supported by the evidence.”
The researchers are urging patients to speak with a health care provider about their personal bleeding risk before taking aspirin for cancer prevention.
“The future lies in precision prevention — using molecular markers and individual risk profiles to identify who might benefit most and who is most at risk,” Cao said.
The warning comes as colorectal cancer rates are climbing among young people, driving many to search for ways to protect themselves.
In the US, it’s now the leading cause of cancer death in adults under 50, surpassing breast and brain cancers after steady increases over the last two years.
The good news: Aspirin isn’t the only tool at your disposal. Research suggests that up to half of all colorectal cancers in the US could be prevented each year through simply lifestyle changes.
That includes maintaining a healthy weight, exercising regularly, getting enough sleep, limiting alcohol and cutting back on ultra-processed foods.
Knowing the early warning signs and keeping up with screening is also key. The US Multi-Society Task Force on Colorectal Cancer recommends that average-risk Americans start screening at age 45.
There are several options, including non-invasive stool tests, but colonoscopies remain the gold standard. They can help doctors catch cancer early, before symptoms start to appear, and even prevent it from developing by removing precancerous growths.
The stakes are high. In 2026 alone, the American Cancer Society estimates that 158,850 new cases of colorectal cancer will be diagnosed it the US, and 55,230 people will die from the disease.
