Should You Take Aspirin for Cancer Prevention?

Should you take aspirin for cancer prevention?

An important study published earlier this year indicated that people who take aspirin every day reduce their risk of cancer by 21%. That is an amazing statistic! And it seems like an easy, inexpensive thing to do, with very little risk. But should you take aspirin to prevent cancer?

Researchers conducted this study to settle a discrepancy in the research. Several studies had shown that taking aspirin every day for more than five years reduces the risk of developing colorectal cancer. Animal studies also have confirmed that aspirin has a cancer-preventing effect.

Another study, however, showed a different result. In this case, the Women’s Health Study followed a huge number of women. The researchers studied the effect of aspirin on 40,000 women for 10 years. Half the women received 100 mg of aspirin every other day, and the other half received a placebo. They found that aspirin for cancer showed no effect at all. In other words, this massive study says aspirin doesn’t prevent cancer in any way.

So what’s the right answer? Does aspirin prevent cancer or not? To help settle the issue Researchers at the University of Oxford conducted this meta study.

They reviewed the data of every published placebo-controlled trial of four years or longer that looked at the effect of aspirin for cancer prevention. Eight of the trials included a total of 25,570 men and women. When the researchers broke down the data to individual patients, they figured out what was going on. First, in order for aspirin to have its effect, you have to take it for at least five years. And, second, unlike they did in the Women’s Health Study, you have to take it every day. The researchers also noted that there was no additional benefit to taking more than 75 mg of aspirin per day.

In the end, the people taking aspirin in these trials were 21% less likely to have died from cancer. So does that mean it’s a good idea to take 75 mg of aspirin a day to prevent cancer?

Animal studies indicate that the reason aspirin is effective in preventing some cancers is because it inhibits the pro-inflammatory enzyme cyclo-oxygenase. I routinely test all of my cancer patients to determine if their cancers are susceptible to this inhibition. And more often than not, they are. So aspirin would be a good choice for therapy in these patients. That is if it were not for the side effects of taking aspirin on a regular basis.

One study published a few years ago looked at people who were taking low-dose aspirin as a preventive strategy for heart disease. The researchers performed an endoscopy (a tube with a camera that goes down the throat into the stomach) on the patients and found that 11% had ulcers. This was true even though none of them had any symptoms suggesting ulcers. That study shows us that if you take low-dose aspirin, such as the 75 mg recommended by the meta study, the odds are one-in-ten that you will have an ulcer even though you don’t have any symptoms.

In another similar trial, people taking low-dose aspirin were close to three times more likely to have a major bleeding episode from an ulcer than those taking the placebo.

I think these odds are scary. In fact, that’s the same conclusion that most of the researchers in this area come to: aspirin prevents cancer, but the dangers counter its benefits.

So should you take aspirin to prevent cancer? I don’t think so. Instead, there are other nutrients you can take to accomplish the same thing as aspirin, without the side effects.

Rothwell PM, Fowkes FG, Belch JF, Ogawa H, Warlow CP, Meade TW. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Lancet. 2011 Jan 1;377(9759):31-41. Epub 2010 Dec 6.
Yeomans ND, Lanas AI, Talley NJ, et al. Prevalence and incidence of gastroduodenal ulcers during treatment with vascular protective doses of aspirin. Aliment Pharmacol Ther. 2005;22:795-801.
Baigent C, Blackwell L, et al. Aspirin in the primary and secondary prevention of vascular disease: collaborative meta-analysis of individual participant data from randomised trials. Lancet. 2009;373:1849-1860.
Lanas A, Scheiman J. Low-dose aspirin and upper gastrointestinal damage: epidemiology, prevention and treatment. Curr Med Res Opin. 2007;23:163-173.

Dr. Shallenberger has practiced medicine for more than 35 years, and has his own wellness clinic, The Nevada Center for Alternative and Anti-Aging Medicine. Dr. Shallenberger also writes the monthly newsletter Real Cures. For information about Real Cures Letter, visit the website at

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