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Aspirin, colon cancer, and genetics

Colon cancer risk factors include environmental exposure (diet, toxicants, etc.) as well as genetic variants that increase or decrease your susceptibility. When it comes to preventing colon cancer, doctors often recommend dietary changes, and your doctor may also mention that studies show that taking aspirin regularly also decreases the risk of colon cancer.  Personalization is the key here, though, because that protection from aspirin may only be for people with certain genetic variants.

Should you take aspirin to prevent colon cancer?

Colon cancer is one of the most common forms of cancer, with a lifetime risk of about 5%. The good news is that survival rates are high for those who detect it early. At later stages, though, the mortality risk is high for metastasized colon cancer.[ref]

Aspirin is dirt cheap and has been used for hundred-plus years. Recently, it has been in the news as possibly preventing several types of cancer, including colon cancer.

The jury is still out, though, on whether or not to recommend aspirin to everyone as a way to prevent cancer.  The American Cancer Society currently only recommends taking low-dose aspirin for colon cancer prevention if you also would benefit from it for heart disease prevention.[ref]

What are the risks of taking aspirin for cancer prevention?

Aspirin is a blood thinner, so frequent use includes bleeding risks. This risk may be a significant detriment for older people who are at a higher risk of colon cancer due to age. For younger people, the risk of gastric bleeding each year is 1 or 2 in a thousand, but this increases to around 7 in 1000 for people over the age of 80.[ref] If you are concerned about the risk of bleeding, you should talk with your doctor and weigh the benefits vs. the risk.

Using genetics to determine the value of aspirin for colon cancer:

It turns out that genetic variants play a significant role in whether aspirin reduces the risk of colon cancer for an individual.

How exactly does aspirin affect colon cancer?

The cyclooxygenase enzymes (COX-1 and COX-2) are involved in inflammatory responses. Inflammation is an important part of the body’s immune response to trauma or pathogens. Problems arise, though, when the inflammatory process doesn’t turn off when it is supposed to.

COX inhibitors decrease inflammation and, thus, the pain associated with it. Aspirin is a COX inhibitor, along with NSAID pain relievers such as ibuprofen. Other natural COX inhibitors include Vitamin D, St. John’s Wort, and fish oil.[ref]

Research shows that COX-1 is usually associated with acute inflammation, which occurs with trauma and pathogens. COX-2 is linked to maintaining that inflammatory response.[ref]

Inhibiting COX-2 alone has been shown in studies to reduce colon cancer.[ref]

While inhibiting COX-2 may reduce colon cancer, research shows that you don’t want to block COX-2 without also inhibiting COX-1. Drugs inhibiting only COX-2, such as Vioxx, seem to increase the risk of cardiovascular events. (Vioxx was taken off the market in 2004 due to a significant increase in the risk of heart attacks and strokes.)[ref]

Aspirin and other NSAIDs inhibit both COX-1 and COX-2. Studies dating back to the mid-90s have shown that low-dose NSAID use to prevent heart disease also decreases the risk of colon cancer. The benefit ranges from a 21% decrease in risk to a 31% decrease in risk for regular aspirin or other NSAID users.[ref][ref][ref]

While research is still ongoing, there are at least two ways that aspirin and other NSAIDs reduce colon cancer risk:

  • Aspirin may reduce the ability of cancer cells to proliferate through the anti-platelet pathway. This could help to reduce the activation of the oncogene c-MYC.[ref][ref]
  • Some cancer tumors express increased levels of COX-2. For example, animal studies show that decreasing COX-2 genetically can decrease tumors formed in epithelial cells. Additional research indicates that COX2 inhibition in prostate cancer cells decreases proliferation.[ref][ref]

Aspirin Use Genotype Report:

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Dosage and Timing:

Talk with your doctor if you have questions before starting an aspirin regimen.  

If you carry the genetic variants above that reduce the risk of colon cancer with aspirin use, it may be helpful to read and understand some of the details in the epidemiological studies. Keep in mind that there may be other genetic variants that also decrease cancer risk with aspirin usage, so you can’t rule out a benefit just from your 23andMe or AncestryDNA data.

  • The studies on NSAID use show that it is repeated usage that decreases cancer risk. This isn’t a one-and-done type of situation. For some studies, the statistical benefit in reduced risk is seen after 6+ years.[ref][ref]
  • More isn’t always better…Low-dose aspirin (~75 mg) taken 4+ times per week seems to be effective and is less likely to cause gastric bleeding.[ref]

Do other natural COX inhibitors also decrease cancer risk?

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Originally published 8/2016; updated and revised 8/2020


About the Author:
Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering from Colorado School of Mines and an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.