A cursory reading of headlines makes it seem that taking aspirin regularly is a great way to stay healthy. It helps prevent heart disease in men, stroke in women and, according to new studies, colon cancer, too. All that’s true -- but it is not all that simple.

We’re already quite familiar with both the benefits and associated risks of using aspirin to help prevent cardiovascular problems, but its effectiveness for keeping colon cancer away is newsworthy... or is it? I’d heard some caveats about this finding so I called one of the country’s leading investigators on the matter, Andrew T. Chan, MD, MPH, assistant professor of medicine at Harvard Medical School, to get the whole story.

Does Aspirin Prevent Colon Cancer?

Dr. Chan has led extensive research on aspirin and colon cancer, and has found that long-term aspirin use -- taking at least 325 mg (the adult dose) daily for six or more years -- significantly reduces risk in both men and women.

As we know, aspirin has many different mechanisms. According to Dr. Chan, in the case of cancer its efficacy relates to the drug’s ability to block passages of certain enzymes important in the inflammatory process -- in particular cyclooxygenase-2 (COX-2). High levels of COX-2 can be found in most colorectal tumors, but not in colon tissue. COX-2 seems to promote cancer by supporting blood vessels in tumors and may also help tumors spread to surrounding tissues. Aspirin blocks growth pathways.

However colon cancer is a slow-growing disease, generally starting five to 10 years before diagnosis. Dr. Chan’s study found that when people stop the daily aspirin therapy, within just four years their risk reverts to its original level. Therefore, Dr. Chan says that for most people, taking aspirin to prevent colon cancer is not a recommendation -- you’d need to take a lot in order to decrease your cancer risk, and large doses of aspirin carry a risk for internal bleeding. Furthermore, says Dr. Chan, there are plenty of other things you can do to prevent colon cancer, leading him to conclude that "there are few patients for whom it makes sense to take aspirin as the only means of prevention."

Going Natural

Researchers are always on the hunt for natural ways to decrease risk. A group at the Rowett Research Institute of Nutrition and Health in Aberdeen (Scotland) found in 2006 that a particular curry in India is rich in salicylic acid (the chemical from which aspirin, acetylsalicylic acid, is made), a fact that might help explain low rates of colon cancer in that country. Dr. Chan observes that since aspirin is from a natural product (willow bark), it isn’t surprising to find similar compounds and properties in foods. But relying on foods as a source of salicylic acid makes it impossible to know if the amount you’re ingesting is too little, too much or just right. In the future, though, he says we may find dietary sources that offer "a little bit of a boost without aspirin’s troubling side effect."

A good strategy, says Daily Health News contributing medical editor Andrew Rubman, ND, is to limit intake of processed and broiled meats and trans fats, all of which have been linked to increased risk for colon cancer. Dr. Rubman also suggests increasing intake of wheat-bran fiber and fruits and vegetables and taking fish oil, which seems to blunt COX-2 activity and the production of cancer-promoting hormones.

In summary, aspirin therapy isn’t for everyone. It can cause internal bleeding that may be dangerous, even lethal. Its preventive properties differ depending on your gender and there are important caveats that apply to its value in holding back colon cancer. If you heard about the benefits but didn’t pick up on the risks in the media reports, you may have missed the most important parts of the story.