Add colon cancer to the list of maladies that aspirin keeps at bay - but how much is too much?

Aspirin is what you might call nature’s little wonder drug. It relieves pain, lowers fevers, fights heart disease and strokes, and now seems to prevent colon cancer. All that from tree bark. Sure it might cause you to bleed profusely from the gut, but it’s still one of the most trusted and widely used medicines in human history.

Acetylsalicylic acid (ASA) is derived from salicylic acid, a compound found naturally in the bark of the willow tree. Its use dates back as far as the fifth century BC, when Hippocrates himself wrote about a powder from willow bark that remedied pain and lowered fever. It was used in its natural, woody format for centuries until the 1880s, when a handful of European chemists synthesized ASA in the lab. German company Bayer finally trademarked the drug in 1899 (they lost the trademark in the economic shakeup after World War I, but bought the company that owned it in 1994).

Since its first commercial production, aspirin has remained a popular medicine for all sorts of common aches and illnesses. But the full extent of its healing powers has only been uncovered in recent years. Taken regularly, the little white pill enhances bloodflow by reducing the “stickiness” of platelets and assists arteries in remaining open, which helps to keep heart attacks and strokes at bay. Aspirin has also been touted as reducing cancer risks.

The humongous Harvard-based Nurses’ Health Study, which covers 30 years and almost 80,000 participants, found this March that women on low doses of aspirin (81-milligram “baby aspirin”) were less likely to die from heart disease, stroke or colon cancer. On the flip side, women who consumed high doses – more than 14 adult tablets (325 milligrams each) per week – didn’t receive health benefits, and were more likely to die from strokes.

On the other hand, a May study combining results from more than 7500 people found that only an adult dose of daily aspirin can lessen colon cancer risk. An Oxford University study led by Peter Rothwell found that taking 300 milligrams of aspirin every day for five years diminishes the risk of colon cancer by an astounding 74% over the following 10–15 years among both men and women.

Yet most people don’t consume that much aspirin – not because of any clinical findings but because it can lead to painful stomach bleeding. The FDA officially warned the public about this side-effect years ago. A large review published in the Journal of the American Medical Association in May found that thousands of Americans are likely sent to the ER needlessly each year for stomach bleeding and that doses higher than 75 to 81 milligrams do not improve cardiovascular health.

So if colon cancer runs in your family (or you have an overwhelming need to eat vast quantities of red meat), you might bother considering the daily adult dose. For everyone else, it seems baby is best.

