Many Americans have tossed apples out of that old proverb about what keeps the doctor away, and they've inserted aspirin.

However, an aspirin a day can be more harmful than helpful, as a front-page story on the oft-touted wonder drug emphasized on Jan. 17. Researchers in London shared new studies showing that frequent aspirin users, even those taking low doses, were about 30 percent more likely to have major intestinal bleeding.

While an apple a day won't do any harm, aspirin is a drug and can pose health risks. So, before taking it daily, talk it over with your primary care physician. That's the message from Dr. Michael Wilkes, a longtime contributor to The Bee and a professor of medicine at the University of California, Davis.

"Even though aspirin is available over the counter without a prescription," Wilkes told The Bee, "it is a powerful medicine with a long and rich history."

Wilkes said he's had to counsel patients against taking aspirin.

"For most of us with no history of heart disease," he explained, "there is a trade-off that needs to take into account your risk factors, age, family history and your own preferences. Whether or not to take aspirin requires shared decision-making with your doctor because there are significant trade-offs."

Wilkes talked more about those trade-offs and answered other questions in this Q&A with The Bee.

Aspirin has been a staple in U.S. homes for a long time. How did it come to be used as a medicine?

Each year, billions of aspirin tablets are taken by people around the world for a variety of medical problems – some hoping to prevent heart attacks and strokes.

While the details of aspirin's discovery are a bit unclear, the drug's roots go back to ancient Greece and the effects of willow bark. Different countries claim credit for the discovery, but modern-day aspirin was developed nearly 100 years ago by chemists in the German research lab of Friedrich Bayer & Co.

Bayer's company began the testing and mass manufacturing of aspirin to bring down fevers. At the time, fevers were thought to be a serious disease rather than merely a symptom of a disease. The thinking went that if you reduced a fever, you prevented the destruction of tissues from high temperatures and thus treated the disease.

It took years for doctors to adopt the germ theory and eventually to figure out that fevers were a symptom of an infection, not a disease needing treatment. Most fevers are not in and of themselves harmful, and many fevers may be helpful.

Not long after large numbers of people began taking aspirin, doctors began to notice other effects. Many people reported the drug had a powerful effect on reducing pain from injuries, while others reported a new pain in their stomach area and intestinal bleeding.

How does aspirin work?

The discovery of how aspirin works won British scientist John Vane a Nobel Prize in Medicine in 1982.

Pain serves a purpose, warning you to prevent more serious injury to your body. The body is wired to communicate a message of pain quickly to the brain so it can take corrective action. To simplify a complex series of events, when the body is injured, say from closing your thumb in a drawer, damaged cells in the area release a protein called cyclo-oxygenase, which in turn creates other chemicals called prostaglandins.

These prostaglandins do several things including triggering nerve endings to send a message of pain to the brain, and increasing swelling and inflammation at the site of the injury.

When you take an aspirin tablet, it is absorbed into your stomach and it circulates widely in the blood until it finds places where prostaglandins are being produced – for example at sites of injury. Because aspirin slows the production of prostaglandins, it diminishes the feeling of pain and inflammation.

How does aspirin work to prevent heart attacks or strokes?

Aspirin has effects on many tissues in the body.

In the blood, aspirin slows blood clotting. In some situations, slowed blood clotting can cause problems. For example, when clotting is slowed, a cut to the skin may bleed for a longer period of time.

At the same time, by delaying clotting, aspirin can prevent heart attacks and strokes. In partially blocked blood vessels, plaque can suddenly rupture, which can cause a blood clot to form. The clot in the vessel prevents the flow of oxygen to the brain (causing a stroke) or to the heart (causing a heart attack).

Should everyone take a daily aspirin?

No, that would be too easy. Some people should never take aspirin – for example, those with allergies to it, those with severe stomach problems and those who bleed easily.

For others who have already had a heart attack, there are substantial benefits of daily aspirin. But there are significant trade-offs.

What sort of trade-offs?

The use of aspirin to prevent heart attacks and strokes for people who are otherwise healthy (have no heart disease) has been carefully studied in tens of thousands of people. The data suggest that regular use of aspirin reduces heart attacks by about 10 percent. Not bad. But this reduction comes at a cost. Those taking aspirin were 30 percent more likely to have major intestinal bleeding. Most importantly, people who took aspirin (again those with no history of heart disease) had the same rate of death as those who took no aspirin.

So who should take aspirin?

It depends on what you and your doctor decide. While it's true that aspirin is very inexpensive, and low doses seem to be every bit as effective as higher doses, it can cause side effects like internal bleeding.

Research shows that 162 people need to take an aspirin every single day to prevent one nonfatal heart attack. However, two of these people will develop a serious bleeding problem.

Are the benefits worth it?

It depends on what you and your doctor decide.

We hear that aspirin can help alleviate the risk of cancer. Is that true?

This hasn't been quite as well-studied, but a recent review of nine major research studies shows that aspirin did not lead to a reduction in cancer deaths.

Do other pain relievers provide the same benefits as aspirin when it comes to heart disease, stroke or cancer?

It does not appear that other common pain relievers have this benefit. Some may actually cause harm. As we learned a few years ago, some pain relievers from the same family as aspirin, drugs such as Vioxx (rofecoxib) can actually cause heart problems rather than prevent them.

I think I should still take aspirin daily, but this latest news has me confused. What should I do?

Your primary care doctor can help you weigh your own risks and benefits.

If the doctor isn't up to date on the latest data, encourage him or her to read: www.uspreventive servicestaskforce.org/ uspstf/uspsasmi.htm.

OH, WILLOW TREE, HOW WE'VE LOVED THEE

These numbers reveal, among other things, that centuries before tiny plastic bottles of Bayer aspirin popped up in households around the world, man knew there was something special about the willow tree.

27

The percentage of regular aspirin users between the ages of 45 and 64 (Source: A report from the United States Agency for Healthcare Research and Quality in 2007)

370

Circa the year B.C. that Hippocrates, the father of modern medicine, is believed to have died. Hippocrates left records stating that a powder made from the bark and leaves of the willow tree could help heal headaches, pains and fevers.

1829

The year scientists discovered the compound salicin in willow plants

1853

The year French chemist Charles Frederic Gerhardt figured out a way to buffer aspirin, making it easier on the stomach for those who sought relief

1897

The year Felix Hoffman, building on the work of Gerhardt, synthesized acetylsalicylic acid at Bayer

80 billion

An estimate of the number of aspirin tablets taken annually.

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