The final verdict on coffee

If contradicting research has you wondering if coffee is healthy or harmful, the answer is simple: it depends.

A recent study showed a benefit from drinking java on a population level. But it's difficult to make individual recommendations for safe coffee consumption, said Dr. Ahmed El-Sohemy, a University of Toronto associate professor funded by the Canadian Institutes of Health Research who has studied caffeine and health.

El-Sohemy's research has showed that coffee could either lower or raise a person's risk of heart attack. That's because safe daily coffee intake is going to vary with the ability to process caffeine - and that changes from person to person. There's no easy way to tell how effectively your body deals with caffeine, and therefore how much of it is safe for you to drink, he said.

Because individual variations are hard to measure, it's difficult to confidently recommend a safe amount of coffee consumption because what might be dangerous for one person could have no effect on another, El-Sohemy said.

That's why numerous studies have associated coffee consumption with both an increased and a decreased risk for many chronic diseases, he said. Even for a single condition like heart disease, the findings have been inconsistent.

"You can sense the stimulating effects of caffeine when it binds to receptors in the nervous system," he explained. "You cannot feel how quickly your liver is breaking down caffeine in your body, and there are no other signs or symptoms that tell you whether or not caffeine can trigger a heart attack in you."

While the latest study, from the Universidad Autonoma de Madrid, did not prove that coffee is protective, its results strongly suggest that drinking coffee is not harmful to healthy individuals.

The researchers looked at thousands of healthy men and women from earlier studies and discovered that in the women, drinking two to three cups of coffee daily was associated with an 18 percent reduction in death from all causes, while four to five cups daily showed a risk reduction of 26 percent. The results in men were smaller and could have been due to chance, but followed similar trends.

Accounting for risk factors like weight, diet and smoking, the researchers found that people who drank coffee - caffeinated or decaf - were less likely to die than those who didn't, and their risk reduction could be attributed to a lower risk of dying of heart disease, despite previous studies showing an association between heart disease and caffeine consumption.

The Universidad Autonoma de Madrid study involved thousands of individuals - 84,214 women from Harvard Nurse's Health Study and 41,736 men from the companion study following male health professionals. A study of that size, which takes results from previous research and puts everyone into large groups, doesn't take individual variations into account, El-Sohemy said. If the majority of the people in the study happened to be fast metabolizers of caffeine, you'd predict that the results would show a protective effect, and vice versa.