But coffee lovers who have the type of gene that processes caffeine normally can drink as much coffee as they like without any added risk of a heart attack - or possibly even a much lower risk, according to a study in the March 7 issue of the Journal of the American Medical Association

Americans spend more than $17 billion a year on various forms of coffee, from cappuccinos to lattes, and average drinking about three cups a day.

Researchers at University of Toronto looked at a gene for an enzyme responsible for the metabolism of caffeine in the liver. One form of the enzyme metabolizes caffeine rapidly while another form metabolizes it slowly.

The study involved coffee-drinking habits of more than 4,000 Costa Ricans, half of whom had the genetic trait that made them "slow caffeine metabolizers." Those people who drank two or more cups of coffee a day were at least 36 percent more likely to have non-fatal heart attacks than those slow metabolizers who drank little or no coffee.

People under 50 with the same gene trait were up to four times more likely to have a heart attack than slow metabolizers in their age group who drank little or no coffee, and those drinking four or more cups had a 64 percent higher risk, researchers said.

People with the normal caffeine-metabolizing gene who drank up to three cups of coffee daily reduced their risk of a first heart attack by 22 percent, the study also showed.

Caffeine is thought to block the effects of a certain chemical that helps protect against tissue damage, said Ahmed El-Sohemy, a study co-author and nutrition scientist from the University of Toronto.

"Perhaps in the future we'll be making different dietary recommendations based on people's genetic makeup," said El-Sohemy, adding that people cannot tell if they're fast or slow caffeine metabolizers, even if an afternoon shot of coffee keeps them up all night. The only way to tell is through a genetic test, which is used for research purposes but is not available commercially.

Previous research linked coffee drinking to a higher risk of heart disease, while other studies found no connection. Some evidence shows caffeine cause short-term spikes in blood pressure, but a 2005 study found that coffee didn't appear to cause long-term hypertension, at least in women.

'Life is about moderation'

Dr. Roger Blumenthal, a cardiologist at Johns Hopkins Medical School who was not involved in the study, said that even if future research backs up the findings, he would still believe high blood pressure, cholesterol and smoking play a significantly more important role in heart attacks than caffeine.

The American Heart Association says coffee can trigger heart palpitations in caffeine-sensitive people. Caffeine, which also is found in colas, chocolate and other foods, stimulates the central nervous system, releases fatty acids into the body, and increases urination, which could lead to dehydration.

The association says that while studies on whether caffeine affects coronary heart disease are conflicting, drinking one to two cups a day doesn't seem harmful. However, caffeine-habituated individuals can experience "caffeine withdrawal" 12 to 24 hours after the last dose of caffeine. The most prominent symptom is headache, but other symptoms include anxiety, fatigue, drowsiness and depression.

"One good message that we can give people is that life is about moderation," said Dr. Nieca Goldberg, an association spokeswoman. "The study doesn't say you can't have caffeine, but drinking several cups of coffee daily is probably excessive for some people."

Source: Nubella News
Posted by: Steve Smith
Reference: Journal of the American Medical Association
Website: www.nubella.com

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