Gene Can Determine Heart Attack Risk for Coffee Drinkers - Caffeine May Increase Risk and Cause Decreased Blood Flow During Exercise

March 7th 2006

2 cups maximum

A new study indicates that there may be genetic link between caffeine and heart attacks. According to researchers from the University of Toronto, an enzyme called cytochrome P450 1A2 (CYP1A2) metabolizes caffeine in the liver. A gene variation for this enzyme can slow or quicken caffeine metabolism.

The Toronto team wanted to study whether this gene variation may be associated with an increased risk of non-fatal heart attacks. They compared 2,014 patients with a first nonfatal heart attack with 2,014 healthy people.

Their findings showed that participants with the slow-metabolism variation of the gene, who drank two to three cups of coffee a day, had a 36-percent increased risk of having a heart attack.

The more coffee the slow-gene participant drank, the more the risk factor rose. They found that those who drank four or more cups had a 64-percent increased risk. On the other hand, those participants that had the rapid-metabolism gene variation, who had the same amount of coffee actually reduced their odds of heart attack by 22 percent and 1-percent respectively.

The study shows that if you limit your coffee intake to 2 cups or less per day, your increased risk of a nonfatal heart attack will be raised only slightly. This research was published in the March 8th issue of the Journal of the American Medical Association.

In a related story, back in January a Zurich team found that coffee may impair peak heart performance. The Zurich researchers found that in healthy volunteers, the equivalent of two cups of coffee reduced the body's ability to boost blood flow to the heart muscle in response to exercise.

Usually, the myocardial blood flow needs to increase in order to match the increased need for oxygen during exercise. Philipp A. Kaufmann, M.D., said “We found that caffeine may adversely affect this mechanism. It partly blunts the needed increase in flow.” Philip is a doctor at the University Hospital Zurich and Center for Integrative Human Physiology CIHP in Zurich.

The researchers say the blood flow in the heart muscle was not affected at rest. However, the blood flow measurements taken immediately after exercise were significantly lower after the participants had taken the caffeine. This study was published in the January 17th issue of the Journal of the American College of Cardiology.