8 March 2006

Wrong Genes And Coffee's A Heart Stopper

by Kate Melville

A cup of coffee in the morning may seem innocuous enough, but new research shows that coffee may put some people at risk of suffering a myocardial infarction (heart attack). While a link has been suspected for some time, research into the connection between coffee consumption and cardiovascular diseases such as myocardial infarction (MI) has so far drawn a blank. This is partly because caffeine also contains a number of other chemicals that may work independently, or in combination with caffeine, to produce an adverse affect on health.

But since coffee is the most widely consumed stimulant in the world and second only to oil in the global commerce stakes, it would be helpful to know whether caffeine is indeed responsible for an adverse effect.

After all, a few cups of Joe aren't worth your health are they (well, actually�)? As it turns out, some new findings concerning caffeine and its effects on human metabolism have just been made public by Ahmed El-Sohemy, of the University of Toronto.

Caffeine is predominantly metabolized in the liver by an enzyme called cytochrome P450 1A2 (CYP1A2), but according to Sohemy's study, published in the Journal of the American Medical Association, a genetic variation of this enzyme dictates the rate at which caffeine is metabolized.

El-Sohemy's team set about devising an experiment to discover whether variations of the CYP1A2 enzyme are linked to a greater risk of non-fatal MI. Two-thousand patients with a first acute non-fatal heart attack and an equal number of controls were scrutinized between 1994 and 2004. Determining the subjects' genotypes was necessary for the experiment, as was a food frequency questionnaire used to track the quantities of caffeinated coffee consumed by the participants.

The team found that 55 percent of MI cases and 54 percent of controls were carriers of the gene variant CYP1A2*1F allele, which means that they metabolize caffeine very slowly. The team claims that a slow metabolizer of caffeine who drinks 2-3 cups of coffee in a day has a 36 percent increased risk of a non-fatal MI. But the risk of an MI in those who drank 4 or more cups of coffee a day shot up to a staggering 64 percent.

Younger individuals in the slow genotype group showed that they were at even greater risk. For those younger than 59 who drank 4 or more cups of coffee the risk increased 2-fold, while for those under the age of fifty, the risk increased 4-fold.

"We found that increased coffee intake is associated with an increased risk of non-fatal MI. The association between coffee and MI was found only among individuals with the slow CYP1A2*1F allele, which impairs caffeine metabolism, suggesting that caffeine plays a role in the association," the authors concluded.

Source: University of Toronto