Mar 8/06
by Nicolle Wahl

If your day isn’t complete without four jumbo lattes with extra foam, the effect that caffeine has on your ticker could depend on your DNA.

A new study led by researchers at the University of Toronto suggests that people with a certain version of a gene that allows caffeine to linger in their bodies may be at higher risk for a heart attack than people whose genes remove caffeine from their body quickly. But since no commercial test exists to tell coffee drinkers what version of the gene they carry, the researchers recommend limiting caffeine consumption to the equivalent of two cups of coffee per day.

“Of all the studies that have been conducted to date that looked at the effect of coffee or caffeine on heart disease, none of them have taken into account genetic differences and the ability to break down caffeine,” says study author Ahmed El-Sohemy, an assistant professor in the Department of Nutritional Sciences of the University of Toronto and Canada Research Chair in nutrigenomics.

The findings appear in the March 8 issue of the Journal of the American Medical Association and also involved researchers from Harvard University and the University of Costa Rica.

The researchers performed genetic tests on 2,000 patients who had suffered heart attacks and compared the results to 2,000 healthy subjects, all of them from the coffee-rich country of Costa Rica. They were looking for a specific DNA sequence of a gene called CYP1A2, which is known to break down caffeine. All people have two copies of the gene, but people with mutations in one or both genes will break down caffeine slowly. Those with the genetic defect process caffeine up to four times more slowly than people with a normal gene.

“We found that in individuals who had the slow version of this gene, as little as two cups of coffee a day was associated with an increased risk of heart disease,” El-Sohemy says. “For those who have the fast version of the gene, there was no increased risk, even with four or more cups a day.”

The effects were strongest among people under the age of 50. “Surprisingly, what we found was that those under 50 years of age who had fast versions of this gene, the consumption of as little as one to three cups a day was associated with a lower risk of heart disease,” El-Sohemy says. The findings suggest that for this group, a small amount of daily coffee may in fact have a protective effect.

Without genetic testing, it’s not possible for individuals to know whether they have the fast or the slow gene—the nervous system reaction that produces the “buzz” from coffee is not related to how the CYP1A2 gene metabolizes caffeine.