Coffee heart risk is all in the genes

CHICAGO - The caffeine in coffee is unhealthy for some but beneficial to others, depending on a gene that determines how fast the chemical is metabolised, says a new study.

Since tests to determine which form of the gene one carries are not readily available and you cannot feel how fast your body is processing caffeine, the study's authors recommended reining in coffee consumption to no more than four cups a day.

Slightly more than half the 4024 study participants, who lived in Costa Rica between 1994 and 2004, had the slow version of the gene while the other half had the fast form. Half had had a non-fatal heart attack, and half had not.

"We found in individuals who had the slow version of this gene, as little as two cups of coffee a day is associated with an increased risk of heart disease," said study author Dr Ahmed El-Sohemy of the University of Toronto.

For those with the slow-acting gene, two to three cups of coffee a day increased their odds of a heart attack by 36 per cent, and four or more cups a day increased the risk by 64 per cent, the study said.

"For those who had the fast version of the gene, there was no increased risk, even with four or more cups a day," he said. "Surprisingly, what we found was that in individuals under 50 years of age who were fast metabolisers ... consumption of as little as one to three cups a day was associated with a lower risk of heart disease."

Those with the fast-acting gene who drank two to three cups of coffee a day had 22 per cent reduced odds of having a heart attack, but consuming four or more cups a day did not further lessen the risk, the study found.

"Initially we thought that individuals who had the slow version of this gene might drink less caffeine because it stays in their system longer, but what we found is that regardless of the version of the gene that the person had, it did not affect how much caffeine they consumed," Dr El-Sohemy said.

The liver enzyme cytochrome P450 1A2, which is responsible for metabolising caffeine, has a slow 1F version and a fast 1A version, said the study, which was published in this week's issue of the Journal of the American Medical Association.

"An individual cannot predict whether or not they have the slow or fast version of the gene, because although they can feel the effects of caffeine on the nervous system, they cannot feel the effects on their blood vessels," he said.

Previous studies have offered conflicting findings about the health effects of coffee, and Dr El-Sohemy noted other chemicals in coffee may play a role.

"Of all the studies that have been conducted to date that looked at the effects of either coffee or caffeine on heart disease, none of them have taken into account genetic differences in the ability to break down caffeine."

- REUTERS