Is Coffee Good For You? It Depends On Your Genes

Researchers at the University of Toronto, Harvard University and the University of Costa Rica are aware of all the other studies on coffee and heart attacks.

"None of them have taken into account genetic differences in the ability to break down caffeine," said Ahmed El-Sohemy, of the University of Toronto.

The study compared the genes and coffee drinking habits of about 2,000 people who'd had heart attacks and another 2,000 who had not. They found about half the people in the study had a slow version of the gene that breaks down caffeine. The rest had a fast version.

"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," El-Sohemy said.

Plus, those with the fast version of the gene had no increased risk, even with four or more cups a day. The effects were strongest among people under 50 years of age. In that same age group, those with the fast version of the gene experienced the strongest positive effects.

"Consumption of as little as one to three cups a day was associated with a lower risk of heart disease," El-Sohemy said.

For those people, coffee may be good for the heart.

"We are approaching the era of personalized dietary advice," El-Sohemy said.

There is no commercial test available to tell which version of the gene you have, so doctors recommend drinking no more than four cups of coffee a day.