Coffee good or bad for you? It depends on your genes!

According to a new study, depending on your genes, the caffeine in coffee is either good for you or bad for you.

The link between coffee intake and the risk of heart attacks is a controversial issue.

Scientists know that coffee, a major source of caffeine, is metabolized by the enzyme, cytochrome P450 1A2, and some individuals who have that particular gene are "rapid" caffeine metabolizers, whereas those with a different variation of the gene are "slow" caffeine metabolizers.

The researchers wanted to find out if that particular gene had any implications for the risk of heart attacks.

The study done over a ten year period from 1994 to 2004, involved over 4000 people living in the coffee lovers haven, Costa Rica.

Just over half the group members had the slow version of the gene while the other half had the fast form.

Half the group had had a nonfatal heart attack, and half had not.

Dr. Ahmed El-Sohemy of the University of Toronto, one of the authors of the study, says they found in individuals who had the slow version of this gene, two to three cups of coffee a day increased their odds of a heart attack by 36 percent, and four or more cups a day increased the risk by 64 percent.

While for those with the fast version of the gene, there was no increased risk, even with four or more cups a day, says Dr. El-Sohemy.

Apparently one surprisingly discovery was that for those under 50 years of age who were fast metabolizers, as little as one to three cups a day was associated with a lower risk of heart disease.

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

El-Sohemy says that though they thought at first individuals who had the slow version of the gene might drink less caffeine because it stays in their system longer, they found in fact that regardless of the version of the gene that the person had, it did not affect how much caffeine they consumed.

Cytochrome P450 1A2, has a slow 1F version and a fast 1A version, and people cannot predict which they have because although the effects of caffeine on the nervous system are noticeable, the effects on their blood vessels are not.

A variety of studies present conflicting advice about the health effects of coffee, and El-Sohemy does say other chemicals in coffee may be implicated.

The study's authors say as tests to determine which form of the gene a person carries are not readily available, restricting coffee consumption to no more than four cups a day is advisable.

The study is published in the Journal of the American Medical Association.