After years of uncertainty about whether drinking coffee is unhealthy, a new study suggests the answer may lie in one’s genes.
The report says the risk of suffering a nonfatal heart attack increases with coffee consumption in people who have a gene variation linked to slower caffeine metabolism.
In contrast, higher coffee consumption can reduce the risk of heart attack in those with a gene variation associated with faster caffeine metabolism, according to the study in yesterday’s issue of Journal of the American Medical Association.
“Our findings indicate that people who metabolize caffeine more slowly are not getting rid of it fast enough. They are not getting rid of the caffeine before it can cause harm,” said Ahmed El-Sohemy of the Department of Nutritional Sciences at the University of Toronto and the study’s lead author.
The study, which included researchers from the Harvard School of Public Health and the University of Costa Rica, analyzed more than 4,000 people — average age 58 — who lived in Costa Rica between 1994 and 2004. Half of the subjects were men and women who had survived one acute heart attack. The other half were healthy control subjects who were matched in terms of age, sex and area of residence.
In the report, Mr. El-Sohemy explained that studies examining the association between coffee consumption and heart attack risk have been “inconclusive.”
While caffeine is known to increase the risk for cardiovascular disorders, he said, “Coffee contains other chemicals that may have adverse effects on the cardiovascular system.”
To determine whether that is the case, the researchers focused on an enzyme in the liver — known as CYP1A2 — that is the body’s primary metabolizer of caffeine. Because genetic variations of this enzyme can either slow or quicken caffeine metabolism, the researchers wanted to determine “whether CYP1A2 genotype variations modify the association between coffee consumption” and heart attack risk.
Testing determined that 55 percent of those who had suffered a heart attack and 54 percent in the control group carried the slow-metabolizing CYP1A2 gene.
The study found that slow metabolizers who drank two to three cups of coffee a day increased their risk of a heart attack by 36 percent. The risk soared to 64 percent in those who drank four or more cups of coffee daily.
But fast metabolizers who drank two to three cups of coffee a day reduced their risk of heart attack by 22 percent. Fast metabolizers who drank four or more cups of coffee daily also decreased their heart attack risk, but by less than 1 percent.
Mr. El-Sohemy acknowledged that the technology used to determine CYP1A2 genotypes in the study is complex and “is not commercially available.”
Despite the study results, Lars Ators, spokesman for Folgers Coffee, the nation’s market leader, said “it is premature to consider any changes [in coffee consumption habits] at this time. Most studies have concluded coffee consumption does not increase overall risk for cardiovascular disease or mortality.”