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Back to Cardiology Articles
Wednesday 15th March, 2006
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Persons with a genetic variation may have slower caffeine
metabolism according to a study in the March 8 issue of JAMA.
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Individuals who have a genetic variation associated with
slower caffeine metabolism appear to have an increased risk of
non-fatal heart attack associated with higher amounts of coffee
intake, according to a study in the March 8 issue of JAMA.
Studies examining the association between coffee consumption
and risk of myocardial infarction (MI ? heart attack) have been
inconclusive. Coffee is a major source of caffeine, which is the
most widely consumed stimulant in the world and has been
implicated in the development of cardiovascular diseases such as
heart attack, according to background information in the
article. However, coffee contains a number of other chemicals
that have variable effects on the cardiovascular system. It is
not clear whether caffeine alone affects the risk of heart
attack or whether other chemicals found in coffee may be
responsible. Caffeine is metabolized primarily by the enzyme
cytochrome P450 1A2 (CYP1A2) in the liver. Variations of the
gene for this enzyme can slow or quicken caffeine metabolism.
Carriers of the gene variant CYP1A2*1F allele are "slow"
caffeine metabolizers, while individuals with the gene variant
CYP1A2*1A allele are "rapid" caffeine metabolizers.
Ahmed El-Sohemy, Ph.D., of the University of Toronto, and
colleagues conducted a study to determine whether gene
variations of CYP1A2 modifies the association between
consumption of caffeinated coffee and risk of nonfatal heart
attack. The study included 2,014 case patients with a first
acute nonfatal heart attack and 2,014 controls, living in Costa
Rica between 1994 and 2004. The genotypes of the participants
were determined. A food frequency questionnaire was used to
assess the intake of caffeinated coffee.
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Fifty-five percent of cases (n = 1,114) and 54 percent of
controls (n = 1,082) were carriers of the slow *1F allele. For
carriers of the slow *1F allele, those who drank 2 to 3 cups of
coffee a day had a 36 percent increased odds of heart attack;
those who drank 4 or more cups per day had a 64 percent
increased odds of heart attack. Corresponding consumption for
individuals with the rapid *1A/*1A genotype resulted in the
reduced odds of heart attack by 22 percent and 1 percent,
respectively.
Among the slow metabolizers, younger individuals
showed an increased risk. The risk associated with drinking 4
cups/d or more compared with less than 1 cup/d increased from
2-fold for individuals younger than 59 years to more than 4-fold
for those younger than 50 years. Among the fast metabolizers who
were younger than 59 years of age, those who drank 1 cup/d or 2
to 3 cups per day had a reduced odds of a heart attack by 52
percent and 43 percent, respectively.
"In summary, consistent with most case-control
studies, we found that increased coffee intake is associated
with an increased risk of nonfatal MI. The association between
coffee and MI was found only among individuals with the slow
CYP1A2*1F allele, which impairs caffeine metabolism, suggesting
that caffeine plays a role in the association," the authors
conclude.
Source
JAMA. 2006;295:1135-1141.
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