Nov. 18, 2002 -- Regardless of whether you take decaf or regular, getting your daily java fix may still give your nervous system a jolt. A new study suggests that it's not just the caffeine in coffee that gives your heart a buzz.
Researchers found that drinking a triple espresso, with or without caffeine, caused a blood pressure spike and an increase in nervous system activity among occasional coffee drinkers. Habitual coffee drinkers were immune to this immediate blood pressure-raising reaction, although their nervous system showed an increase in activity.
Activity in the nervous system is thought to play an important role in the regulation of blood pressure. Overstimulation of the system has been associated with high blood pressure.
Researchers say it's the first time such differences have been found in people's reaction to coffee. Coffee contains hundreds of substances, and the study authors say these findings suggest that something other than caffeine may be responsible for its effects on the heart.
"Until now we have attributed the cardiovascular effects of coffee to caffeine, but we found non-coffee drinkers given decaffeinated coffee also display these effects," says study author Roberto Corti, MD, a cardiologist at University Hospital in Zurich, Switzerland, in a news release. "This demonstrates how little we know about the effects of one of our most popular beverages and the most abundantly consumed stimulant worldwide."
Coffee's effects on the heart and cardiovascular system are controversial. Some studies have suggested that coffee drinking increases the risk of heart-related death, but others have disputed those results.
This study, published in today's rapid access issue of Circulation: Journal of the American Heart Association, looked at the effects of caffeine and coffee in 15 healthy volunteers, including six habitual coffee drinkers and nine occasional coffee drinkers. Researchers measured the participants' blood pressure, heart rate, and nervous system activity before, during, and after drinking a triple espresso with and without caffeine. They also took these measurements after an intravenous injection of the equivalent amount of caffeine or a placebo.
Sixty minutes after drinking the espresso, whether it had caffeine or not, occasional coffee drinkers had an increase in systolic blood pressure (the top number in a blood pressure reading). No change in blood pressure was found in the habitual coffee drinkers.
When they looked at nervous system activation, researchers found this activity rose after consumption of both caffeinated and decaffeinated coffee in both groups, despite the fact that blood pressure increases were found only among occasional coffee drinkers.
Corti says that regular coffee drinkers may build up a tolerance to the blood pressure-raising effects of coffee found in non-habitual drinkers. But the study suggests that tolerance to coffee does not seem to be related to caffeine because nervous system activity increased in both groups when they were given caffeine intravenously.
The study authors say more research is needed to determine how coffee affects the heart and cardiovascular system before recommendations can be made about whether people with high blood pressure should avoid decaffeinated coffee as well as regular.
Although the link between caffeine, coffee drinking, and heart disease is controversial, the American Heart Association says that moderate coffee drinking (one to two cups per day) does not seem harmful for most people.
Source: Circulation: Journal of the American Heart Association, Nov. 18, 2002, Rapid Access Publication • News release, American Heart Association.