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It's Not Just the Caffeine That Gives You a Jolt

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.

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