Swiss scientists studying caffeine's effects in a small group of people report markedly elevated blood pressure and increased nervous system activity when occasional coffee drinkers drank a triple espresso, regardless of whether or not it contained caffeine.
Surprisingly, people who drank coffee on a regular basis showed increased stimulation of sympathetic nerve pathways but no increase in blood pressure.
This is the first time such disparities in reactions to coffee have been reported, says lead researcher Roberto Corti, M.D., a cardiologist at University Hospital in Zurich.
The results suggest that some unknown ingredient or ingredients in coffee not caffeine is responsible for cardiovascular activation, he explains. Coffee contains several hundred different substances.
"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," Corti says. "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 cardiovascular safety remains controversial," he says. "The possible health hazards have been related to its main ingredient caffeine."
The researchers measured blood pressure, heart rate and muscle sympathetic nervous system activity (MSA) in 15 healthy volunteers (ages 27 to 38) six habitual coffee drinkers and nine who either abstained or drank coffee only occasionally. Measurements were recorded before, during and after participants consumed a triple espresso, a decaf triple espresso or intravenous administration of the equivalent amount of caffeine, or a placebo. None of the subjects knew whether they
Contact: Carole Bullock
American Heart Association