Coffee Jitters? Don't Blame the Caffeine

Study suggests ingredient other than caffeine may cause blood pressure spikes

MONDAY, Nov. 18, 2002 (HealthDayNews) -- There's good news for regular coffee drinkers who are in good health: It's probably not going to raise your blood pressure.

However, there's not-so-good news for those who don't have a coffee habit: Drink it, and even decaf can boost your blood pressure.

These findings come from a Swiss study, reported in today's online issue of Circulation. They add to the growing, often controversial, body of research about the effect of coffee on your health.

Dr. Roberto Corti, a cardiologist at University Hospital Zurich in Zurich, Switzerland, and his team evaluated 15 healthy people: six regular coffee drinkers and nine "non-habitual" drinkers who avoid coffee and caffeinated colas.

They gave each a triple espresso, a decaf triple espresso, an intravenous dose of caffeine and an intravenous dose of saline. They measured their blood pressure and sympathetic nervous system activity before and after. The sympathetic nervous system plays an important role in blood pressure regulation and its overactivation has been linked with high blood pressure.

The non-habitual coffee drinkers showed an increase in sympathetic nervous system activity and blood pressure after IV coffee, coffee and even decaf. Their systolic blood pressure (the top number of the reading) increased about 12 millimeters of mercury and their diastolic (the bottom number) increased about 7 millimeters an hour after the consumption or administration of the coffee.

Regular coffee drinkers also had an increase in their sympathetic nervous system activity, but their blood pressure did not increase, probably due to tolerance, the researchers say, but perhaps not to caffeine.

As the results with the non-habitual drinkers who got a rise in blood pressure even with the decaf coffee suggest, it might not be the caffeine that's to blame for activating the cardiovascular system, the researchers say.

"The only conclusion you can derive from our study is that caffeine is not the only [substance] responsible for the cardiovascular effects of coffee," Corti says. There's not a possibility that the decaf coffee really contained caffeine, since the researchers also measured blood levels of caffeine and found no increase in people after they drank or were administered the decaf preparations.

"Two findings were very surprising," Corti says. "The first, that habitual coffee drinkers don't have an increase in blood pressure despite activation of the sympathetic nervous system, and the second that in non-habitual coffee drinkers both 'regular' coffee and decaffeinated coffee led to an activation of the sympathetic nervous system and [a rise in] blood pressure."

Corti plans to continue his research, next evaluating what happens when people drink coffee under stressed conditions rather than at rest, as in his study. He also hopes to identify the ingredient responsible for the cardiovascular activation, perhaps paving the way for the development of new forms of coffee that would be lacking the undesirable stimulants.

Another expert, Dr. Robert H. Eckel, calls the study interesting.

"The idea that coffee may contain an ingredient we don't know about [that impacts its cardiovascular effect] is of interest," says Eckel, a professor of medicine at the University of Colorado Health Sciences Center in Denver and chairman of the American Heart Association's Council on Nutrition, Physical Activity and Metabolism.

The fact that regular coffee drinkers didn't get a boost in pressure makes sense, he says: "Tolerance to coffee is real."

However, Eckel suggests the researchers should also look at people older than those in the current study, who range from age 27 to 38, and that they should evaluate a bigger sample.

Until more research is in, Corti says healthy coffee drinkers without a family history of high blood pressure are probably not increasing the likelihood of cardiovascular disease by continuing to drink coffee.

"In others words, healthy people that have a regular coffee intake should not be concerned," Corti says.

On the other hand, he adds, "occasional coffee drinking seems to have an important cardiovascular stimulatory effect and can acutely increase blood pressure."

"At this point in time, I would not change the recommendations" for coffee drinkers, Eckel adds. While certain people, such as those with high blood pressure and ulcers, are usually advised to stay away from coffee, for healthy people the beverage is probably acceptable, he says.

What To Do

For more information on blood pressure and keeping it under control, see Blood or National Heart, Lung, and Blood Institute.

SOURCES: Roberto Corti, M.D., cardiologist, University Hospital Zurich, Zurich, Switzerland; Robert H. Eckel, M.D., professor, medicine, University of Colorado Health Sciences Center, Denver, and chairman, American Heart Association Council on Nutrition, Physical Activity and Metabolism; Nov. 18, 2002, Circulation
Consumer News