Caffeine's Effect on Blood Pressure

May 17, 2002 -- The caffeine jolt of a java fix may cause a jump in blood pressure -- a particular problem in people who already have high blood pressure. But don't put your coffee cup down just yet. Researchers say the jury's still out on the effects on caffeine on your heart.

This new study was presented today at the annual scientific meeting of the American Society of Hypertension in New York City.

Although there has been a lot of recent interest in studying how caffeine may affect the heart and blood pressure, the authors say it's the first time an effect of caffeine has been found on the stiffness of arteries, an indicator of heart function.

In the study, caffeine quickly increased the stiffness of the large arteries in people with high blood pressure, said study author Charalambos Vlachopoulos, MD, of the department of cardiology at Athens Medical School in Greece, at a news conference.

Vlachopoulos and colleagues tested the effects of caffeine on the major arteries of 10 people who were being treated for high blood pressure and were an average of 62 years old. On alternating days, the participants were given either a pill containing 250 mg of caffeine (the equivalent of 2-3 cups of coffee) or a placebo.

Thirty minutes after the caffeine was given, there was a big jump in the stiffness of their arteries, said Vlachopoulos. The effect peaked after 60 minutes and remained significant for at least three hours.

This led to an 11 point jump in systolic blood pressure -- the top number -- and an 8 point jump in diastolic blood pressure -- the bottom number.

Researchers say this finding is only preliminary and more research is needed to determine exactly how caffeine intake may influence blood pressure as well as determine who's at risk.

Alice H. Lichtenstein, DSc, vice-chairwoman of the American Heart Association's nutrition committee, agrees this finding merits further study, but she stresses that there isn't any real cause for concern based on this very small study.

"It's hard to superimpose this scenario on everyday life," Lichtenstein tells WebMD. "It's very likely that different people respond differently to coffee. People who are habituated to drinking large amounts do not respond in the same way as people who do not drink coffee."

In addition, she says people who consume coffee also consume other things, such as cream, sugar, or other foods, that may dilute this effect.

"It's impossible to feel your own blood pressure going up after a cup of coffee," says Lichtenstein, who is also a professor of nutrition at Tufts University. She suggests that if someone is concerned about how coffee and caffeine may be affecting their blood pressure, they should try having a cup of coffee before their next doctor's appointment and blood pressure check and then discuss the effects with their doctor.