The aroma of freshly-brewed coffee may be one of the great comforters of the workaday world, but the actual contents of the pot represent a recipe for stress, high blood pressure and future heart disease. In a study of the effects of "moderate" coffee drinking throughout the day, researchers at Duke University have found that just a few extra cups could be enough to finish you off further down the line.
"The relevant message here is that the more caffeine you consume during the day in coffee, tea, or soft drinks, the higher your blood pressure is likely to be," says James Lane, associate research professor of psychiatry and lead author of the study. "Over many years, this increase in blood pressure may heighten your risk of suffering a heart attack or stroke, even if you don't have high blood pressure now."
Publishing their results in the May issue of Psychosomatic Medicine, the researchers describe the effects of coffee on nineteen habitual drinkers who wore "ambulatory" blood-pressure monitors as they went about their daily jobs. Four to five cups raised blood pressure an average of five points - an increase that remained elevated throughout the day - compared to stints when they consumed just one cup.
In what amounts to the first analysis of the effects of caffeine during normal working conditions, the results spell bad news for coffee addicts of all kinds. Regardless of mood or activity - whether sitting, standing or walking - caffeine acts directly on blood pressure.
Previously, scientists had wondered whether elevated blood pressure might not be a secondary consequence of stress or activity levels.
"You can measure how caffeine affects people in the laboratory, but that doesn't tell you what effects the drug has in the real world when people are exposed to normal stressors and activities," says Lane. "This strengthens the evidence that caffeine is working directly on blood pressure rather than through other mediating factors."
