Caffeine has long been accused of increasing blood pressure and possibly causing hypertension, but the comprehensive analysis of 16 control trials discussed in the article "Coffee and Cardiovascular Diseases" in Coffee: Emerging Health Effects and Disease Prevention found that while caffeine definitely elevates blood pressure, the caffeine in brewed coffee has a less pronounced effect.
"The increase in blood pressure produced by caffeine tablet ingestion was two to three times higher than that produced by regular coffee consumption despite equal mean doses of caffeine," the article reads.
Researchers suspect that something in coffee or the way it is prepared lessens the pressor effect of caffeine in its pure form.
"Taken together, these results show that coffee raises blood pressure acutely, but there is insufficient evidence to show that long-term coffee consumption causes hypertension," the authors conclude.
Coffee: Emerging Health Effects and Disease Prevention by Yi-Fang Chu