Drinking one or two cups of coffee raises the blood pressure by about 5 mm Hg. These effects are smaller in people who drink coffee regularly, which suggests that the effects may wear off with time.
Large scale epidemiological studies, in which the blood pressures of coffee drinkers have been compared with nondrinkers, have given rather inconsistent results. On average, regular coffee drinking may raise blood pressure a little, but not more than about 2 mm Hg.
Drinking coffee can also exacerbate the blood pressure-raising effect of other stressors. When taken with a cigarette, the blood pressure may increase by more than 10 mm Hg over the next hour or two, and coffee also exaggerates the response to mental stress.
Whatever its effects on blood pressure, the important thing about coffee drinking is that it has not been found to be associated with any excess mortality from heart attacks or strokes.
