Prospective epidemiological studies have given contradictory results. Results from the Multiple Risk Factor Intervention Trial (MRFIT) on 11,000 men for 6 years indicated a statistically significant inverse association between caffeine consumption and systolic or diastolic blood pressure (12). By contrast, a study of 1017 men for 33 years demonstrated an increased risk of hypertension associated with drinking 5 or more cups of coffee per day (13). However, this association was not significant.
In the light of the results of subsequent studies, the conclusions of Myers in his 1988 review are still valid. A more recent critical review of over 100 published studies concluded that coffee or caffeine may only be harmful to hypertension prone subjects and then only in large doses although the authors did not specify these doses (14).
Research into the effects of coffee drinking on blood pressure has continued and it can be concluded that coffee drinking is generally not considered to be an important risk factor for hypertension. The effect of caffeine from all drinks, including coffee, on blood pressure was found to be in the range of 2.0 – 2.4 mm Hg for systolic blood pressure and 0.73 – 0.80 for diastolic blood pressure (15,16,17).
Blood pressure levels return to baseline/control levels within a few hours following ingestion, with a fading of the mild hypertensive effect of caffeine taking place over a few days or weeks. A recently published meta-analysis of 16 studies reported that blood pressure elevations are larger with caffeine (systolic 4.16 mm Hg, diastolic 2.41 mm Hg) than with coffee (systolic 1.22 mm Hg, diastolic 0.49 mm Hg). This reflects that when ingested from coffee, caffeine has a small effect on blood pressure (17).
Further, Geliejnse et al in 2004 (18) reported that hypertension, the prevalence of which is increasing in Western societies, is mainly caused by being overweight, physical inactivity, high sodium intake, and low potassium intake with the impact of coffee being quite small by comparison.
Sri Jayawardenepura Kotte,
Hialeah, Florida, USA