As the heart pumps blood through the body, force or pressure is applied to the artery walls. A blood pressure reading is the measurement of that force. Blood pressure can vary due to physical activity, emotional state and diet. Drinking black coffee, as long as it is not decaffeinated, can increase blood pressure.
Coffee and the Effect on Blood Pressure
In a study published in the November 1999 issue of "European Journal of Clinical Nutrition," researchers at the Institute of Biomedicine found that the intake of black coffee increased blood pressure. With most subjects, blood pressure rose with the initial consumption of coffee. Coffee had the strongest effect on those subjects who were prone to hypertension in the first place. However, researchers found that the regular consumption of black coffee had no long-lasting effects on blood pressure.
Caffeine: the Culprit
The American Dietetic Association considers black coffee a stimulant that has a slight impact on blood pressure and heart rate. The caffeine content in coffee is responsible for an increase in blood pressure. A single cup of coffee contains 95 mg of caffeine. In comparison, a caffeinated soda contains approximately 72 mg, and a small chocolate bar about 10 mg of caffeine.
Caffeine Increases Blood Pressure
Dr. Sheldon Sheps, a hypertension specialist with Mayo Clinic, reports that the amount of caffeine in two to three cups of coffee has the ability to raise the systolic -- top -- blood pressure number anywhere from 3 to 14 mmHg and the diastolic -- bottom -- blood pressure number from 4 to 13 mmHg. Caffeine blocks a hormone that is secreted to keep arteries widened. Also, caffeine causes the adrenal glands to release their stress hormones, cortisol and adrenaline, which cause an increase in blood pressure.
Limit your daily amount of caffeine to less than 200 mg -- about the amount of two 12-oz. cups of coffee. According to Mayo Clinic, the role caffeine plays in blood pressure is still debatable. Drinking black coffee or any other caffeinated beverage can temporarily cause a spike in blood pressure, but there is no long-term blood pressure increase. Once the caffeine is out of your system, blood pressure will return to the pre-coffee level.