Macau Cardiology Association
Does caffeine affect blood pressure? If so, how much is too much?

Caffeine’s effects on blood pressure have been widely studied, but all this research has not produced any widely accepted conclusions.

In a 2000 study of men, researchers investigated the effects of caffeine consumption on five groups – those with optimal blood pressure, normal pressure, high normal pressure, stage 1 high blood pressure, and men in treatment for high blood pressure at a hypertension clinic. Their blood pressure was measured after 20 minutes of rest and then again 45-60 minutes after ingesting 250 mg of caffeine. (A cup of brewed coffee contains approximately 100 mg of caffeine.)

The researchers found that caffeine did increase blood pressure on average, but not equally in all groups. While there was some increase in both systolic and diastolic blood pressure for men in the optimal and normal groups, the greatest increases were in the other three groups. In fact, those who were already in treatment for high blood pressure had the highest increases, almost 1.5 times greater than for those with optimal blood pressure. While the blood pressures of none of the men in the first two categories rose above 140/90 mm Hg (the hypertensive range), an increasing percentage in the other three categories did rise to that level: After caffeine ingestion, 19 percent of the high-normal, 15 percent of the stage 1, and 89 percent of the diagnosed hypertensive groups fell into the hypertensive range.

In a large study of women and caffeine, researchers found that the blood pressure readings of those who consumed little caffeine or a lot of caffeine were unaffected. Interestingly, those who consumed caffeinated colas, either diet or regular, did have modest increases in blood pressure. The increases were not significant enough that the researchers could recommend not drinking cola drinks.

Although caffeine may increase blood pressure temporarily, especially in people who are not habitual coffee or caffeinated-beverage drinkers, researchers have found no consistent evidence that average caffeine consumption (2-4 cups of brewed coffee per day) increases blood pressure to any significant degree for people who do not already have high blood pressure. The American Heart Association has concluded that there is no harm in the daily consumption of 1-2 cups of coffee or its equivalent.

There is no healthy level of high blood pressure. If your levels are above normal (less than 120 mm Hg systolic and less than 80 mm Hg diastolic), you should undertake lifestyle changes. Your doctor will decide whether to prescribe medications. Most people with high blood pressure require two or more medications to keep their blood pressure at goal.


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