Studies have shown that it is possible for caffeine to cause a short, but dramatic increase in your BP, even if you don't have high BP. A new meta-analysis shows that, among hypertensive individuals, caffeine intake of 1.5 – 2 cups produces an acute increase in BP, which lasts for at least three hours. However, present evidence does not support an association between longer-term coffee consumption and increased BP or increased risk of cardiovascular disease among patients with HBP.
In five trials, the administration of 200-300 mg caffeine (the content of 1.5-2 cups of filtered coffee) produced a mean increase of 8.2 mm Hg (95% confidence interval [IC] 6.2-10 mm Hg) in systolic BP and of 5.6 mm Hg (95% CI 4.2-6.9 mm Hg) in diastolic BP. The increase in BP was observed in the first hour after caffeine intake and lasted for at least three hours. In six trials on the longer-term effect (1 week) of coffee, there was no increase in BP when comparing caffeine versus placebo, coffee versus a caffeine-free diet, or coffee versus decaffeinated coffee.
“These results have clinical implications for the control of hypertensive patients. Because caffeine intake acutely increases blood pressure, hypertensive patients with uncontrolled blood pressure should avoid consuming large doses of caffeine. Also, the consumption of caffeine in the hours before measuring blood pressure may elevate the reading and give the erroneous impression that blood pressure is poorly controlled,” explains lead study author, Esther Lopez-Garcia, PhD, Department of Preventive Medicine and Public Health, Autonoma University of Madrid, Spain. “Finally, in well-controlled hypertensive patients, there is no evidence to justify avoidance of habitual caffeine consumption and healthcare providers should emphasize other lifestyle modifications, such as maintaining weight control, increasing physical activity, and stopping smoking.”