There
have been several clinical studies into the effects of coffee on blood pressure, these studies have shown rather inconsistent results. Drinking
a regular amount of coffee, say 2 - 4 cups a day, may raise blood pressure slightly. Respected agencies including the Food and Drug Administration,
the National Academy of Sciences and the U.S. Surgeon General’s office have stated that caffeine carries no health risks.
Drinking one or two cups of coffee raises the blood pressure by about 5 mm Hg. Any such effects are not permanent, passing within a few hours. This is because, unlike alcohol or smoking, caffeine doesn't accumulate in the body. Some people who coffee regularly can develop a tolerance to it, such that they no longer notice any effect even after several cups of coffee.
If you have high blood pressure and drink a lot of coffee, the results of studies suggest that if you stop drinking coffee (or possibly switch to decaffeinated) you may experience a slight fall of your blood pressure, but don’t expect a dramatic change.
Whatever its effects on blood pressure, the important thing about coffee drinking is that it has not been found to be associated with any increased mortality from heart attacks or strokes.For most people moderate drinking of coffee (4 - 5 cups per day) is considered perfectly safe. Thats about 400mg of caffeine. Pregnant women should stay below 300mg of caffeine per day. (Remember that caffeine can be found in other products like Tea, Cola, Sports Energy Drinks and Chocoalte.)