What are common sources of caffeine, Caffeine is a mild stimulant found in tea, chocolate, coffee and also in many soft drinks. If we take too much caffeine it can cause nervousness and jitters and palpitations. It may also increase your blood pressure. The amount of caffeine in two to three cups of coffee can raise systolic pressure 3 to 14 millimeters of mercury (mm Hg) and diastolic pressure 4 to 13 mm Hg in individuals without high blood pressure.

Individuals who don't take caffeine on a regularly, caffeine can cause a temporary but sharp rise in blood pressure. Exactly what causes this spike in blood pressure is unknown. Some researchers suggest that caffeine narrows blood vessels by blocking the effects of adenosine, a hormone that helps keep them widened. Caffeine may also stimulate the adrenal gland to release more cortisol and adrenaline, which cause your blood pressure to raise.

Some studies have found that individuals who regularly drink caffeine have a higher average blood pressure than those who drink none. Other research has suggested that regular takers of caffeine develop a tolerance to it — and as a result, caffeine doesn't have a long-term effect on their blood pressure.

In another study, a 12-year study of 155,000 women found that drinking caffeinated cola may be associated with an increased risk of high blood pressure. However, the same causal relationship was not found with caffeinated coffee. In fact, the study suggested that women who drink caffeinated coffee may actually have a reduced risk of high blood pressure.

Similarly, a recent (2007) study shows that women who drinks 6 cups of caffeinated coffee a day have lower risks of high blood pressure than do women who drink three or fewer cups daily. The same study found that men and women who never drink coffee also have lower risks of high blood pressure.

As a precaution, some doctors recommend limiting caffeine to 200 milligrams a day — about the same amount as in two 12-ounce cups of brewed coffee. Keep in mind that the amount of caffeine in coffee and soft drinks varies by brand. Also, avoid caffeine right before activities that naturally increase your blood pressure, such as weightlifting or hard physical labor exercise.

To observe if caffeine might be raising your blood pressure, check your blood pressure within 30 minutes of drinking a cup of coffee or another caffeinated beverage you regularly take. If your blood pressure increases by five to 10 points, you may be sensitive to the blood-pressure-raising effects of caffeine. If you plan to reduce your intake of caffeine, do so gradually over several days to a week to avoid withdrawal symptoms like headaches.

Product / Caffeine
(in milligrams)
 
Coffee (6 oz. cup)
Drip 175
Percolated 132
Instant regular 64
Decaffeinated 3
Cola Drinks (12 oz)
Coca-Cola Classic  46
Coca-Cola, new 46
Coke Free 0
Pepsi 43
Pepsi Free 0-2
Carob (chocolate substitute) 0
Nonprescription drugs 
Caffedrine capsules (each)  100
NoDoz tablets (each)  100
Weight-control aids
Dexatrim (daily dose) 200 
Dietac (daily dose)  200
Prolamine (daily dose)
Dr. Pepper 38 
Mountain Dew 52
Tab 50
Jolt 71
44 oz. cup of Coke/Pepsi  169/158
Tea (5 min. brew, 6 oz) 24-60
Cocoa and chocolate
Cocoa beverage (water mix, 6 oz) 18
Milk chocolate candy bar (8 oz) 48
Baking chocolate (1 oz) 35
White chocolate 0

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