Many things that we eat actually contain caffeine which is a mild stimulant. Food such as certain soft drinks, chocolate, tea and coffee all contain certain amount of caffeine. Consuming too much caffeine can result in us feeling jittery and nervous. More importantly, caffeine has also an effect of increasing our blood pressure. Two to three cups of coffee has enough caffeine to increase our systolic pressure 3 to 14 millimeters of mercury (mm Hg) and diastolic pressure 4 to 13 mm Hg in people without high blood pressure.

The exact way in which caffeine works to raise out blood pressure is unknown. Researchers have found that regular caffeine takers have a higher than average blood pressure relatively to non-caffeine takers. However, there are also researchers that have found that regular caffeine takers actually develop tolerance to the caffeine. Therefore, it does not have a long term effect on their blood pressure.

For non-regular consumers of caffeine, it can cause short-term but distinct increase in blood pressure. What exactly causes the distinct jump in the blood pressure is still unclear. Some researchers have suggested that caffeine actually has the effect of blocking the effects of adenosine. This is a hormones that works to keep vessels open. There is also a possibility that caffeine stimulate the adrenal gland to produce more cortisol and adrenaline which results in an increased blood pressure.

Interestingly, there is this particular study that has a huge sample size of 155,000 women and took over a long period of 12 years. This study found caffeinated cola may be associated with increased blood pressure while caffeinated coffee has no such effect. In fact, caffeinated coffee can actually lower the risk of getting high blood pressure.

Therefore, some doctors have told their patients to limit their daily caffeine intake to 200 milligrams as a precaution. This amount is equivalent to two 12-ounce cups of brewed coffee. However, the amount of caffeine present in different type of coffee differs by brands. Moreover, caffeine should be avoided before activities such as weightlifting, hard physical labour and exercise. This is because these activities will inevitably increase your blood pressure. The combination of caffeine and these activities will result in an even higher blood pressure.