Caffeine is known to cause a sudden and dramatic rise in blood pressure, even in those who don't have high blood pressure. The exact cause of this increase is still unknown. Everyone responds differently to caffeine, and research has shown that coffee can raise blood pressure up to three hours after consumption. However, if you drink it regularly, this effect tends to diminish.
According to cardiologist Dr. Seamus Whelton from Johns Hopkins Medicine, coffee and other caffeinated beverages cause the muscles in the arterial walls to contract and the diameter of the blood vessels to decrease, a process called vasoconstriction that increases blood pressure. But studies have also shown that the spike in blood pressure from coffee only lasts a few hours. Regular coffee drinkers are likely to develop tolerance.
In fact, one study showed that after two weeks of drinking coffee, the increase in blood pressure had disappeared. Whelton advises that if you are closely monitoring your blood pressure, you should avoid caffeine for at least half an hour before taking your readings. A recent review of clinical trials on the effect of long-term coffee consumption on blood pressure revealed that on average, coffee consumption was associated with 2.4 mm Hg higher systolic blood pressure and 1.2 mm Hg higher diastolic blood pressure. For each cup of coffee consumed, systolic pressure increased by 0.8 mm Hg and diastolic pressure by 0.5 mm Hg. The pressor effect of coffee consumption was more pronounced in studies with younger participants, those who administered more coffee, and those with a larger sample size. The relationship between coffee intake and blood pressure was independent of the mean age of study participants and study characteristics, such as preparation time.
The effect associated with coffee consumption in this analysis was substantially lower than that observed in a quantitative summary of trials that lasted two weeks, likely due to adaptation to the cardiovascular effects of coffee consumption. Hypertension, or high blood pressure, is a common condition where the blood pressure is consistently higher than normal. As coffee contains many different compounds besides caffeine, other compounds could be responsible for its effects on blood pressure. Previous research has shown that coffee temporarily increases blood pressure immediately after consumption, but the body quickly adapts to this effect. The same review suggested that the beneficial compounds of coffee, such as phenols, may have a protective effect. Some of these bioactive compounds present in coffee may offer health benefits like reducing oxidative stress and inflammation (2, 4).
Other studies have suggested that there may be a more persistent relationship between coffee consumption and the risk of developing high blood pressure over time. Data from cross-sectional studies suggest an inverse linear or U-shaped association of regular coffee consumption with BP in different populations. Some studies have even found that drinking four or more cups of coffee per day may protect against hypertension, particularly in women. If your blood pressure is consistently high for a period of time, your doctor may diagnose hypertension. If you are concerned about how your caffeine intake might affect your blood pressure levels, it is best to consult with your doctor for advice.