Caffeine, a drug classified as a stimulant, produces physiological effects in the body by stimulating the release of the neurochemicals norepinephrine and epinephrine. Released during times of stress, these chemicals increase the rate of muscle contractions, make you more aware and fight off fatigue--the wanted effects of caffeine. Your heart also beats faster, which not only contributes to the increased awareness by increasing the amount of oxygen to the brain but also can cause a temporary increase in blood pressure.
High Blood Pressure
An increase in blood pressure is not the same as high blood pressure. The National Heart Lung and Blood Institute states a diagnosis of high blood pressure occurs when the systolic pressure measures 140 mmHg or greater or the diastolic blood pressure measures 90 mmHg or more. Since blood pressure fluctuates, consistent readings over these numbers receive a diagnosis of high blood pressure. Factors that contribute to high blood pressure include taking certain types of medications, smoking, alcohol consumption, weight and disease. Research published in "Hypertension" finds that caffeine increases blood pressure an average of ½ mmHg.
Factors
Although caffeine can cause a slight temporary increase in blood pressure, the National Heart Lung and Blood Institute does not list caffeine intake as a cause of high blood pressure. The effect of caffeine on your blood pressure depends upon several factors, including your age and your daily caffeine intake. Younger subjects have an increased risk of experiencing an increase in blood pressure, according to research published in "Hypertension." Drinking caffeine on a daily basis may produce tolerance, therefore reducing the effects of caffeine. In addition, some people are more sensitive to the effects of caffeine and this group of people may see an increase of 3 to 4 mmHg after drinking caffeine.
Suggested Consumption
Because caffeine may trigger a temporary increase in blood pressure, doctors suggest consuming caffeine in moderation. As of 2011 scientists continue to research the effects of caffeine on the cardiovascular system. "Hypertension" reports that consuming 2 to 4 cups of coffee per day, the average in the United States in 2004, does not cause a clinically significant increase in blood pressure.
Sources
If you currently suffer from high blood pressure, consult your doctor about your caffeine consumption. If you do need to limit your caffeine intake, you need to know what foods and beverages may contain caffeine. Most people know that coffee, tea and many sodas contain caffeine, but sweets, like chocolate, sports drinks and over-the-counter medications may also contain caffeine. An 8-oz. cup of coffee contains an average of 95 to 200mg of caffeine. Tea contains less, averaging 40 to 120mg per 8-oz. glass. A classic type of cola contains 35mg per 12 oz., sports drinks contain an average of 80mg, while a 1.5-oz. chocolate bar can contain between 9 and 31mg of caffeine.
References
- National Heart Lung and Blood Institute: High Blood Pressure
- "Scientific American"; How Does Caffeine Affect the Body?; Smatresk, N.; February 1999
- "Hypertension"; Effect of Caffeine on Blood Pressure Beyond the Laboratory; Myers, M.; 2004
- National Heart Lung and Blood Institute: Will Drinking a lot of Coffee Send your Blood Pressure Up?
- MayoClinic.com; Caffeine content for coffee, teas, soda and more; October 2009
