Caffeine, classified as a central nervous system stimulant, remains the most widely consumed pharmacological agent in the world in 2011. The U.S. Food and Drug Administration reports that 80 percent of adults in the United States consume caffeine on a daily basis at an average of 200mg per day, which represents the amount contained in two 5-oz. servings of coffee. Along with the wanted effect of alertness, caffeine may produce unwanted effects like an increase in blood pressure.
Blood Pressure
Blood pressure is the measure of the force of blood against the walls of the blood vessels. Doctors determine blood pressure with a combination of two measurements: the systolic pressure and the diastolic pressure. The systolic pressure measures the force of the blood when the heart contracts and the diastolic pressure measures the force of the blood when the heart relaxes. Many factors affect blood pressure including smoking, alcohol use, exercise and diet. Excessive salt intake increases blood pressure by increasing blood volume. The way caffeine increases blood pressure is much more complicated.
Vascular Adenosine Receptors
Your brain produces a compound known as adenosine, classified as a nucleoside. Adenosine binds to adenosine receptors throughout the body, which slows down nerve cells, causes drowsiness and makes blood vessels dilate. Caffeine is classified as an adenosine receptor antagonist, which means that it binds to the adenosine receptors in the blood vessels, therefore blocking adenosine from binding. This is how caffeine fights drowsiness. Constricting the blood vessels, especially in the head and neck region, allows caffeine to reduce the pain of headaches. But the blood vessel constriction also causes a slight increase in blood pressure.
Factors
Although caffeine has the ability to increase blood pressure, the effects vary from person to person. Research studies, such as the one published in the 1999 issue of "Hypertension," have found that younger subjects experience a more dramatic increase in blood pressure than older subjects. In addition, the amount of caffeine you consume each day makes a difference. If you regularly consume caffeine, your body builds up a tolerance, therefore reducing the effects of the caffeine, including the increase in blood pressure. Some people, however, only develop a partial tolerance to caffeine, so even with regular consumption, you may still experience small blood pressure increases. The amount of caffeine you consume also affects your blood pressure.
Outcome
Despite the fact that caffeine can trigger an increase in blood pressure in some people, the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure does not suggest restricting caffeine intake as a lifestyle change to lower blood pressure, according to information provided in a 2004 issue of "Hypertension." In fact, caffeine, when consumed in moderation, can provide some health benefits, while the negative effects occur with excessive consumption, according to information in the Harvard Health Publications.
References
- U.S. Food and Drug Administration; Medicines in my Home: Caffeine and Your Body; 2007
- Harvard Health Publications; Coffee Health Risks: For the moderate drinker, coffee is safe says Harvard Women's Health Watch; August 2004
- "Hypertension"; Blood Pressure Response to Caffeine Shows Incomplete Tolerance After Short-Term Regular Consumption; Lovallo, W. et al.; 2004
- "Hypertension"; The Effect of Chronic Coffee Drinking on Blood Pressure; Jee, S., et al.; 1999
- "Hypertension"; Effects of Caffeine on Blood Pressure Beyond the Laboratory; Myers, M.; 2004
