Caffeine is one of the most popular psychoactive stimulants in the world, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Caffeine is found naturally in cocoa, tea and coffee. Due to the fact that it has an effect on the central nervous system, it can cause anxiety, increased alertness and impact changes in mood, according to KidsHealth.org, it is recognized as a drug.
Theories
Even for people who don't have blood pressure problems, caffeine can cause a brief but dramatic increase in blood pressure, according to the Mayo Clinic's Sheldon G. Sheps, M.D., a hypertension specialist. No one knows for sure why caffeine has an effect on blood pressure, but it is believed that it may interfere with a hormone that is responsible for keeping arteries dilated. Another theory is that caffeine causes the adrenal glands to release additional adrenaline, which causes blood pressure to rise.
Hypertension
Experts understand that caffeine can cause a temporary rise in high blood pressure, but is not linked to hypertension, a chronic disease that causes high blood pressure and can lead to heart attack and stroke. The "Journal of the American Medical Association" published a study in 2005 to examine the association between caffeine intake and incident hypertension in women. Incident hypertension refers to high blood pressure with an identifiable cause. More than 150,000 women were followed over a 12-year period and the researchers found no link between caffeine consumption and hypertension.
Considerations
The rise in blood pressure is different depending on how you ingest caffeine, according to researchers from the department of human nutrition at Wageningen University in the Netherlands. In a review of 16 studies in 2005, the researchers found that in trials that looked at the combined affect of coffee and caffeine, blood pressure did in fact increase significantly. In trials that analyzed coffee and caffeine separately, blood pressure increased more significantly with caffeine, and only a negligible amount with coffee. The researchers concluded that when ingested though coffee, the effect of caffeine on blood pressure is small.
Amount
According to Dr. Sheps, it takes about 300 mg to 600 mg of caffeine, equivalent to two or three cups of coffee, at least seven cups of tea or two or three energy drinks, to raise systolic pressure between 3 and 14 millimeters and diastolic blood pressure 4 to 13 millimeters. Systolic blood pressure, which is the top number in a blood pressure reading, represents the force of blood in the arteries as the heart beats. Diastolic pressure, the bottom number in the reading, is the force of blood in the arteries when the heart is at rest. Your diastolic reading does not need to change for you to have high blood pressure. A normal blood pressure reading is 120 over 80. When it hits 140 over 90, it's considered high.
References
- "Journal of the American Medical Association"; Habitual Caffeine Intake and the Risk of Hypertension in Women; Wolfgang C. Winkelmayer, MD, et. al; 2005
- "Journal of Hypertension"; Blood Pressure Response to Chronic Intake of Coffee; Noordzij M.; et al. May 2005
- MayoClinic.com: Caffeine: How Does it Affect Blood Pressure?; November 2009
- National Heart, Lung and Blood Institute? What are High Blood Pressure and Prehypertension?
- MedlinePlus: High Blood Pressure
- MayoClinic.com: Caffeine Content for Coffee, Tea, Soda and More; October 2009
