How Does Caffeine Affect Blood Pressure?

The link between caffeine and blood pressure has been a particular area of interest and controversy for more than 70 years. Coffee, the most controversial source of caffeine, has been a staple in the diet of mankind for hundreds, if not thousands of years. The dependency on coffee, however, is a new phenomenon as work, home and night life have begun to push on the envelope of proper time management and allocation. Additionally, the sale of coffee has become a big business with newer and larger franchises opening every day.

About

Coffee is often mentioned first when discussing caffeine, but it is important to know that caffeine is in many other commonly consumed foods and drinks. Caffeine is a component of teas including black, green and white tea, chocolate, sodas, concentrated caffeine supplements and caffeine-based drinks. Caffeine appears to temporarily increase blood pressure, although its long-term contribution to blood pressure remains controversial. Research of caffeine has identified at least three different mechanisms by which blood pressure is increased. These reactions are natural to the body in cases of low blood pressure, but appear to be activated in the presence of caffeine.

Renin

Renin is a hormone naturally produced by the kidneys in response to an awareness that the volume of blood flowing through the kidneys has lessened and BP has dropped. Renin sets off a cascade of events that leads to the constriction of the blood vessels and a resultant rise of blood pressure. A 1996 "Journal of Cardiovascular Pharmacology" found that the central nervous system of rats can naturally override the effects of renin release from the kidney when regulating natural BP fluxes. The study concluded, however, that caffeine has the ability to disable the effects of the CNS, thereby increasing renin release.

Blood Vessel Changes

Blood vessels have the ability to dilate and constrict depending on the body's requirement of blood flow to a particular area as well as the overall quantity of blood circulating in the body. When the concentration of the fluid or plasma of the blood is less than what is normal for the body, the body will reduce the diameter of the blood vessels through blood vessel constriction so that overall flow and pressure can be maintained. The effects of caffeinated expresso versus decaffeinated expresso on the ability of blood vessels to dilate was studied and published in a 2010 "European Journal of Clinical Nutrition" article. Researchers concluded that the ingestion of caffeine had unfavorable cardiovascular and BP effects, namely inhibiting blood vessel dilation.

Stress Hormone Production

Caffeine derivatives, especially in concentrated doses, are used pharmacologically in cases of medical emergencies. Situations that cause the body to go into shock, namely a severe allergic response or anaphylaxis or a sustained asthma attack, can result in a very low blood pressure. The caffeine causes a direct increase in stress hormone production, namely epinephrine and also known as adrenaline. The article, "Circulating Catecholamines," by Richard E. Klabunde, Ph.D., notes that the stress hormone attaches to receptors on blood vessels and heart muscle that can cause constriction and increased heart rate, effectually raising blood pressure.

Conclusions

The average American's intake of caffeine from coffee alone is 2 to 4 cups per day, which is equivalent to approximately 200 to 400 mg of caffeine per day. A 2010 "Journal of Women's Health" article concluded that a six-day, 240 to 250 mg dose of caffeine per day trial resulted in an increase of blood pressure in healthy, non-hypertensive, men and women across all age groups. The American Heart Association establishes their safe caffeine range, with relation to blood pressure and heart disease, between 1 and 2 cups or 100 to 200 mg per day.