Caffeine-just what exactly is it?
Medically, caffeine is known as trimethylxanthine. When isolated, it is a bitter white crystalline powder although it also appears naturally in some plants and their leaves.
Caffeine is highly addictive. It operates using similar mechanism that amphetamines, cocaine and heroin use to stimulate the brain. The effects are milder though. Sadly, it has been added to a number of beverages to induce this addictive effect on users to increase sales. This accounts for the numerous products that caffeine is found in on the market from cokes and other sodas to certain foods.
Caffeine is also a central nervous system stimulant and a mild diuretic. Many people who work the night shift has been known to drink potfuls to increase wakefulness. College students cramming for exams also imbibe large amount of coffee containing caffeine to stay awake.
Caffeine and blood pressure
Caffeine definitely raises blood pressure in hypertensive patient as well as those who are not hypertensive - myself included. (Try checking blood pressure about thirty minutes after drinking coffee). According to Sheldon G. Sheps, MD, in the article "Caffeine, how does it affect blood pressure" www.mayoclinic.com, the amount of caffeine in 2-3 cups can raise systolic blood pressure (the top number) 3-14 (mmHg) and diastolic (the bottom number) 4-13 (mm Hg).
How it does this though, is unclear. It is speculated that it stimulates the adrenals to release adrenalin, which raises blood pressure. It has also been suggested that caffeine blocks a hormone that keeps the arteries widened.
Coffee and the GI tract
Caffeine can produce a laxative like effect in susceptible people. It is especially known to induce excess acid production in the stomach, placing it on the dietary black list for ulcer sufferers.
Caffeine can also damage the lining of the intestinese in excessive amounts causing the formation of ulcers and gastritis.
How much is too much?
Again, according to Dr. Shep in the above article, 200-300 milligrams is tops. This represents about four cups per day with about 90-100mg of caffeine per cup.
Above this amount, you are asking for trouble. for safety sake, try to limit caffeine to less than 300mg of two cups per day.