Caffeine and Its Effects

Caffeine is the most important chemical in coffee. It is an odorless and slightly bitter solid. Caffeine mostly affects the brain, kidneys, and the cardiovascular (heart and blood vessels) system, but it also increases metabolism and breathing. A five ounce serving of regular coffee contains about 90-125 milligrams of caffeine; whereas, an equal amount of tea only contains 30-70 milligrams of caffeine. A soft drink only has about 37 milligrams of caffeine per five ounces.

Coffee has several effects on the human body:

• it helps to increase circulation of the blood
• it can cause nervousness and loss of sleep when taken in large amounts
• it can speed up a person's thoughts
• it produces a feeling of well-being
• it gives some people the ability to memorize simple numbers, concepts, and thought sequences easier
  

If you drink one or two cups several times a day, coffee will have little effect on the cardiovascular system. However, if you drink three to four cups several times a day, it will slow your pulse rate, raise blood pressure, contract blood vessels that are right under the skin, and dilate blood vessels of the kidneys, muscles, skin, and heart. Finally, caffeine makes the heart contract harder while it's pumping.