Coffee is a complex mixture of chemical components of the coffee bean. Some of these components are partially destroyed by the roasting process; however, many of these components are not. Caffeine is one of the components that is not affected by the roasting process. With the addition of hot water, the caffeine is extracted from the coffee bean.

Caffeine was discovered in coffee in 1820. Caffeine is an alkaloid that acts as a mild stimulant. It increases the blood pressure, stimulates the central nervous system and the action of the heart and lungs, and promotes urine formation. It also acts as a diuretic and delays fatigue. Caffeine does have some positive side effects. It has been found to help treat migraines since it helps constrict the dilated blood vessels, therefore reducing the pain. It also has been documented to increase the potency of aspirin and to slightly relieve the affects of asthma attacks. It has been suggested that caffeine has been linked to possible cancers and birth defects. However, this has not been confirmed and there are no bans or warnings that have been issued by the US Food and Drug Administration (US FDA).

The amount of caffeine found in the coffee beans varies. On average, a regular cup of coffee contains approximately 90 to 150 mg of caffeine. Coffee brewed in a drip coffee maker has about 115 to 175 mg of caffeine while other coffee makers may brew coffee with about 80 to 135 mg. Typically, espresso has about as much caffeine as a regular cup of coffee. On average, a standard espresso cup would have about 100 mg of caffeine. However, the serving size for espresso is much smaller. The actual content of caffeine per milliliter in an espresso is much higher than in a regular brew. Also, caffeine is assimilated quicker when ingested in a concentrated dosage such as an espresso cup.

The amount of caffeine found in coffee blends will also vary. The following are examples of the caffeine content for different coffee blends:

-Brazilian Bourbons: contains 1.20% caffeine
-Columbia Excelso: contains 1.34% caffeine
-Columbia Supremo: contains 1.34% caffeine
-French Roast: contains 1.22% caffeine
-Costa Rican Tarrazu: contains 1.35% caffeine
-Vienna Roast: contains 1.27% caffeine
-Decafs: contains 0.02% caffeine

People hypersensitive to the caffeine found in coffee may decide to drink decaffeinated coffee. This way, they can still enjoy the great coffee taste, yet avoid the caffeine. Coffee can be "decaffeinated" by treating the green beans with solvents called chlorinated hydrocarbons. Once the solvents are removed, the beans are then roasted by ordinary procedures. Most people become accustomed to decaffeinated coffee and do not have to worry about the effects of caffeine.