Coffee, created by infusing ground coffee beans with water, is one of the most popular beverages in the world. One component of coffee that may have major effects on health is caffeine, an alkaloid stimulant naturally present in coffee beans. Even decaffeinated coffee contains a small amount of caffeine, although it is generally not enough to have significant health effects.
Amounts
Brewed coffee contains between 95 and 200mg of caffeine per 8 oz. cup. The same size cup of decaffeinated coffee contains between 2 and 12mg of caffeine. An 8 oz. cup of instant coffee has 27 to 173mg of caffeine, and instant decaffeinated coffee contains 2 to 12mg per cup. One ounce of espresso from a coffee shop has about 58 to 75mg of caffeine. Moderate consumption of caffeine is considered to be about 300 to 400mg a day, equivalent to about two to three cups of coffee.
Mental Effects
Caffeine has a strong effect on mood and mental state. After a cup of coffee, most people feel more alert and experience an elevation in mood. Caffeine in coffee reduces fatigue and can temporarily improve work performance. According to the Linus Pauling Institute, moderate consumption of coffee with caffeine may reduce the risk of suicide in individuals with suicidal thoughts.
Blood Pressure
The caffeine in coffee may cause a sudden increase in blood pressure in some people, according to MayoClinic.com. For affected individuals, the systolic pressure, the top number of a blood pressure reading that indicates the pressure during a heart contraction, rises between 3 and 14 points. The diastolic pressure, the lower number on the reading that indicates the pressure when the heart is at rest, rises between 4 and 13 points. This effect is short-term and dissipates quickly, so no long-term effect on blood pressure is noted.
Special Circumstances
During pregnancy, caffeine is transmitted across the placenta into the baby's body. While it is still under study, preliminary research suggests that caffeine consumption over 200mg a day may increase the risk of miscarriage. Nursing mothers can also pass caffeine to their baby through breast milk. Babies who receive excessive caffeine this way may be more irritable or have more trouble sleeping than other babies their age.
Overdose
Excessive caffeine intake can cause a myriad of symptoms, which tend to be mild and temporary. Individuals who have consumed 10 8-oz. cups of coffee or more in a single day are likely to experience a rapid heart beat, nausea, vomiting, restlessness, anxiety, excessive urination, depression, muscle tremors and insomnia. These symptoms resolve after the caffeine has cleared the system, typically within a few hours to a day after consumption.
Withdrawal
Caffeine in coffee is considered a mildly addictive substance. People who are used to drinking large amounts of coffee every day frequently experience withdrawal headaches that begin 12 to 24 hours after the last cup of coffee. Other withdrawal symptoms include irritability, anxiety, drowsiness, nausea and vomiting. Symptoms typically clear up after 24 to 48 hours without caffeine.
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