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Caffeine is a substance that exists naturally in certain plants. It can also be produced synthetically and used as an additive in food products. It is a central nervous system stimulant and a diuretic.

Caffeine is absorbed and distributed very quickly. After absorption, it passes into the brain.

Caffeine does not accumulate in the bloodstream nor is it stored in the body. It is excreted in the urine many hours after it has been consumed.

Caffeine will not reduce the effects of alcohol, although many people still believe a cup of coffee will "sober-up" an intoxicated person.

Caffeine may be used as a treatment for migraine headaches and in relieving, for a short time, fatigue or drowsiness.

Caffeine is widely consumed. It is found naturally in the leaves, seeds, and fruits of more than 60 plants, including tea leaves, kola nuts, coffee, and cocoa beans. It is in coffee, tea, chocolate, cocoa and some colas.

Caffeine is frequently added to over-the-counter medications such as pain relievers, appetite suppressants, and cold medicines. Caffeine has no flavor and can be removed from a food by a chemical process called decaffeination.

Excessive caffeine intake can lead to a fast heart rate, excessive urination, nausea, vomiting, restlessness, anxiety, depression, tremors, and difficulty sleeping.

The effect of caffeine on health has been widely studied. In particular, the effects of caffeine on fibrocystic breast disease, heart and blood vessel disease, birth defects, reproductive function, and behavior in children has been closely examined. The American Medical Association Council on Scientific Affairs says that moderate tea or coffee drinking likely has no negative effective on one's health, as long as the person lives an otherwise healthy lifestyle. However, the organization emphasizes moderate caffeine use.

Abrupt withdrawal of caffeine may cause headaches, drowsiness, irritability, nausea, vomiting, and other symptoms. Reduce caffeine intake gradually to prevent any symptoms of withdrawal.

Three 8 oz. cups of coffee (about 250 milligrams of caffeine) per day is considered an average or moderate amount of caffeine.

Ten 8 oz. cups of coffee per day is considered excessive intake of caffeine.

How much caffeine a child receives should be closely monitored. Although caffeine is safe in moderate amounts, it may negatively affect a child's nutrition. Caffeinated beverages may be replacing nutritious drinks such as milk. A child who consumes caffeine may also eat less, because caffeine suppresses the appetite.

There is no nutritional requirement for caffeine, so it can be completely restricted in a child's diet. Caffeine is a stimulant. Avoiding caffeine may be necessary for a hyperactive child.

If you are pregnant or if you have coronary heart disease or peptic ulcers, your health care provider may recommend that you limit or avoid caffeine intake.

Many drugs will interact with caffeine. Consult with your health care provider or pharmacist about potential interactions with caffeine whenever you take medications.

Diet - caffeine

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.