CAFFEINE

On this page

• What is caffeine?
• Caffeine's effect on the body:
  • Positive (or no known negative) effects
  • Minor side effects
  • More serious side Effects
• Should I avoid caffeine during pregnancy?
• Is caffeine addictive?
• What side effects can I expect if I quit?
• What about decaffeinated beverages?
• Caffeine contents
• Further information

What is caffeine? Caffeine is a plant product that is most commonly found in coffee beans, tea, soft drinks, cocoa and chocolate. Caffeine is also found in some prescription and non-prescription drugs, including cold, allergy and pain relievers.

How does caffeine affect the body?  Caffeine acts as a stimulant by exerting a strong effect on the central nervous system. The effects of caffeine on the body may begin as early as 15 minutes and last up to six hours.

Caffeine may increase heart rate, body temperature, blood flow to the skin & extremities, blood pressure, blood sugar levels, stomach acid secretion and production of urine (diuretic).

Positive (or no known negative) effects: When caffeine is consumed in moderate doses (about two 6-oz cups of coffee or about four 12-oz colas), there are no known negative effects. It can decrease drowsiness and increase motor activity. Contrary to popular belief, drinking coffee will not help someone who is intoxicated become sober.

Most individuals consuming moderate amounts (about two 6-oz cups of coffee per day) will experience few, if any, negative side effects. In general, moderate consumption of caffeine does not seem to increase one's risk for irregular heartbeats, heart disease, high cholesterol levels, cancer (including breast cancer), fibrocystic breast disease or infertility.

Minor side effects: Sensitivity to caffeine varies. Some people can drink several cups of coffee or other caffeinated beverages with few side effects. Other individuals may be so sensitive that even a small amount of caffeine makes them uncomfortable.

If people are especially sensitive to caffeine or if they consume more than 250 mg at one time (more than two 6-oz cups of coffee or five 12-oz colas), they may notice minor side effects including insomnia, restlessness, irritability, nervousness, headaches, hand tremors, extra heartbeats and an inability to concentrate.

Less noticeable side effects include a temporary increase in blood pressure, breathing rate and metabolism. Some symptoms of PMS (breast tenderness, irritability and headache) may be increased with caffeine use. Also, some researchers think that caffeine increases the amount of calcium lost in urine and feces. However, as long as people get the recommended amount of calcium each day (1000 mg), the effects of caffeine on the bones seem to be minimal. For more information on calcium in the diet and osteoporosis, see Medline Plus.

More serious side effects: While consuming moderate amounts of caffeine does not seem to have long-term detrimental effects, consuming larger amounts of caffeine on a regular basis (1000 mg or about ten 6-oz cups of coffee a day) may be linked to conception problems, increased episodes of heartburn, and changes in bowel habits.

Too much caffeine may lead to sleep deprivation and a tendency to disregard the normal warning signals that the body is tired and needs rest. Caffeine does not replenish energy or prevent emotional fatigue; food and sleep are the only remedies for these. When normal sleeping patterns are continually disrupted, mood depression may occur. Too much caffeine may also lead to anxiety-related feelings such as excessive nervousness, sweating and tremors.

People who are taking medications for depression, anxiety or insomnia, high blood pressure, other heart problems, chronic stomach upset or kidney disease should avoid caffeine until discussing the matter with a clinician.

If you want to avoid some of the annoying side effects of caffeinated beverages (e.g., jitters or sleeplessness), switching to decaffeinated drinks may help.

Should I avoid caffeine during pregnancy?  Some studies show an association of high doses of caffeine with an increased rate of miscarriages, premature deliveries or low birth weights. However, complicating factors such as smoking and alcohol use were not accounted for. In high doses, caffeine can affect fetal breathing and heart rate. If you are pregnant, or planning to become pregnant, you may want to consider your options such as eliminating caffeine from your diet or limiting intake to no more than 200-300 mg (2-3 cups of coffee) per day. This matter should be discussed further with your clinician.

Is caffeine addictive?  Many people who drink caffeinated beverages become dependent on caffeine. They crave it in order to feel its effects. Many feel they need a caffeinated beverage to get going in the morning.

Some people who drink caffeinated beverages feel that they develop a tolerance to caffeine, needing more and more caffeine to produce the same stimulant effects. It is thought that tolerance occurs because people who drink a lot of caffeinated beverages can metabolize the caffeine faster and therefore want more sooner.

What side effects can I expect if I quit?  People who stop drinking caffeinated drinks may notice several side effects--especially if they are used to consuming large amounts of caffeine. Some symptoms of caffeine withdrawal include headaches, constipation, irritability, nervousness, nausea and muscular tension. These symptoms usually appear about 12-24 hours after someone has stopped consuming caffeine and usually last about one week. It is recommended that you gradually decrease your caffeine intake to avoid withdrawal symptoms.

What about decaffeinated beverages?  The health side effects of decaffeinated beverages are just as widely debated as the effects of beverages containing caffeine. Moderate amounts are unlikely to cause any negative health effects. However, there are other compounds in some decaffeinated teas and coffee that could further irritate existing ulcers and frequency of heartburn.

Caffeine contents:

*Caffeine content of coffee varies depending on type of bean, quantity used, how finely beans are ground and brewing time.
**Not all non-prescription drugs are included. Read labels carefully!

Further information:

University Health Service offers nutrition consultation. See Nutrition Clinic or call 734-763-3760.

See also the Medline Plus article on caffeine in the diet.