The Use of Caffeine

What is caffeine?


Caffeine is a commonly consumed drug. It is found in various beverages such as tea, coffee, cola-flavored carbonated beverages and in chocolate products. Caffeine is also added to a variety of other carbonated beveragesand is an ingredient in a number of non-prescription drugs such as headache, cold, allergy, pain relief, and stay awake pills.

About 80 percent of the adult population in the US consume caffeine, and about 20 percent consume over 350 mg daily – a level sufficient to cause physical dependency.

What affects the caffeine content of a product?

The method of preparation of tea and coffee determines the caffeine content of the beverage. An average cup of instant coffee contains about 65 mg while percolated coffee contains about 110 mg/cup. Tea and most caffeinated soft drinks contain about 30-65 mg/serving. Hot chocolate beverages contain about 5 mg caffeine/cup while chocolate candy may contain between 10 and 40 mg per 2 oz bar.

Is caffeine harmful?

Physiological effects of caffeine can be seen in adults at doses of only 100-200 mg. This is readily achieved with 1-3 cups of coffee. On a body weight basis children, aged 1-5 years, are the heaviest consumers of caffeine. A child consuming one can of caffeinated soda receives a caffeine equivalent of 4 cups of coffee for an adult.

Caffeine is readily absorbed by the body, with blood levels peaking about 30 minutes after ingestion. The clearance rate from the blood varies from several hours in an adult to several days in a newborn. The clearance rate is decreased by pregnancy and use of oral contraceptives. Smoking, on the other hand, appears to increase the rate at which caffeine is cleared from the body. Hence, caffeine intake should be greatly reduced or eliminated by persons trying to quit smoking, so as to prevent increased caffeine levels in the blood and the possible increased craving for nicotine.

Caffeine can produce many effects including:

  • elevated blood sugar (gives the feeling of an energy surge)
  • elevated blood fats
  • increased blood pressure
  • stimulated central nervous system (may cause one to override the body’s call for rest)
  • irregular heart beat
  • increased urinary calcium and magnesium losses (may impact on long-term bone health)
  • increased stomach acid secretion (aggravates a stomach ulcer)
  • tremors, irritability, and nervousness
  • insomnia and disruption of sleep patterns
  • anxiety and depression
  • heightened symptoms of premenstrual syndrome (PMS)

How does caffeine affect the fetus?

Since caffeine crosses the placenta and is metabolized by the fetus very slowly, the fetus may be at risk of exposure to significant amounts of caffeine from its mother. In animal studies, high doses of caffeine cause skeletal birth defects, retarded fetal growth, reduced birth weight, and increased stillbirths while lower doses equivalent to only two cups coffee/day may cause slowed bone growth. Subtle neurobehavioral effects persisting into adulthood have been reported in rats exposed to modest doses of caffeine. Caffeine consumed by males prior to mating can also produce significant fetal growth retardation.

Some population studies have shown that high levels of caffeine intake by pregnant women are associated with a higher than normal incidence of prematurity, lower birth weights, and reduced head circumference. Based on available data, the FDA has advised pregnant women to avoid all caffeine during pregnancy.

Does caffeine contribute to disease?

The risk of several diseases have been shown to be affected by caffeine consumption including cardiovascular disease and cancer.

Cardiovascular Disease

Caffeine abstainers, given a dose of 1-3 cups of coffee, show a substantial increase in their blood pressure, while chronic users show much less of an effect. Most physicians recommend the reduction or cessation of caffeine use in cases of heart palpitations or irregular heart beat, since caffeine may initiate cardiac arrhythmia. Furthermore, a number of studies have found that coffee intake is associated with elevated levels of blood cholesterol and blood triglycerides. A recent study found that even the use of decaffeinated coffee (more than 4 cups/day) increased the risk of heart disease. The Adventist Health Study found that the use of coffee was associated with a 50 percent increase in the risk of heart disease in men and 10-20 percent increased risk for women.


While animal studies reveal that caffeine alone does not cause cancer, caffeine or coffee appears to enhance the frequency with which other carcinogens induce tumors. There are several studies which have linked the use of coffee with human cancers. Adventists who use coffee are reported to have a greater risk of colon and bladder cancer. Coffee consumption has been implicated in cancer of the kidney, ovaries, and large bowel, while tea consumption has been associated with an increased risk of cancer of the rectum, but not the colon.

Caffeine and other methylxanthines (theophylline in tea and theobromine in chocolate) have been suggested as possible risk factors for breast cancer. Methylxanthines have been reported to increase the severity of fibrocystic breast disease, a benign breast disease, which may increase the risk of breast cancer. Methylxanthines have been reported to increase the severity of fibrocystic breast disease, a benign breast disease, which may increase the risk of breast cancer. Some researchers suggest that if methylxanthines are removed from the diet symptoms will improve.

Gastrointestinal Effects

Coffee and tea significantly reduce iron absorption by 40 percent and 60 percent respectively. Caffeine itself has a negative effect on calcium balance by reducing both calcium absorption and increasing the calcium lost through the urine. Coffee also decreases lower esophageal sphincter pressure, possibly contributing to heartburn.

What is caffeinism?

In animals, very high doses of caffeine lead to aggressiveness and psychotic behavior. In humans, levels of 650-1000 mg/day results in the caffeinism syndrome, a condition indistinguishable from anxiety neurosis. Caffeine-sensitive subjects report anxiety and severe depression after a dose of only 300 mg of caffeine. Pediatricians are concerned that many children consuming high levels of caffeine display hyperactive behavior.

Is caffeine addictive?

Many regular users are surprised by the difficulty they experience when they try to quit using caffeine. Dependence, as evidenced by withdrawal symptoms, may occur after only 6-15 days of exposure to 600 mg or more daily.

Individuals who have become addicted to caffeine should expect withdrawal symptoms to begin 12-24 hours after cessation of caffeine intake. These vary in severity with individuals but usually include headache, fatigue, apathy, and possibly anxiety. Withdrawal symptoms usually peak at 36 hours and will be gone at the end of 1 week. Detoxification methods may vary from abrupt abstinence to dose tapering with the use of analgesics to relieve symptoms. Caffeine is an addictive drug and its regular use can lead to dependency with unknown long-term effects. Using a chemical to “feel good” is a behavior which may serve as a gateway to use of other drugs. Since coffee and tea contain numerous compounds other than caffeine which may cause physiological or psychological effects, avoidance of even the decaffeinated beverages is recommended.

What guidelines are recommended?

  1. Choose cereal coffees and herb teas rather than caffeinated coffee, teas, and other caffeine-containing beverages.
  2. Caffeine products should be used only if medically prescribed.
  3. Pregnant and lactating women and young children should avoid all caffeine-containing products.
  4. If chocolate and cocoa products are used, they should be used sparingly or used as flavorings. Carob is a useful alternative for chocolate.
  5. Choose pure water, fruit and vegetable juices as the preferred beverages. If a hot beverage is desired, learn to use safe herbal teas or cereal-based drinks instead of decaffeinated tea or coffee.

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