Caffeine-containing beverages, foods and even medications are so much a part of 21st century life that it's easy to overlook the fact that caffeine is a drug. First isolated from coffee in the early 19th century, caffeine is a psychoactive stimulant. While you may depend on your morning coffee to get you revved up for the day ahead, others are more sensitive to the substance and may have mild to severe reactions from ingesting it.
Caffeine Intolerance
Most healthy adults can tolerate moderate amounts of caffeine -- 200 to 300 mg, or the equivalent of 2 to 4 cups of coffee daily -- with no ill effects, according to MayoClinic.com. However, even among those with no particular sensitivity to caffeine, overindulgence can produce a number of unpleasant symptoms, including insomnia, irritability, muscle tremors, nervousness, rapid heartbeat and stomach upset. What sets the caffeine intolerant apart from most people is their inability to ingest even small amounts of the substance without triggering unwelcome symptoms.
Mild Symptoms
Caffeine intolerance's mild symptoms are similar to those experienced by caffeine-tolerant individuals who consume more caffeine than their systems can readily process. However, it takes no more than a cup of coffee or tea to set off such symptoms in those who are intolerant of caffeine. Anxiety, restlessness and insomnia are among the milder symptoms of caffeine intolerance. MayoClinic.com points out that research indicates that men are generally more sensitive to caffeine than women.
Allergy-Like Symptoms
There is a thin line between intolerance and allergy, and some people sensitive to caffeine experience more extreme reactions to the substance. In these cases, depending on the degree of allergic reaction, symptoms range from moderate to severe. The symptoms of all food allergies are fairly similar, according to the University of Maryland Medical Center, and range from itching and rashes to difficulty swallowing or breathing. Other symptoms include nausea, vomiting, diarrhea, lightheadedness, dizziness, a metallic taste in the mouth, wheezing, nasal congestion, swelling of the throat and rapid pulse.
Caffeine Content
Although you probably are aware that coffee, tea, cola drinks, and some over-the-counter drugs contain caffeine, you may not realize the degree to which caffeine levels vary between various products. For example, an 8-oz. cup of brewed coffee averages 133 mg of caffeine but can range from a low of 102 to a high of 200 mg, according to the Center for Science in the Public Interest. Brewed tea ranges from 40 to 120 mg per 8-oz cup, and 12-oz. cola drinks range from a low of 35 mg to a high of 72 mg. The caffeine levels in energy drinks range from 48 to 300 mg, depending on the brand and size of serving. Caffeine is also found in some over-the-counter medications, including analgesics and drugs marketed to help keep consumers awake and alert. Chocolate and desserts containing chocolate and/or coffee also contain caffeine, but levels are generally minimal.
References
- "The Facts About Caffeine"; Lorrie Klosterman; 2006
- MayoClinic.com; Nutrition & Healthy Eating: Caffeine: How Much Is Too Much?; March 2011
- University of Maryland Medical Center; Complementary Medicine: Food Allergy; David Ziev, et al.; Dec. 2009
- Center for Science in the Public Interest: Caffeine Content of Food & Drugs; September 2007Drugs
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