From many media reports in recent years, coffee drinkers have come to expect sluggishness and headaches as a result of missing their daily cup. Yet, an article in the Journal of Pharmacology (December 1999) challenges these common expectations and suggests that the symptoms from skipping the caffeine in coffee are not as common or as severe as some reports suggest.
The authors, a research team from Harvard Medical School, MDS Harris (a clinical testing facility for drugs and consumer products), and the University of Pennsylvania, began their investigation by adding caffeine-related questions to a demographic and medical survey of 11,112 people who called a testing facility following publicity asking for volunteers for drug and consumer product testing. Of those surveyed, 6,815 people (61%) said they had caffeine from beverages such as coffee, tea, and colas on a daily basis. Only about 1 in 10 of daily caffeine consumers reported symptoms of caffeine withdrawal if they stop consuming caffeine suddenly. Less than 3 percent said their symptoms were severe enough to interfere with daily activities.
Of those reporting symptoms, 57 individuals were recruited for an intervention trial to gather more detail about the stated symptoms. The 14-day intervention trial used popular brands of caffeinated and decaffeinated instant coffees, but the participants did not know which coffee they were receiving during the trial.
Participants were asked to write down the beverages they consumed each day and to comment on the flavor and aroma of the coffee provided. They were also asked to say whether they liked and would purchase the coffee.
Participants also rated their moods and attitudes during the study. For example, they answered questions such as, "How relaxed were you today?"; "How alert were you today?"; and "Did you feel healthy and vigorous today?" Even though the participants were told in advance that caffeine content was one feature of the coffees they were evaluating, they were unaware that caffeine withdrawal was under scrutiny because of the variety of other information requested.
During the trial, the 57 individuals were divided into three groups. One group received caffeinated coffee during the entire trial. A second group received caffeinated coffee for 5 days, then decaffeinated coffee for 7 days and finally caffeinated coffee for 2 days. Thus, for the second group, caffeine was suddenly withdrawn. Even so, the authors state, "Only six of the 18 subjects reported symptoms on the first two days of no caffeine." Women reported more changes in mood and attitude than the men did. The researchers suggest that future studies address how men and women may differ in their perception of caffeine withdrawal.
In the third group, participants drank caffeinated coffee for 5 days, followed by coffee blends that contained less and less caffeine each day over the next 7 days. By the end of the trial these participants were drinking coffee without caffeine. Although some participants in this group did report symptoms of caffeine withdrawal, there was no consistent pattern to their symptoms.
Other feelings noted by some participants included feelings of being tired or jittery, gastrointestinal problems, and headaches; however, there were no consistent symptom patterns. For example, feeling tired did not necessarily match consumption of a lower level of caffeine. Even participants in the first group reported symptoms, even though they had the same amount of caffeine in their coffee throughout the trial.
The researchers point to three important and unique features of their study in comparison with previous studies of caffeine withdrawal:
- Their study included more participants than other similar studies.
- The participants did not know the topic of the research.
- A segment of the participants was evaluated during a period of gradual caffeine withdrawal.
These features helped to minimize problems with bias in the study design.
Consumers regularly choose to consume caffeine-containing foods and beverages. Many report feeling uncomfortable or complain of headaches, nausea, fatigue, and muscle aches when they suddenly stop consuming these foods or beverages. Yet, these symptoms have not been documented in a scientific way.
The researchers point out that it appears that many more people report a history of withdrawal symptoms than show them when evaluated under blind conditions. According to researcher Dr. Charles O'Brien, "The dramatic thing about this study is the unexpected anecdotes from the subjects such as the person who reported withdrawal symptoms but who, as part of the study, had not had a change in consumption." Dr. Peter Dews adds, "I am impressed by the frequency that symptoms associated with caffeine withdrawal are reported when there is no reason to suppose there has been a change in caffeine consumption. On average, 18 percent of subjects in all groups on all days reported symptoms. When caffeine was abruptly withdrawn, 27 percent of subjects reported symptoms shortly thereafter. On the same days, 44 percent of the subjects in the group whose caffeine was not changed reported symptoms!"
The researchers further note, "Perhaps a more important observation for evaluating the public health implications of caffeine withdrawal is that even among the people who say they have symptoms, few report these symptoms to be incapacitating."
This study was supported by the North American Branch of the International Life Sciences Institute. Doctors Peter B. Dews, Charles P. O'Brien, Gary L Curtis and Kathryn J. Hanford were responsible for the conduct of the study.
For more information on caffeine and health, the IFIC Review Caffeine: Clarifying the Controversies is available online at http://ific.org/publications/reviews/caffeineir.cfm.
