Twenty-five regular soda drinkers were tested to make sure that they were able to distinguish between Diet Coke and Coke, a sign that they had reasonable taste sensitivity. Then, during testing sessions, each subject sipped from 50 cups of Coke, one pair at a time, to see if they could distinguish between caffeine-free Coke and regular Coke. Scientists found that only two of the study's subjects could detect caffeine in a cola that has a caffeine concentration of .1 milligram per milliliter, which is the concentration found in soft drinks like Coca-Cola Classic and Pepsi . Griffiths said that the results of this study suggest that the addictive and mood altering effects of caffeine play a bigger role than taste in the large consumption of cola. About 70 percent of all soft drinks in the United States contain caffeine.
Withdrawal symptoms can include headaches and lethargy that last up to two days.
Caffeine has been added to cola for years. Until 1920, cola manufacturers boasted in their advertising about caffeine's value as a stimulant. This type of advertising stopped when the U.S. government questioned the use of caffeine in colas. In 1981, the Food and Drug Administration again reviewed the effects of caffeine in soft drinks, at which time cola manufacturers argued that caffeine was vital for the drinks' flavor. Inc. All rights reserved.