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Study: Caffeine May Add Zing to Cola, But It Doesn't Add Flavor


Griffiths tells WebMD, "Caffeine is the most widely consumed psychoactive -- mood altering -- drug in the world. At doses that are delivered in a can of soft drink, it produces mood and behavioral effects. Those mood effects are well known to most consumers of caffeine, and they include things like increased sense of well-being, increased alertness, concentration, some increased sociability, and decreased sleepiness."

The downside, however, is that daily consumption of caffeine in doses equivalent to two to three cans of soft drinks a day produces physical dependence, indicated by withdrawal symptoms when caffeine users try to go cold turkey, Griffiths adds. Characteristic symptoms of caffeine withdrawal include headache, tiredness, lethargy, and sometimes irritability; in extreme cases, people can have flu-like symptoms, nausea, and vomiting.

"We also know that the development of physical dependence is intimately linked to the continued daily administration of compounds that contain caffeine, so that most people who are regular consumers of caffeine are waking up in the morning and taking caffeine, experiencing the elevation in mood, and not recognizing that by not having caffeine overnight, they're actually in a low-grade withdrawal state. Caffeine is suppressing low-grade withdrawal symptoms, and it's that mechanism that is so important to the [regular use of the product]," Griffiths says.

In their study, Griffiths and Vernotica recruited volunteers who reported drinking cola at least once a week, and who expressed a preference for a specific brand of cola based on flavor and caffeine content. The prospective tasters were secretly screened for their ability to distinguish between regular and diet Coke; subjects who couldn't tell the difference (seven of 32) were then excluded.

The researchers then put the remaining 25 participants through six tasting sessions in which the concentration of caffeine in the drinks was increased. All sessions used cola from the same batch, and each consisted of 25 trials in which tasters compared two samples of cola solution labeled "A" and "B."

For the first five trials of each session, the tasters were put through their paces in a "warm-up," in which they were informed about whether they were tasting sample A or B as a means of heightening awareness of flavor differences (they were not, however, told which contained caffeine). The study subjects then downed each of two samples, with each tasting separated by a rinse with bottled spring water.

At the lowest caffeine concentration, none of the tasters could tell the difference between the two samples. At a level of caffeine similar to or slightly higher than that found in either Coke classic or Pepsi, only two of the 25 were able to discriminate between the caffeinated and decaffeinated versions. It wasn't until tasting colas with caffeine concentrations far above those allowed by the FDA that the remainder of the subjects began noticing a difference.

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