Caffeine in colas: 'The Real Thing' isn't the taste

August 14, 2000

"The marketing parallels between nicotine and caffeine are pretty stunning"

The majority of people who drink colas can't tell whether a soda contains caffeine or not, according to a new Johns Hopkins study. "This stands in sharp contrast to the claim some soft drink manufacturers make that they add caffeine purely for taste," says psychopharmacologist Roland Griffiths, Ph.D., who directed the research.

In a study of 25 adult cola drinkers, the scientists found that only 8 percent of them could detect caffeine in cola at a concentration of 0.1 milligram per milliliter, the concentration in Coca-Cola Classic or Pepsi. The rest of the group couldn't taste the difference between caffeine-containing and caffeine-free cola until caffeine levels were raised to much higher levels beyond those approved by the U.S. Food and Drug Administration (FDA).

The report appears in this month's Archives of Family Medicine.

"I'd like to see the soft drink industry come out of denial about the role of caffeine in their products," says Griffiths. "They're adding a mildly addictive, mood-altering drug, one which surely accounts for the fact that people drink far more sodas with caffeine than without." About 70 percent of all soft drinks in this country contain caffeine, he adds. The caffeine-free versions of Coca-Cola Classic and Pepsi, the two most popular soft drinks, make up only 5 percent of sales of those sodas.

"Given that sodas are aggressively marketed to kids, manufacturers should openly say why the caffeine is there. We should tell what the caffeine dose is. It's a case of knowing what you're getting and why.

"The marketing parallels between nicotine and caffeine are pretty stunning," says Griffiths. "Both are psychoactive drugs. Until recently, cigarette companies denied that nicotine is addicting and said it was added merely as a flavor enhancer for cigarettes. The same is being said for caffeine." In 1998, Americans guzzled 15 billion gallons of sodas, the equivalent of 585 cans for every man, woman and child. Consumption of soft drinks has more than doubled since 1975 and more sodas are consumed than water, says Griffiths. Soft drinks also represent the single largest source of added sugar in the U.S. diet, according to sources cited in the study, and increased soda drinking in children displaces eating more nutritious foods, possibly increasing tooth decay, obesity and bone fracture.

"We know adults and children can become physiologically and psychologically dependent on caffeinated soft drinks, experiencing a withdrawal syndrome if they stop," says Griffiths. Earlier research at Hopkins shows that withdrawal symptoms typically include headache and lethargy, and last a day or two.

"Most adults can become informed about, and cope with, withdrawal," says Griffiths.

"But it is more problematic in children who are less well-informed and whose soft drink consumption may be sporadic. Then children may go in and out of withdrawal and have erratic periods of suboptimal feelings that could affect the way they function."

In the study, the scientists first made sure that subjects could distinguish Diet Coke from regular Coca-Cola a sign that they had reasonable taste sensitivity. Then, during the actual test sessions, subjects sipped from 50 cups of soda, a pair at a time, to see if they could distinguish between caffeine-free Coke and that with added caffeine. Subjects were paid $10 per session and 25 cents for each correct answer. The first five trials in each session were "warm-up" trials, in which participants were told what they were drinking.

"We tried hard to design this study so it would be a fair test of whether caffeine affects cola taste," says Griffiths. The scientists used cola from a single production batch for each study session; subjects were required to rinse their mouths with water after tasting each sample. The "warm up" trials were added to heighten the ability to taste a difference. Subjects were chosen in part because they were regular cola drinkers who believed they preferred caffeinated colas because of their taste. That fact and the money reward helped ensure that they were motivated to participate, says Griffiths.

Caffeine has long been added to colas, he adds. Early advertisements played up its value as a stimulant until about 1920, when the U.S. government questioned its use in soft drinks. "The objections, however, were countered by industry," says Griffiths, "and sodas continued to contain caffeine. In 1981, the FDA again reviewed addition of caffeine to soft drinks to see if they should maintain their GRAS (generally recognized as safe) status.

"Nobody knew much then about caffeine's behavioral or mood-altering effects at low doses. Industry scientists again countered queries, this time with studies that appeared to show how important caffeine was to flavor.

"Since then, though, the picture has changed," says Griffiths. "Soft drink consumption has gone through the roof. There's marketing of larger volumes of soda drinks like the Big Gulp, and industry has now started targeting advertising to children."
Johns Hopkins Medical Institutions' news releases are available on an EMBARGOED basis on EurekAlert at, Newswise at and from the Office of Communications and Public Affairs' direct e-mail news release service. To enroll, call 410-955-4288 or send e-mail to

On a POST-EMBARGOED basis find them at, Quadnet at and ScienceDaily at

Ellen M. Vernotica, Ph.D., was a co-researcher in this study, which was funded by the National Institute on Drug Abuse.

Related Web Sites: for a soft drink site from the Center for Science in the Public Interest

Media Contacts:
Karen Infeld 410-955-1534 (August 9-11)

Marjorie Centofanti 410-955-8725 (contact as of August 14)

Johns Hopkins Medicine

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