Researchers from the University of Florida examined 10 16-ounce decaffeinated drip-brewed coffees from nine local coffee houses or national chains for caffeine content using gas chromatography. The researchers found that every serving of coffee but one -- instant decaffeinated Folgers Coffee Crystals -- contained caffeine.
While a regular 8-ounce cup of brewed coffee usually contains 85 milligrams of caffeine, the researchers found that the brands of caffeine-containing decaf had caffeine ranging from 8.6 milligrams to 13.9 milligrams.
During the second phase of the study, the researchers analyzed 12 samples of Starbucks decaffeinated espresso and brewed decaf coffee purchased from a single store. The decaf espresso drinks contained 3 to 15.8 milligrams of caffeine per shot, while the brewed decaf coffees contained 12 to 13.4 milligrams of caffeine per 16-ounce serving.
"If someone drank five to 10 cups of decaffeinated coffee, the dose of caffeine could easily reach the level present in a cup or two of caffeinated coffee," said the study's co-author Dr. Bruce Goldberger, director of UF's William R. Maples Center for Forensic Medicine. "This could be a concern for people who are advised to cut their caffeine intake, such as those with kidney disease or anxiety disorders."
Co-author Dr. Mark S. Gold, professor of psychiatry, neuroscience and community health and family medicine at the UF College of Medicine, said that although the concentrations of caffeine in decaf coffee drinks is relatively low, some people could develop a physical dependence on the beverages.
Consumer advocate Mike Adams, author of "Grocery Warning," called decaffeinated coffee beverage claims a "sham."
According to Adams, "Decaffeinated coffees are not decaffeinated beverages; they are actually reduced-caffeine beverages that still contain caffeine. In addition, they may also contain trace amounts of cancer-causing chemical solvents used in the decaffeination process."
"Carefully controlled studies show that caffeine doses as low as about 10 milligrams can produce reliable subjective and behavioral effects in sensitive individuals," said Dr. Roland Griffiths of Johns Hopkins School of Medicine. "The important point is that decaffeinated is not the same as caffeine-free."