Coffee drinkers beware - decaffeinated is not the same as caffeine-free, according to a new study.
In fact, researchers in Florida have discovered that almost all decaffeinated coffee contains some caffeine. They say people who switch to decaf for health reasons, such as high blood pressure, may be getting more than they bargained for.
"If someone drinks 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. This could be a concern for people who are advised to cut their caffeine intake, such as those with kidney disease or anxiety disorders", said study co-author, Dr Bruce Goldberger of the University of Florida.
He pointed out that despite caffeine's widespread use, most medical textbooks contain no guidelines for intake, even though low doses might adversely affect some people.
The study involved two phases. In the first phase, researchers purchased 10 decaffeinated coffee beverages from nine national chains or local coffee stores. All of the drinks were 16oz and every serving except one contained caffeine, ranging from 8.6 milligrams to 13.9. An 8oz cup of coffee typically contains 85 milligrams of caffeine.
In the second phase of the study, the researchers analysed 12 samples of Starbucks decaffeinated espresso and brewed decaffeinated coffee taken from a single store. The espresso drinks contained between three and 15.8 milligrams of caffeine per shot, while the brewed coffee had caffeine concentrations ranging from 12 to 13.4 milligrams per 16oz serving.
While the amount of caffeine found in the beverages was low, some people could conceivably develop a physical dependence on them, insisted study co-author, Dr Mark S. Gold.
"One has to wonder if decaf coffee has enough, just enough, caffeine to stimulate its own taking. Certainly, large cups and frequent cups of decaf would be expected to promote dependence and should be contraindicated in those whose doctors suggested caffeine-free diets", Dr Gold said.
Even moderate caffeine levels can increase agitation, anxiety, heart rate and blood pressure in some susceptible individuals, the researchers added.
Details of these findings are published in the Journal of Analytical Toxicology.