At the end of a day, you might order a cup of decaf coffee to avoid the anxiety and sleeplessness that can come with a full-strength caffeine kick of regular joe. Nice try. Despite its name, decaf isn't quite caffeine-free.
The process of decaffeination, it turns out, cannot remove caffeine completely. In fact, if you drink five to 10 cups of decaffeinated coffee, you could get as much caffeine as from drinking one or two cups of caffeinated coffee, according to researchers who tested the caffeine levels in several decaf coffee.
In 2007, Consumer Reports measured how much caffeine was in small-sized (10 or 12 ounces) cups of decaf coffee from Burger King, Dunkin' Donuts, McDonald's, Seattle's Best Coffee, 7-Eleven, and Starbucks. They found that although more than half of the coffees had less than five milligrams of caffeine, samples from Dunkin' Donuts had 32 mg, Seattle's Best had 29 mg and Starbucks had 21 mg.
By comparison, a regular cup of coffee has approximately 85 mg of caffeine. So while the trace amounts of caffeine in decaf may not be enough to kill you , they could be enough to blame for your jitters.
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