Researchers at Cornell University recently published a blind study examining how caffeine affects coffee-drinkers sense of taste. The study split 107 participants into two groups. One group received coffee that contained 200 milligrams of caffeine, the other received decaffeinated coffee. Despite the fact that both types of drinks had been sweetened with the same amount of sugar, those who drank decaf claimed their coffee tasted sweeter than those who had drank the coffee with caffiene, IFLScience.com reported. The study was recently published in the Journal of Food Science.
"When you drink caffeinated coffee, it will change how you perceive taste - for however long that effect lasts," senior author Robin Dando said in a statement. In this instance however, the coffee only influenced the perception of sweetness, not on bitter, sour, salty, or umami.
This appears to be linked to caffeine's suppression of the adenosine receptors, which play a role in how relaxed or tired you feel. This also decreases your ability to taste sweet food, and, unfortunately, causes you to crave more of it.
The researchers also found that participants from both groups reported feeling more awake, regardless of whether or not the coffee they consumed contained caffeine or was decaffeinated. Dando compared to to Pavlov's dog. "The act of drinking coffee - with the aroma and taste - is usually followed by alertness. So the panelists felt alert even if the caffeine was not there."