Does caffeine dull the perception of sweetness?
DEAR DOCTOR: Does drinking coffee really increase the craving for sweets? I tend to drink a lot of coffee throughout the day, and if it’s true, it explains a lot about my dietary choices.
DEAR READER: While recent studies have found a connection between caffeine and the urge for something sweet to eat, the cause and effect isn’t quite that direct. It’s not the coffee itself that somehow makes us long for the doughnut or Danish, but rather how caffeine affects certain chemical processes within our bodies.
Our daily coffee (or tea or cola or energy drink) habits give us that boost because the caffeine they contain cuts off access to the adenosine receptors in our brain. Adenosine is a chemical that helps to regulate our internal clocks. It gradually builds up throughout the day, and, as it reaches a certain level, we begin to feel sleepy. By blocking those adenosine receptors with caffeine, we get a sense of energy and alertness.
But scientists at Cornell University found that in addition to giving us a jolt, caffeine dulls our ability to perceive sweetness. When the researchers divided the study’s participants into two groups, one that drank decaffeinated coffee and the other that drank regular coffee, the members in the caffeinated group were
unable to accurately gauge the sweetness of a sugar solution. They rated it as markedly less sweet than the decaf group did.
The caffeine drinkers’ palates also remained dulled to the taste of sugar for at least 15 minutes after drinking their high-octane coffee. Because many people continue to reach for caffeinated beverages throughout the day, researchers suspect that the ability to taste sweetness remains suppressed.
This new insight dovetails with the group’s previous research, which found that limiting a person’s ability to taste sweetness actually creates a craving for it.
The study also had some surprising news about how we perceive the effects of caffeine. Although neither group knew whether they were the ones drinking the decaf, almost all the study participants thought that they were the ones who got the caffeine. When they were asked to rate how alert they felt after drinking their particular beverage, both groups reported feeling equally energized.
Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)
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