Coffee seems to be the most overstudied beverage; seemingly every day we're bombarded with another study about it causing or curing cancer. But surprisingly, there are plenty of scientists who don't really understand its many effects. In fact, it may even be changing the way we taste all the other things we eat in a day, a new study suggests.
Image: Fredrik Rubensson/Flickr
Despite coffee being one of the most widely-consumed drugs, there hasn't actually been much research into its effects on taste. One team of researchers at Cornell had previously noticed that adenosine, a chemical that caffeine blocks when it bestows its wakening effects, seemed to have a corresponding receptor in the taste buds of mice. They tested caffeine's effects in humans, and noticed that it influenced how the subjects perceived sweetness, not just in the coffee, but in other foods as well.
"People think they were born with a sweet tooth or don't like a certain thing," study author Robin Dando from Cornell told Gizmodo. "Maybe taste is much more plastic than that."
And, even stranger, their study calls into question just how much of an effect caffeine has over a placebo.
The researchers tested 107 panelists at Cornell. Around half of the panelists drank sweetened decaffeinated coffee with the caffeine put back in (to control for the amount of caffeine) on the first day. The other half drank sweetened decaffeinated coffee with quinine to replace the bitter flavour of the caffeine, and then tasted various compounds representing sweet, salty, sour, bitter and umami. Neither group knew which they were getting, and received the opposite cup for the next session, according to the study published in the Journal of Food Science.
It turned out the caffeinated coffee tasted less sweet than the quininated coffee, and the sucrose tasted less sweet afterwards. That's probably due to caffeine's effects — it blocks the brain's adenosine receptors. The researchers thought maybe it blocks adenosine receptors in sweet-sensitive taste buds as well as it did in rodents. "I think the fact that you may be changing how your food tastes if you drink it with coffee is an interesting offshoot of this," said Dando. That means that maybe your chocolate croissant won't taste quite the same if you'd eaten it with a caffeinated drink.
The study had another strange finding. Since the researchers already had a large sample of folks drinking caffeinated versus decaffeinated coffee, they also decided to measure how alert they felt after drinking. It turns out the study participants felt an equal change in alertness, regardless of whether they drank caffeinated or decaffeinated coffee. This could either be due to the placebo effect, or simple conditioning; you're used to caffeine waking you up, so you feel its effects whether or not there's caffeine.
There are limitations to the research; its participants were three-quarters female and almost entirely younger than 40. Additionally, while Dando thought the study's strength was having folks drink coffee, rather than just tasting caffeine, there were other factors they might not have been able to control for. Nor does it control for other things that could potentially affect adenosine receptors, such as anxiety.
I've sent the paper to outside experts for a second opinion. But just imagine, that coffee might change your day in ways different from what you'd expect.