Caffeine confidential
I was thinking about Science in the City one morning, when I noticed my wife attempt to put her bike helmet on backwards. I discovered that she was trying to leave for work without her usual mug of coffee.
Each berry on a coffee plant contains two beans.
What’s the buzz?
The key to the buzz is caffeine. It’s the most popular drug in the world, available in various forms, including chocolate, tea, soft drinks and pain relievers. The proportion of caffeine in a roasted coffee bean is half that in a dried tea leaf, but because of the differences in how they’re prepared, a cup of coffee can have twice the caffeine of a cup of tea.
Millions of others world-wide depend on coffee for the buzz that it brings. Every day, on my way to work, I see a lineup of twitching people waiting for their fix at the local dispensary. According to the Coffee Association of Canada, two out of three adult Canadians drink coffee every day, at an average of three cups a day. As a water boy myself, I find this dependence on coffee fascinating.
After my wife has her morning coffee, her body quickly absorbs and circulates the caffeine. Soon she can acknowledge my existence, open the newspaper and form complete sentences. The caffeine has infiltrated her brain and deceived receptors into believing that they are dancing with their usual partner, adenosine, a messenger produced by cell activity. Adenosine tells nerves to slow down, which leads to sleepiness. Caffeine, however, keeps the nerves firing or gets them fired up.
Coffee that tastes like…
Would you pay $600 a pound for coffee? That’s the price of Kopi Luwak, the rarest coffee in the world, made with the help of the palm civet, a mammal the size of a raccoon and related to the mongoose.
It eats the ripest coffee berries, digests the pulpy part, and poops out the beans. In Indonesia, these beans get collected, cleaned and roasted, then sold to coffee fanatics.
Bean there, done that
The two most familiar types of coffee bean are the cheaper robusta variety of Coffea canephora and the more expensive, stronger tasting, yet less caffeinated varieties of Coffea arabica.
This unexpected level of nerve activity is like pulling a biochemical fire alarm in my wife’s brain. In response, her pituitary gland releases hormones that tell her adrenal glands to produce adrenaline. Adrenaline is the “flight or fight” hormone that gets all kinds of systems excited. From her body’s point of view, drinking coffee can be like jumping out of a burning house. The weird thing is that some people who drink decaffeinated coffee, but think they are having regular coffee, experience the same boost as those drinking regular coffee. Go figure.
Also in my wife’s brain, caffeine is raising the level of dopamine, a neurotransmitter involved with the sense of pleasure. You might say she feels like toasting marshmallows in the flames of the burning house. This phenomenon is a mild version of what heroin does. It underlies the addictive nature of coffee.
Why do plants make caffeine?
Caffeine falls into a category of chemicals called methylxanthines. Various plants produce methylxanthines to defend against bugs. I don’t know if spilling coffee on your shirt while camping would keep the bugs away. Try it on your own; it would certainly wake you up.
My wife drinks coffee moderately, but regularly enough to depend on it. If she stops drinking it, she gets a headache. One of the reasons for this is that adenosine makes the blood vessels in her brain dilate which hurts more, whereas caffeine gets them to constrict. At the same time, she says coffee doesn’t stimulate her as much as it used to. Her body’s developed a tolerance to caffeine, as if it can detect a false alarm.
The short-term effects of caffeine vary with the individual and the dose. The long-term effects of it are still unclear. You could try caffeine experiments on yourself or someone you love by recording your own observations and drawing your own conclusions. My wife knows that caffeine is not the best thing for her, but if I’ve learned anything about being married, it’s not to tell her what to do.
This article was first published in February 2003 as part of the “Science in the City” series in The Vancouver Courier.