John Dunsmuir takes us on the journey coffee makes through our body.
Three hundred tonnes of caffeine are consumed globally each year, making it the world’s most popular psychoactive drug. But what makes this insecticide so popular?
The first credible source of coffee drinking comes from Fifteenth Century Sufi monasteries in modern day Yemen. It quickly spread via trade throughout the Mediterranean Basin, entering Europe via Italy.
Caffeine closely resembles the structure of a naturally occuring chemical in the brain known as Adenosine
However, to understand caffeine requires a detailed look at the chemistry of the compound. Caffeine closely resembles the structure of a naturally occurring chemical in the brain known as Adenosine (which itself is produced from the breakdown of ATP in the body). Adenosine receptors in the brain bind adenosine; this is believed to play a key role in regulating circadian rhythms (or sleep cycles). However, due to caffeine’s similar structure, it also bonds to these receptors and blocks adenosine from binding. By doing this, caffeine wards off drowsiness by inhibiting the build-up of adenosine in the brain, thereby disrupting the body’s natural circadian rhythm. For a healthy adult, caffeine is metabolised quickly, with a metabolic half-life of 5.7. After which the adenosine again bonds, causing a caffeine crash. Additionally, with regular caffeine consumption, the number of adenosine receptors increase so larger doses are required over time. However, being awake isn’t the only consequence of caffeine consumption.
To understand further effects requires a look at the breakdown products of caffeine: paraxanthine, theobromine, and theophylline. Each are produced when the caffeine molecule loses a CH3 molecule (known as a methyl group). This means each compound has the same number and type of atoms, but different structures causing different effects on the body.
Beginning with the most common breakdown product at 84%: paraxanthine. Paraxanthine increases fat breakdown; fuelling muscle activity and increasing athletic performance. It is this chemical, over the other two breakdown products, which makes caffeine a popular ingredient in sports drinks.
Secondly at 12% of breakdown products: theobromine, which causes an increased flow of oxygen and nutrients to the brain. This benefits memory retention and cognitive functions, beneficial for completing complex tasks.
Finally, accounting for only 4% of breakdown products: theophylline, which increases heart rate and concentration. This product makes caffeinated drinks dangerous for those with heart problems whilst simultaneously benefitting tired students.
Long-term caffeine consumption also interferes with the production of dopamine, serotonin, and in doses exceeding 500 mg a day, norepinephrine (known as the Happy Chemicals), which can lead to anxiety and depression if over consumed. It is for this reason that 400 mg of caffeine a day (or three to four cups of coffee) is considered the safe limit for consumption. However, this shouldn’t dismay coffee-lovers, as at around 200 mg per day (approximately 2 cups of coffee) any risks are negligible but the benefits to concentration, memory retention, and cognitive functions (such as problemsolving skills) make this a recommended daily amount by some doctors.