Caffeine: the Fuel of the Modern World
What are the pros and cons of caffeine? Let's take a closer look at the world's favourite drug.
Caffeine is a staple in most people's daily lives. A 2014 study by Mitchell et al found that 85% of Americans consume at least one caffeinated beverage each day, with an average consumption of 165 mg of caffeine daily. Most people's caffeine intake will stem from drinking coffee, though there is also a significant amount of caffeine in energy drinks and tea, and, to a lesser extent, soft drinks.
What is caffeine?
Let's get one thing straight right away: Caffeine is a drug. Technically, it is classified as a "psychoactive drug", a chemical substance that affects "mood, perception or consciousness as a result of changes in the functioning of the nervous system" This is because caffeine is a central nervous system stimulant, and it is most often ingested to prevent or relieve sleepiness or to increase performance.
Caffeine is a natural substance found in the nuts, seeds and leaves of a number of plants. It being naturally occurring does not necessarily make it "good", as cyanide is also found in nature. In fact, caffeine seems to have evolved as a sort of insect repellent for these plants, as insects do not want to eat them. Because humans are hundreds of times the size of bugs, caffeine is relatively safe for human consumption.
How does caffeine work?
There is a chemical compound in your central nervous system called adenosine. This chemical is effectively a byproduct of neurons in your brain. Your brain is constantly working hard when you're awake, and hard work requires a lot of energy. In fact, your brain uses around 20% of your total energy intake, more than any other organ. As the brain works, it creates adenosine, which accumulates in the brain. The more adenosine present, the more tired you feel.
Source: Wikimedia.
1,3,7-Trimethylxanthine, caffeine's chemical name, has a very similar chemical structure to adenosine. This allows caffeine to bind to the same receptors as adenosine, effectively blocking adenosine from latching on to your brain's receptors and making you tired. When caffeine binds to adenosine's receptors, it has the opposite effect on your central nervous system: it increases your brain activity, makes you feel more energised, and less sensitive to your body's natural cycle of wakefulness and sleep.
In turn, this affects other areas of your body. The increased brain activity stimulates the pituitary gland, which activates the release of adrenaline from the adrenal gland. Your liver releases more sugar into the bloodstream for you to consume as energy, your heart beats faster, and your bronchial tubes relax and open up, allowing you to take in more oxygen.
The good
As alluded to above, consuming caffeine essentially flicks the "on" switch in your body and brain by increasing your brain activity and heart rate, among other things. It is therefore obvious that caffeine has a very positive effect on cognitive and physical performance.
Caffeine improves attention, concentration, and motor activity. For example, a typist will be able to work faster and make fewer mistakes after taking caffeine. No wonder coffee is the drink of choice for office workers.
Caffeine is a performance enhancing drug, as it has an ergogenic effect in humans. It can improve sprint performance, has a significant impact on maximal muscle strength and power, and improves muscular endurance. It is rare that a drug has a positive effect on both strength and endurance, so caffeine is almost a miracle drug for athletes or anyone concerned with athletic performance.
Good news for people who suffer from asthma come in the form of researchers showing that even small amounts of caffeine can improve lung function for up to four hours. In fact, some research indicates that caffeine doses of 3-6 mg per kilogram of bodyweight lowers asthma symptoms, and 9 mg per kg can be as effective as some types of asthma medication.
Research also shows that adenosine levels in the blood rise during migraine attacks, and adenosine injected intravenously can even cause migraines. For this reason, caffeine can be part of an effective treatment of severe headaches like migraines.
The bad
Caffeine is not entirely without its drawbacks and risks. It is, after all, a drug. Caffeine may seem addictive, but most researchers today agree that there doesn't seem to be any underlying biomechanical mechanisms for caffeine addiction. While humans can't be "addicted" to caffeine, we can develop a physiological dependence. This means that if you are a regular drinker of coffee, tea or other drinks containing caffeine, you might experience some unpleasant withdrawal symptoms if you suddenly stop cold turkey.
Research by Griffiths and Juliano (2004) shows that common symptoms of caffeine withdrawal include headaches, fatigue, decreased energy, decreased alertness, drowsiness, depressed mood, and irritability, among others. Their research shows that symptoms will start somewhere between 12 and 24 hours after abstinence of caffeine, and can last as long as nine days. Newer research has also established a link between caffeine and anxiety and panic disorders, and high doses of caffeine have been demonstrated to increase anxiety. Enjoying caffeine in moderation might be a good idea for those who suffer from anxiety.
Some researchers argue that caffeine may impact a person's reward system, particularly in children. It is also worth noting that consumption of caffeinated soft drinks, which is what children would most often drink, is associated with poor diet, excess weight, and dental caries, though a direct causative link has not been established.
Among soft drinks that contain caffeine, we find that energy drinks like Red Bull and Monster have around 160 mg of caffeine per 500 ml - around the equivalent of two shots of espresso. What many consumers don't know is that soda also contains caffeine. Coca Cola and Coke Zero contains around 50 mg of caffeine per 500 ml of soda, and Diet Coke contains around 60 mg, with other brands also coming in around the same numbers. Safe to say that one would want to limit a child's access to such drinks, especially considering that caffeinated soft drinks are often marketed towards children. 60 mg might not be much to an adult, but it is a serious amount of caffeine for a child.
The ugly
Most things are lethal if you ingest enough of it. Even water. So it should come as no surprise that caffeine has the potential to be deadly. A toxic dose of caffeine will be around 10 grams, depending on a person's size and their caffeine tolerance level. Considering that an average coffee cup will contain around 100 mg of caffeine, an adult human would have to drink 100 cups of coffee in a single day for this to occur, which seems nigh impossible. It is possible to find pure caffeine powder and caffeine pills though, which would make an overdose much more plausible.
While caffeine is one of the big engines behind the modern workforce, it can also be a very destructive force for your sleep. Caffeine has a half-life of around six hours in adults. This means that if you drink an average cup of coffee at 3 pm, you will still have 50 mg of caffeine flowing through your veins at 9 pm, when your body should be winding down and getting ready for bed. The half-life in infants can be as high as 130 hours(!), with young children presumed to be somewhere in between these figures.
I'm sure we've all heard parents say that their children are on a sugar high after drinking soda. They're not. They're experiencing a big hit of caffeine that will take them many hours to halve. Caffeine's half-life also increases to around 15 hours during pregnancy, according to Dr. Ananya Mandal, meaning that pregnant women should look to moderate their consumption of caffeine rich foods and drinks.
As discussed above, caffeine works by binding to receptors in your brain, and therefore blocking adenosine from attaching itself to these receptors. Adenosine plays a key role in making you feel tired, and winding down the brain before bedtime. Because caffeine stops this natural cycle from starting, caffeine can be very disruptive to your sleep. Not only does caffeine delay your ability to fall asleep, but there is also some evidence to suggest that caffeine inhibits the deep stages of sleep entirely (Mikkelsen, 1978, as cited by Bolton & Null, 1981), with people who don't drink caffeine rich drinks regularly being more sensitive to its sleep depriving effects.
Conclusion
A fresh cup of coffee is the best part of waking up for most people, myself included. There is no shame in that. Caffeine can be very helpful in improving your cognitive abilities in the morning, and throughout the day. There is also a lot of research showing that caffeine has very positive effects on physical performance, so you might find it helpful to have a cup of coffee or a scoop of your favourite pre-workout supplement before working out.
Caffeine isn't without its drawbacks though. It has a big impact on young children, who are more vulnerable to its effects. Some sodas don't contain caffeine at all, while others offer caffeine-free variants. It would be worthwhile to do some research into this topic before serving it to a child. Having big servings of caffeine in the afternoon or evening can also be very detrimental to your sleep quality. This can lead you to waking up feeling tired, which makes you drink more caffeine throughout the day, and the cycle repeats itself.
By all means, enjoy your caffeinated drink of choice guilt free. But try to abstain in the evenings, be careful if you are prone to anxiety, and keep it away from children.
