As a neuroscientist who spends much of his working life giving brain talks at events all around the country (at schools, conferences and science festivals) I’ve noticed that one theme catches public imagination over and over again: How does caffeine work? What does it do to my brain? How long does it stay in my system? Is it really that bad for me? This is one reason why it became one of the key topics in the “Smart” Drugs chapter of my book: Sort Your Brain Out. In this blog I’ll cover some of the most regularly asked questions.
How long caffeine takes to leave your system?
It depends what other drugs you’re on. If you’re on the contraceptive pill it can take up to twice as long for your liver to remove caffeine from your system. So people “on the pill” can find themselves particularly sensitive to its effects because consecutive doses stack up and are not cleared out as swiftly as in everyone else. But if you’re a smoker it is the other way around. Caffeine is removed from your system at double the speed of a non-smoker.
If you’re neither a smoker nor on the contraceptive pill the concentration of caffeine in your bloodstream is halved every 5-6 hours, but it really does depend on the individual as this “half-life” varies greatly from person-to-person.
Is it beneficial to have caffeine before a meeting / presentation / to improve concentration?
Caffeine blocks the receptors of an inhibitory neurotransmitter called adenosine, which under normal circumstances reduces overall activity across the brain. By blocking these receptors and removing the dampening influence on brain activity, caffeine increases activity across brain pathways involved in alertness, focusing attention and initiating body movements. This why people dosed up on caffeine can get quite jittery.
Whether or not caffeine is beneficial for you in a meeting / presentation or to improve concentration whilst working depends on how much you’ve already had. There’s a sweet spot where you will feel more alert and switched on at moderate levels, but beyond that you can become so wound up that it has effects that are deleterious to performance (see description of caffeinism below).
However the increase in feelings of alertness and ability to focus attention only gets regular coffee drinkers up to levels enjoyed by non-caffeine drinkers everyday. This is because once you’re a caffeine addict the brain tends to increase the numbers of adenosine receptors to compensate for the fact that there’s loads of caffeine swimming around in your brain on a daily basis. This means that your average coffee drinker has more inhibitory receptors in their brain dampening activity levels to a greater degree – so they will feel more sluggish whenever they don’t have caffeine in their system.
Is caffeine good or bad for you in the long run?
There seem to be some long-term benefits to drinking caffeine even if the short-term benefits don’t amount to a whole hill of (coffee) beans. It has been observed that regular drinkers of moderate amounts of caffeine (3 cups / day) have a lower incidence of Parkinson’s, Alzheimer’s, liver and heart diseases. This may be due to the increased numbers of inhibitory receptors triggered by ever-present levels of caffeine dampening activity levels in body and brain. The decreased activity levels across the brain caused by the larger numbers of inhibitory receptors in the caffeine drinkers’ brains may relieve the pressure on dopamine neurons that are compromised in Parkinson’s disease and the acetyl choline neurons that get clogged up with various proteins in Alzheimer’s disease. In other words caffeine seems to slow down the process of cell death so that symptoms of these diseases kick in several years later than in your average non-caffeine drinker. At the moment this mechanism is purely speculative. The jury’s still out on the precise mechanism that might account for these observations, but the evidence supporting the concept of moderate amounts of caffeine having a neuroprotective influence on the brain is steadily increasing.
Is it important to control and monitor your caffeine intake?
A dose of 10g is deadly – 100 cups and a human may well find themselves popping their clogs as a typical cup of brewed coffee contains 100mg of caffeine. (NB you may notice that in the above video from the lovely people at ASAPscience they say 1 cup of coffee has 150mg – presumably they brew it stronger over in Canada 🙂 For the non-coffee drinkers out there here are some average caffeine contents of some other popular drinks. There are 80mg in a can of Red Bull, 75mg in a cup of instant coffee, 50mg in a cup of tea, 30mg in a can of Coca Cola.
Very high but not deadly doses can lead to a quite severe psychiatric condition known as caffeinism: “which is characterised by restlessness, agitation, excitement, rambling thought and speech, and insomnia.” (Winston et al, 2005). It is important to control and monitor caffeine intake because too much can interfere with appetite, make people anxious or depressed, not to mention the fact that anything that interferes with sleep will have a deleterious effect on the brain. Everyone’s sensitivity to caffeine is slightly different, but if you have trouble sleeping then you’d be well advised to avoid caffeine at least 5-6 hours before bedtime – for your brain’s sake.
3 cups of coffee per day is considered a “moderate dose” for most people. Get these in early enough to avoid any potential for them to interfere with sleep and you should get the apparent long-term brain benefits without the negative consequences associated with excessive consumption (DISCLAIMER: this should not be interpreted as medical advice – it is just the science-based opinion of the author who has a Ph.D. in neurobiology i.e. not a medical degree!).
I don’t like tea or coffee, are there any other sources of caffeine?
Caffeine is also found in kola nut (one of the original ingredients of coca cola) and guarana – a wonder berry from the Brazilian rainforest; it’s also found in low quantities in chocolate. Caffeine is also included as a stimulant in many cold and flu remedies – so beware what you reach for when you wake up in the middle of the night with a bunged up nose!
By the way: if you study the picture on the left very carefully you’ll find a face amongst the coffee beans – can you find it?
Keep looking… he’s definitely there and you’ll kick yourself for doubting me when you find him!!
If you liked this you’ll love my daily brain tweets so please follow me on Twitter by clicking here.