Despite thousands of years of caffeine consumption, it is only in the last 60 years that we have started to understand how it works to give us these glorious effects.
In the UK, we now drink approximately 98 million cups of coffee per day! But how much do we know about the coffee we are drinking?
I am not just talking about its origins, production or impact on the environment. I am talking about why it works and how it keeps us alert. How much do we know about caffeine, the most popular psychoactive drug in the world? Is there an optimal time to drink coffee? How much is too much? How is it impacting your body?
How does coffee work
As the brain uses up energy throughout the day the by-product is adenosine. As we go through the day, adenosine rises. Adenosine is responsible for the sleepy feeling, hence the longer we are awake the sleepier we feel.
High adenosine levels in the brain indicate the brain has been very active and needs to rest. Caffeine works by blocking our adenosine receptors, in turn stopping the adenosine making us sleepy. This is how caffeine makes us feel more alert, but how does it lift our mood?
Some adenosine receptors are linked to dopamine receptors, dopamine is the chemical that makes us feel ‘happy’. When the adenosine uses the receptors it makes it harder for the dopamine to use them, so we get less of this ‘happiness’ hormone. Caffeine enables the paired dopamine/adenosine receptors to focus on the dopamine by blocking the adenosine from using the receptors.
Adenosine receptors are also found in the heart and kidneys. When adenosine activates these receptors it decreases their activity slowing down the heart and urine production. This is a way to give these organs a rest, as with the brain. When these receptors are blocked by caffeine the opposite occurs, heart rate increases and more urine is produced.
How does this affect us?- The good, the bad and the unknown
The caffeine love
Caffeine makes us feel more alert by blocking the adenosine receptors in turn telling us it’s time to rest by slowing us down. It lifts our mood by enabling more dopamine. This positive effect of caffeine makes us love it and become dependant on it. On the other hand, over alertness leads to headaches and dizziness, increased heart rate to jitteriness and increased urine production to dehydration.
In short, it makes you feel more alert, happier and energised but it also increases your blood pressure, heart rate, stress hormones cortisol and adrenaline and causes increased urination or diarrhoea.
The caffeine crash
The effect of caffeine only lasts for two to four hours depending on your sensitivity. While you are under the glorious effects of caffeine, your adenosine levels are still rising. When the caffeine starts to wear out, your receptors are ‘unblocked’ and the adenosine floods in. Resulting in an energy ‘crash’ like effect.
Increased caffeine tolerance
As your adenosine receptors are not able to be used by adenosine, your body can create more adenosine receptors. Over time you need to consume more and more caffeine to stay alert, as you need more caffeine to block the extra receptors your body created.
The caffeine withdrawal
Our bodies become physically and psychologically dependent on caffeine. When we cut it out we may experience; headaches, anxiety, irritability, low mood, tremors, difficulty concentrating. The increased adenosine receptors help us understand some of what is going on when we experience caffeine withdrawal.
It is encouraging to note it only takes a few days without caffeine for the body to adjust and reduce the number of receptors although the withdrawal symptoms may last longer. Often without us noticing withdrawal symptoms cause us to drink more caffeine to counteract them leading to a mild dependence on caffeine
How much caffeine?
After 200mg (2 cups) of coffee, you do not get any extra benefits from coffee. If 200mg was not enough for you to wake up, focus or feel better then you need a nap. After 200mg of coffee, you start to experience more of the negative effects of caffeine. Over the long term, this leads to increased burnout, depression and anxiety.
When to have your coffee?
One of the challenges we have with caffeine impacting our sleep is that it has a half-life of 6-7 hours. Six to seven hours after you consume caffeine half of it is still in your system even though the bulk of its positive effects have worn out. This makes caffeine's quarter-life 12 hours. If you have a cup of caffeine at noon, it is equal to drinking a quarter cup of coffee at midnight, or the equivalent of an English breakfast tea (black tea) before you go to bed. As a result, you wake up feeling less refreshed and increase the amount of caffeine you drink.
Needing to drink coffee soon after you wake up maybe an indicator you are not sleeping well at night. Having caffeine after midday will certainly impact your nighttime sleep. My current aim is to keep my caffeine consumption before midday and try to drink decaf. Unfortunately, that means watching the red bulls, coke, energy drinks and coffee when we need it the most or on nights out. Don’t despair because a 20min nap can give you the same benefits as your caffeine hit with none of the side effects.
Caffeine is a sleep disruptor - but it doesn't affect me
Many people claim they can drink caffeine before bed and it doesn’t impact their sleep. More studies are finding out how it impacts our sleep and how oblivious we are to this impact. Caffeine impacts our sleep quality, how long it takes for us to fall asleep and increases the amount we wake up at night. One study shows, on average when people had a cup of coffee at 7 am it took 20 minutes longer to fall asleep at night and they woke twice as much compared to when they didn’t drink coffee. As a result, they woke up less refreshed the next day.
‘One dose of caffeine in the evening decreases the amount of deep sleep by about 20%, that's equivalent to aging 15 years to have that type of impact on your sleep. ‘ Matthew Walker
Those that say that coffee doesn't affect them may be oblivious to the impact. As the study mentioned suggests as well as this ad hoc antidote from Dr Amy Benders research. In a study looking at quitting smoking, the sleep architecture of one individual who drank a cup of coffee before bed and claimed it didn’t impact them showed they woke up 22 times per hour without realising. This was double the amount than when they didn't drink caffeine.
Try it, cut out your caffeine and see if after the withdrawal period your sleep improves.
But I Love my coffee
As the saying goes, ‘everything in moderation'. I love my coffee too and there is a better way we can enjoy our coffee that has less of an impact on our sleep. There are a lot of other health benefits linked to coffee, so maybe cutting it completely out isn't the purpose. Here are some ideas you can consider incorporating into your life. For most of us, cutting down caffeine can potentially make our productivity go up.
‘Drink caffeine strategically, not automatically.’ Dr Amy Bender
Drink caffeine only a few hours into your day, having your coffee after midday will certainly have some impact on your sleep
Caffeine detox -Introduce days where you have no caffeine to minimize your caffeine dependency.
Drink decaf - although decaf is not actually uncaffeinated it has significantly less caffeine.
Caffeine should NOT be used to avoid sleep - Don’t drink caffeine to keep yourself up for longer, (unless you are working a night shift of course). In a few hours time when you are ready to hit the hay, the caffeine will be playing against you. Adequate sleep is required for the brain, heart, kidneys and body to rest and recuperate, adenosine is our indicator the brain and body needs to rest.
Weaning yourself off caffeine gradually is a good way to avoid heavy withdrawal symptoms. Be Careful not to replace it with sugars and other stimulants.
Children shouldn't drink caffeine as the effects of caffeine on a developing brain are currently unknown.
There are some benefits and side effects of coffee that are still apparent even when someone consumes decaf coffee. This indicates there is more going on here with coffee that we are yet to understand.
Decaf coffee is processed and a lot of nutritionists as a rule of thumb recommend we avoid processed foods. There are no harmful effects of decaf coffee known to us currently, subsequently there is not much research into it. Some methods of decaffeinating coffee require chemicals and others are more ‘natural’ using purified water techniques. Decaffeination methods have been around since 1905 but the jury is still out on whether it is ‘healthy’. A common stance is everything in moderation, copious amounts of a good thing can make it bad for you.
Enjoy your coffee strategically, replace your need for it with good sleep and great naps!