Many of us want (or should I say need?) our morning coffee to give us our “get up and go.”
All told, the people of the world drink more than two billion cups of coffee a day.
You may think that coffee gives you the energy to get through the morning or the day, but coffee may not give you as much as you think.
The main stimulant in coffee is the caffeine. And the main way caffeine works is by changing the way the cells in our brains interact with a substance called caffeine adenosine.
Being busy, getting tired
adenosine is part of the system that regulates our sleep and wake cycles and part of the reason why high activity levels lead to fatigue. As we go about our days and do things, levels of adenosine rise because it is released as a by-product when energy is used in our cells.
In the end adenosine binds to its receptor (parts of cells that receive signals) that tell the cells to slow down, making us feel drowsy and drowsy. This is why you feel tired after a long day of activities. While we sleep energy consumption decreases lowering adenosine levels when it is shaken back into other forms. You wake up in the morning with a fresh feeling. At least, if you get enough sleep.
If you still feel sleepy when you wake up, caffeine may help for a while. It works by binding to the adenosine receptor, which it can do because it has a similar shape. But it’s not so similar that it activates the sleepy delay signal the way adenosine does. Instead, it just fills the spots and stops adenosine from binding there. This is what counteracts the drowsy feeling.
Not a free ride
But there is a catch. While it feels energizing, this little caffeine intervention is more a loan of wakefulness than a creation of new energy.
This is because the caffeine won’t bind forever, and the adenosine that blocks it doesn’t go away. So eventually the caffeine breaks down, releases the receptors and all that adenosine that has been waiting and building up lingers and the sleepy feeling comes back – sometimes all at once.
So the debt you owe to the caffeine always has to be paid back eventually, and the only real way to pay it back is sleep.
Time is everything
How much free adenosine is in your system that hasn’t yet attached to receptors, and how drowsy it makes you, affects how much caffeine you drink to wake you up. So the coffee you drink later on the daywhen you have more sleepy signals, your system can feel more powerful.
If it’s too late in the day, caffeine can make it hard to fall asleep before bed. The “half-life” of caffeine (how long it takes to break down half of it) is approx five o’clock). That said, all of us metabolize caffeine different, so for some of us the effects wear off faster. Regular coffee drinkers may feel less of a “punch” from caffeine tolerance to the stimulus that builds up over time.
Caffeine is also possible increases cortisol levels, a stress hormone that can make you feel more alert. This may mean caffeine feels more effective later in the morning because you already have a natural rise in cortisol when you wake up. The impact of a cup of coffee straight out of bed may not seem as powerful for this reason.
If your favorite caffeinated drink is also a sweet one, it can exacerbate the peak and crash sensation. Because while sugar actually creates energy in the body, the free sugars in your drink can cause a spike in blood sugar, which can make you feel tired when you take the dip comes next.
While there is no proven harm from drinking coffee on an empty stomach, coffee with or after meals can you get slower. This is because the food can slow down the rate at which the caffeine is absorbed.
How about a strong tea or fizzy cola?
Of course, coffee isn’t the only caffeinated beverage that can lend you some energy.
The caffeine in tea, energy drinks and other beverages still has the same effect on the body. But since the ingredients are mostly plant-derived, each caffeinated drink has its own profile of additional compounds that can have their uses own stimulant effector may interact with caffeine to alter its effects.
Caffeine can be helpful, but it’s not magic. To create energy and re-energize our body, we need enough food, water and sleep.
- Emma BeckettAssociate Professor (Food Sciences and Human Nutrition), School of Environmental and Life Sciences, University of Newcastle