Coffee is one of the most popular beverages worldwide. And despite the fact that it tastes bitter and acidic, and makes you poop urgently, without any regard to the availability or proximity of a bathroom, billions of people simply love it and have it every single day, several times a day.
Probably the biggest reason why most people drink coffee is because it helps them stay awake. Coffee is naturally stimulating, that is, it stimulates the nervous system into a physiological state of increased alertness that further correlates with a subsequent rise in motivation and productivity.
Why does coffee keep you awake?
Coffee is a stimulant. Drinking coffee heightens the senses by stimulating the brain and nervous system. Components occurring naturally in coffee actively induce wakefulness. This heightened state of watchfulness translates into increased focus and a measurable boost in motivation and productivity that is felt as elevated energy levels.
According to research, ‘roasted coffee is a complex mixture of thousands of bioactive compounds, and some of them have numerous potential health-promoting properties that have been extensively studied’ (source). Caffeine and theophylline are just two of the many biologically active components occurring naturally in coffee with scientifically-proven and measurable physiological effects.
What is caffeine?
Caffeine is the most studied bioactive compound in brewed coffee. It is classified as a xanthine, purine and alkaloid. It’s a bitter-tasting organic compound partly responsible for the acidity and bitterness of brewed coffee. While it does have the potential for toxicity, as alkaloids generally have after a certain dose, caffeine is also the leading healthful constituent in brewed coffee.
Caffeine is also what makes you stay awake as it’s the primary stimulant element in coffee, with measurable physiological effects on the nervous and cardiovascular systems.
How does coffee keep you awake?
When you drink coffee, the caffeine you ingest travels to the brain. There, it exerts a stimulating effect on the central nervous system. More specifically, caffeine from coffee blocks the normal biological response of adenosine receptors. By blocking adenosine receptors in the brain, caffeine blocks the release of the neurotransmitter adenosine which signals to the body to rest/sleep.
When the adenosine receptors in the brain are blocked and adenosine release is inhibited, there is an automatic counter-effect: glutamate expression increases. Glutamate is a neurotransmitter that has the opposite effect to adenosine: while adenosine is inhibitory and makes the body slow down and rest/sleep, glutamate is excitatory and stimulates the body to be active, awake and alert.
Glutamate as a neurotransmitter fires up nerve cells. So when caffeine in coffee blocks adenosine release, it results in stimulating glutamate release which causes intense nervous system activity, hence the stimulant effects of coffee. Theophylline, another major biologically active constituent in coffee, has the same effect.
When it blocks adenosine receptors, caffeine in coffee also triggers the release of two other neurotransmitters aside from glutamate: noradrenaline and acetylcholine (source). The subsequent release of both noradrenaline and acetylcholine following coffee intake enhances vigilance and increases restlessness which further helps keep you awake and alert, ready for action.
Noradrenaline is the neurotransmitter for alertness and vigilance. It’s released in high amounts in response to stress or danger. Noradrenaline enhances focus, raises blood pressure and heart rate, and prepares the muscles for action. Its a big contributor to keeping you awake and alert.
Acetylcholine is the neurotransmitter that activates muscles – nerve cells communicate with muscle cells via acetylcholine to induce muscle contractions that initiate movement.
But there’s more
Both adenosine and glutamate receptors that are implicated by caffeine and theophylline from coffee in maintaining a state of wakefulness are present primarily in the brain and nervous system. But they exist in other parts of the body too e.g. the heart and the smooth muscles that make up blood vessels.
The presence of the two receptors across the cardiovascular system (heart + blood vessels) is confirmation of the fact that bioactive constituents such as caffeine and theophylline from coffee actively modulate the cardiovascular function.
It’s well known from research that ‘caffeine intake has been associated with a range of reversible and transient physiological effects broadly and cardiovascular effects specifically’ (source). Higher blood pressure numbers, higher heart rate and rhythm are a direct result of drinking coffee and serve to enhance the waking state by increasing alertness.
The stimulation of cardiovascular parameters such as blood pressure, heart rate and heart rhythm are also caused by caffeine (and also theophylline) from coffee blocking adenosine receptors. Caffeine and coffee in general further modulate the gastric function by stimulating the production of stomach juices which is characteristic of wakefulness.
This post was updated on Wednesday / November 17th, 2021 at 9:11 PM