How Does Caffeine Work?

How Does Caffeine Work?

Caffeine is the most widely used substance on the planet. 

First, a little biology. As your neurons fire throughout the day, a

 neurochemical called adenosine builds up in your body. The 

nervous system uses special receptors to monitor your body’s 

adenosine levels. As the day wears on, more and more adenosine 

passes through those receptors—and it makes you sleepy. It’s one 

of the reasons you get tired at night.  

Caffeine, however, is a stealthy impersonator. It’s the same size 

and shape as adenosine, and when you sip your morning joe, your 

adenosine receptors can’t tell the difference. Specifically, caffeine 

attaches to the A1 receptor. With caffeine docked at the receptor, a 

lot of your body’s adenosine molecules can’t enter. It creates a 

traffic jam of sorts. With all that adenosine blocked, the caffeine 

keeps you from getting tired.

But that’s not where coffee’s kick comes from. With the adenosine 

receptor clogged, neurotransmitters like dopamine and glutamate 

can get a head start. Your dopamine levels swell, giving you a mild 

jolt of energy. In a way, caffeine is like a bouncer. It blocks the 

door, keeping the tired molecules out while the more stimulating 

molecules party on.

But the party can last for only so long. Caffeine may give you that 

much-needed morning boost, but it can also make you crash—hard. 

It takes about four cups of coffee to block half of the brain’s A1 

receptors. With that many receptors clogged, the adenosine 

mounting in your body has nowhere to go. So when the caffeine 

wears off, all that extra adenosine rushes through your receptors. It 

takes a long time for your body to process the huge flow of new 

metabolites. And guess what? It leaves you feeling even groggier 

than you felt before. 

Positive effects of our daily caffeine (coffee/tea) consumption.

Caffeine is a central nervous stimulant and can have some positive 

effects on the human body.

Caffeine in low doses is thought to be associated with an 

improvement in sporting performance, 

increased alertness and reduction in fatigue potentially lifting a 

person’s mood. Coffee and tea also 

contain some antioxidants which have positive effects on heart 

health.

Negative effects of our daily caffeine (coffee/tea) consumption.

However, increased amounts of caffeine lead to dependency due 

to increased tolerance and hence the need for greater amounts to 

gain the same stimulatory benefits. Heavy users who have to go 

without can experience withdrawal symptoms such as headaches 

and fatigue. Too much caffeine can produce restlessness, nausea, 

sleep difficulties, upset stomach, increased urine production 

causing dehydration, and cardiac arrhythmias (irregular 

heartbeats). It has also been associated with elevated blood 

pressure in sensitive persons.

There is no evidence that the effect of caffeine changes with age, 

except that the older you are, the more likely you will be to have 

high blood pressure and heart problems.