What caffeine does to your body and brain

• Caffeine has a number of health effects on the body and brain.
• Depending on how you consume it, caffeine could improve memory, boost athletic performance, and be good for the heart.
• But too much of it may also cause irritation or anxiety.

Many of us can't start our day without a jolt of caffeine.

Coffee and tea help people around the globe get through the day, helping us get work done, fueling social interactions, and occasionally offering a quick break from daily pressures.

Various caffeinated drinks affect your health in different ways. Coffee itself seems to be associated with significant health benefits, including reduced cancer risk, improved liver function, and a lower risk for cognitive decline. But other caffeinated beverages like energy drinks have surprisingly high sugar levels, which may have negative health effects but.

But caffeine itself can do a lot, including boost athletic performance, improve memory, and — according to one recent review of studies — it may improve heart function.

The popular stimulant has both positive and negative effects. It makes most of us feel more alert, awake, and focused, but too much can also backfire.

It also affects a host of processes in our bodies, including our digestion, metabolism, and vision. 

Here's what's really going on after you drink a cup of joe.

SEE ALSO: Drinking more coffee is associated with a longer life, according to new research

Caffeine is the most commonly used psychoactive drug in the world.

One of the things rarely mentioned about caffeine is that it is, in fact, a drug. In fact, it’s the most commonly used psychoactive drug in the world, which is probably why we don’t think about it as a drug.

Caffeine has psychoactive effects, and changes the way we feel and interact with the world around us. Yet think of how many of us can’t — or won’t — go through a day without it.

Harvard neuroscientist Charles Czeisler has hypothesized that caffeine, combined with electricity, allowed humans to escape natural patterns of sleep and wakefulness, breaking them free from the cycle of the sun. That change, he wrote in National Geographic, enabled the “great transformation of human economic endeavor from the farm to the factory.”

It makes us feel alert, at least for a while.

It’s normal to grow tired as the day progresses — our brains naturally producemore of a molecule called adenosine from the time we wake up until the time we go to sleep. Scientists think this helps us get to bed at night.

Caffeine hijacks this natural process by mimicking adenosine in the brain. It latches onto the receptors designed for adenosine, pushing them out of the way. As a result, we’re left feeling more alert and awake.

Eventually, however, adenosine wises up to caffeine’s act and makes new receptors for the sleep-inducing molecule to start latching onto again.

This is why your morning cup of coffee can suddenly turn into two — the more receptors you have, the more caffeine you need to plug them up.

One recent review of studies found that caffeine may improve heart function.

Many researchers have assumed that caffeine could potentially cause trouble for people with heart problems like arrhythmias (irregular heart beats).

But a recent review of research found this didn't seem to be the case. Looking at a number of studies with more than 330,000 participants, researchers found that irregular heartbeat frequency decreased between 6 and 13% in regular coffee drinkers. That same review found that people who'd had a heart attack who consumed caffeine (an average of 353 mg per day, or a little over 3 cups of coffee) actually had an improved heart rate and fewer irregular heartbeat issues.

The researchers think that by blocking adenosine, caffeine may reduce heart risks, since adenosine triggers irregular heartbeats.