How Exactly Does Caffeine Deliver Its Energizing Effects? Experts Explain

Caffeine is one of those things that just makes life easier—especially on days when you can't seem to snap out of a funk or the morning after a work deadline, a noisy neighbor upstairs, or a little one who needs some love keeps you up until the late hours of the night.

Some claim that caffeine doesn't give you energy, it just makes you forget that you're tired. So, what's the deal with this minor distinction? Well, it seems to be mostly semantic. Nonetheless, this distinction and difference may speak to our misunderstanding of exactly how caffeine interacts with our physiological systems (and how it's seemingly been energizing the human race for, well, thousands of years). 

"[Caffeine] does indeed have the ability to maintain alertness when one would otherwise be tired, and it increases behavior in many cases,"* says Matthew W. Johnson, Ph.D., professor in psychiatry and behavioral sciences at Johns Hopkins.

"You can call that energy, but there will certainly be a rebound effect when dealing with meaningful doses. So, you can say it increases energy in the short term at the expense of the long term, to a degree,"* he explains.

Indeed, "the cognitive and physical energy is a temporary gift that instant-release caffeine gives,"* shares Ashley Jordan Ferira, Ph.D., RDN, mbg's vice president of scientific affairs. She goes on to explain that, "there is also heightened potential for experiencing the caffeine 'crash' phenomenon, or rebound effects, with instant-release caffeine."

But as it turns out, extended-release caffeine exists. "These sustained caffeine release profiles leverage novel absorption technology1 to level out the increased caffeine levels in your body, leading to longer efficacy, minus the dreaded crash,"* says Ferira. That sounds like the best of both worlds, if you ask us.

In the case of nutrition (i.e., where calories define metabolic energy), caffeine doesn't provide that type of nutrition 101 textbook energy at all. "Despite what it may feel like, consuming caffeine does not increase cellular energy production (ATP) or provide fuel (i.e., protein, fats, carbohydrates) for muscles to perform," shares integrative registered dietitian Whitney Crouch, RDN, CLT.

So if the "energy" we feel from caffeine doesn't come from fuel molecules or ATP, how do its effects on the central nervous system support that energizing feeling that our coffee or tea (so lovingly) offers us?

"[Caffeine] reduces the activity of a neurotransmitter called adenosine, which is responsible for putting the brakes on other neurotransmitters that have an excitatory or stimulant effect. The net effect is increased stimulation,"* shares Johnson.

Essentially, adenosine builds up as you're awake and attaches to its receptors on brain cells later in the day (and through the night) to slow them down, making you feel sleepy. Caffeine competes with the latter from happening by taking adenosine's place and binding to its receptors2. 

This antagonistic interaction with adenosine receptors also allows for the release of excitatory neurotransmitters—such as glutamate, norepinephrine, acetylcholine, dopamine, and adrenaline—by blocking inhibitory chemicals, Crouch adds. 

While caffeine doesn't give you energy in the traditional (food equals ATP) sense of the word, there's no doubt that it makes you feel more alert and energized.* 

"Indeed, research outcomes including increased alertness3, concentration4, productivity, mood balance5, and even creativity6 (so cool!) are clearly and repeatedly borne out in the published science for caffeine thanks to its adenosine-dampening actions,"* concludes Ferira.

And according to Johnson, the benefits of caffeine—which include powerful mental stimulation, feeling more wakeful and alert, and even enhanced athletic performance—are best experienced when it's consumed at "judiciously chosen times."* 

Plus, we can't forget that some sources of caffeine (e.g., whole coffee fruit7, i.e., the coffee "berry" or "cherry," interchangeable terms) offer a healthy dose of polyphenolic antioxidants and promote oxidative balance throughout the body.* 

And as it turns out, "caffeine itself has antioxidant properties8, so while it might be famous for energizing us daily, it's not all about energy. This is a truly fascinating plant compound,"* shares Ferira.