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.
There's a lot of hubbub about caffeine (globally and especially in the U.S.), but how much do we actually know about this phytonutrient and how the unique plant compound works? What is that alertness we feel after consuming a cup of coffee? Is it actually energy, or is there more to the story here? Well, we've asked some experts, and they have the answers.
Does caffeine give you energy?
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.
But Crouch highlights what caffeine's energizing reputation is truly rooted in: "By stimulating excitatory neurotransmitters, it jump-starts the brain the way that adrenaline does, which sends messages to the rest of the body to perform."*
More on how caffeine affects the brain.
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.
Unfortunately, at some point, that caffeine will give way to adenosine and—*crash,* you've hit that dreaded the 3 p.m. slump. But as Ferira alluded to before, that slump scenario is, of course, if you're relying solely on instant-release caffeine rather than a strategic mixture of instant- and sustained-release caffeine sources. Such a combo can thankfully be found in innovative supplements, like mbg's focus+.
The bottom line: Is caffeine worth the hype?
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.
So, whether you define energy as feeling more alert or prefer its more technical nutrition definition of fueling molecules and cellular pathways with ATP, caffeine can be an effective way to deal with our often demanding world. And like anything else, caffeine balance is critical—not too much, not too often, and always paired with some actual energy in the form of calories from nutrient-dense food.
Josey Murray is a freelance writer focused on inclusive wellness, joyful movement, mental health, and the like. A graduate of Wellesley College, where she studied English and Creative Writing, her work appears in Women’s Health, Cook & Culture, and more. By expressing her own vulnerability, she writes with warmth and empathy to help readers find self-compassion and true wellness that’s sustainable for body, mind, and planet.