Morgan Chamberlain

mbg Supplement Editor

By Morgan Chamberlain

mbg Supplement Editor

Morgan Chamberlain is a supplement editor at mindbodygreen. She graduated from Syracuse University with a Bachelor of Science degree in magazine journalism and a minor in nutrition.

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Image by Alberto Bogo / Unsplash

April 8, 2023

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Whether you make your own pour-over, head to your local coffee shop for matcha, or enjoy a midday tea, caffeine is an integral part of many people’s days. When you’ve got things to do and places to be, the energizing effects of caffeine can be a lifesaver. The benefits of caffeine aren’t limited to energy, though. Ahead, learn about its effects on the body and mind (from brain health to athletic ability) plus how to tell you’ve had too much.


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What is caffeine and how does it work?

Caffeine is a unique phytonutrient compound (or sometimes, a synthetic substance, depending on the source) that stimulates the central nervous system (CNS).* As a plant nutrient (aka phyto + nutrient), it’s naturally found in more than 60 plants1, including coffee berries, coffee beans, tea leaves, guarana seeds, and cacao beans (i.e., chocolate).

In the body, caffeine sources like espresso and coffee stimulate your CNS (i.e., your brain and spinal cord) primarily by blocking adenosine receptors2, according to Isa Kujawski, MPH, RDN, registered dietitian nutritionist and founder of Mea Nutrition.*

A quick explainer: Adenosine is a neurotransmitter, aka a chemical messenger secreted by nerve cells (neurons). When it binds to specific receptors, adenosine slows down neural activity and makes you sleepy. Your levels of adenosine naturally increase the longer you’re awake and drop while you snooze at night.

However, caffeine has a similar structure to adenosine—so much so that it can swoop in and bind to adenosine receptors.* It’s a natural “antagonist” (turns out to be a useful thing) of the receptor. This temporarily prevents adenosine from attaching to said receptors, helping you feel more wakeful and alert.*

Benefits of caffeine.

Here’s what caffeine can do for your body and mind, according to experts and research: 


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1. Supports focus and mental clarity.

In addition to blocking adenosine receptors, caffeine also activates the pituitary gland to make some adrenaline, says Kujawski. (Adrenaline is known as the “fight or flight” hormone, btw.) 

“This mimics our normal stress response, which increases our attention levels and gives us a burst of energy and alertness,”* explains Kujawski.

“Caffeine also indirectly stimulates the release of neurotransmitters such as dopamine, serotonin, and GABA,”* she adds. These “feel-good” neurotransmitters can help maintain attention3 and focus, making it easier to tackle your to-do list. 


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2. Helps support memory.

According to a 2021 review in the journal Nutrientslow doses of caffeine can improve memory and cognitive performance, which may be due to its ability to bind to adenosine receptors (which also promotes dilation of blood vessels via nitric oxide pathways for blood flow to the brain), as well as its neuroprotective benefits4.* 

However, as a 2021 review in Neuroscience & Behavioral Reviews notes, caffeine’s effects on memory5 might vary depending on individual demographics (i.e., age, sex, and caffeine metabolism rate) and memory type.

While more research will be useful to tease apart these personalized nuances more, clinical literature to date demonstrates caffeine’s beneficial impact on both short-term and long-term memory6 in young and older adults.

3. Neutralizes free radicals.

Did you know that caffeine has antioxidant properties7? “As with other antioxidants like vitamin C and resveratrol, caffeine has [the] ability to protect against free radicals,”* shares Ella Davar, R.D., CDN, registered dietitian and founder of Nutritionist Ella

Again, this brings us full circle to caffeine being a plant nutrient (phytonutrient), which often serves up antioxidant actions. This, of course, assumes your caffeine source is plant-derived, for example from a whole coffee cherry8 extract.

Caffeine’s antioxidant characteristics help enhance our antioxidant defenses (i.e., combating and balancing free radicals), which in turn, promotes whole-body health.* In fact, according to a scientific review in Skin Pharmacology and Physiology9, these benefits even extend externally to the skin, where caffeine’s antioxidant actions (i.e., in topical applications) can delay signs of aging.


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4. Promotes multidimensional brain health.

The antioxidant abilities of caffeine also nurture our brain.* Regulating oxidative balance10, after all, is essential for supporting healthy nerve cells and brain function. According to a 2020 scientific review11 from the Saudi Pharmaceutical Journal, caffeine also mitigates neural pathways and protects neurons, ultimately promoting overall brain wellness.*

As Ashley Jordan Ferira, Ph.D., RDN, mbg’s vice president of scientific affairs explains, “Caffeine is actually multitasking on our behalf when it comes to brain benefits. Research demonstrates its multidimensional abilities to sustain attention and improve alertness12, enhance problem solving and creativity13, fuel mental alertness14, and even elevate mood15.”*

Ferira further explains that, “with the right caffeine matrix (i.e., delivery technology), certain sustained caffeine ingredients from the Coffea plant species (coffee) have been shown to net an especially impressive array of productive brain benefits14 in the alertness and mood arenas while simultaneously combating the converse effects like mental tiredness, dip in mood, and jitters.”* (You know, that no-so-fun caffeine “crash” phenomenon.)

5. Bolsters exercise performance.

Whether you’re training for a marathon or hitting up a HIIT class, caffeine is considered a stimulating ergogenic acid that can elevate your routine, physical energy, and performance.*

“Caffeine activates neural circuits and, in turn, the release of adrenaline,”* explains Kujawski. This dilates blood vessels and air passages, which increases blood flow and oxygen to your brain and muscles, she says. This effect, along with the energizing effects of caffeine, can help enhance overall athletic performance.*


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Sources of caffeine.

When it comes to the most common sources of caffeine, the amount in each serving can vary widely. It depends on many factors, including preparation technique and brewing time.

For example, the caffeine content of coffee beans depends on how long they’ve been roasted. Likewise, the longer black tea leaves are steeped, the more caffeine your tea will have. 

Here’s how much caffeine you can find in common sources, according to validated nutrient analysis data16:

You can also consume caffeine in supplements, either on its own or combined with other nootropic ingredients. The latter multi-ingredient design can be especially beneficial, given you pick a formula that supports overall brain power and goes beyond the typical (and transient) energy “boost” approach.

For example, in mbg’s focus+, caffeine is paired with bioactives and botanicals that support the energy of cells, mind, and body (i.e., guarana, Panax ginseng, L-theanine, and vitamin B12), resulting in sustained focus and vitality.*

Just like with the food and beverage sources of caffeine listed above, it’s also important to carefully consider your caffeine source when it’s delivered in a supplement.

Ferira advises turning the product over and reading the Supplement Facts panel: “Do you see any indication that the caffeine is derived from a plant source, like a specific species of coffee (Coffea), tea (Camellia), guarana, or some other quality-sourced plant?” If not, she says it could be the cheaper synthetic variety of caffeine instead.

Sharing further intel, Ferira explains that, “you should also expect the supplement brand to identify the plant parts used to provide the caffeine. In other words, is this an extract of the whole coffee cherry8, the coffee beans, or green tea leaves? Transparency is key here.”

Forms of caffeine.

In addition to the sourcing info, there are two main forms of caffeine in terms of its speed of delivery and action: instant release and extended release1414. The type of caffeine determines how quickly you absorb it and your caffeine plasma (blood) levels rise, and then ultimately, how it affects you.

Typically, caffeine is consumed as instant-release caffeine. This form can be found in food, drinks, and supplements. It’s rapidly absorbed by the body, leading to increased caffeine plasma levels that can drop as quickly as they rise. (Hello, caffeine crash!)

Extended-release caffeine, also called sustained-release caffeine, is considered cutting-edge, science-backed technology14. It’s found in innovative supplements like mbg’s focus+ (along with instant-release caffeine, so you get focused energy benefits immediately and throughout the day).* This unique type of caffeine from green coffee beans is specially designed (and clinically shown14) to slowly release over several hours, resulting in a steady flow of energy and cognitive gains.*

As Ferira explains, not only is sustained-release caffeine novel, but it’s also next-level when it comes to efficacy in our brain and body. “The sustained-release Xtenergy caffeine that’s provided in focus+ leverages absorption technology to extend the caffeine release profile14 and timeline beautifully,” she shares. “It’s like smoothing and balancing out the caffeine curve and avoiding spikes in blood levels of caffeine, and thus, precipitous drops on the way down,” Ferira adds.

And thankfully all this fancy science results in practical, enhanced benefits for alertness and mood14 while buffering against the infamous caffeine crash.*

Side effects of caffeine.

First, it’s worth noting that caffeine affects everyone differently. “Such an individualized response is quite common for botanical bioactives,” Ferira explains.

Indeed, we all metabolize caffeine at variable rates24. “From age and sex to body composition, diet, hormones, the all-important genetic variation at the level of our CYP1A2 metabolism gene, and more—we are caffeine unique!”

So, depending on the dose and person, caffeine may produce variable effects (in terms of positive benefits and efficacy) and on the flip side, contribute to certain side effects:

Jitters. As caffeine increases adrenaline, it can make some people feel jittery, shaky, and restless. This is especially true when instant-release caffeine is not combined with its sustained-release partner (which has been shown to combat jitters14 and other crash manifestations). Jitters can make it difficult to relax, especially if you take it close to bedtime.

Caffeine crash. It takes just 15 to 60 minutes for the body to absorb instant-release caffeine, says Davar. Without sustained-release caffeine present14, this rapid absorption can decline just as quickly, causing the dreaded afternoon energy crash in some people.

Diuretic properties. Caffeine increases blood flow and filtration in the kidneys2, which increases urine production. In other words? You may find yourself making extra trips to the restroom.

How much caffeine is too much?

For the average person, it’s recommended to consume no more than 400 milligrams of caffeine per day, per the FDA25. That’s equal to approximately four 8-ounce cups of brewed coffee. However, if you’re sensitive to caffeine, your threshold will likely be lower.

“While 400 milligrams has demonstrated safety in healthy adults thanks to scientific research26, 200 to 300 milligrams is a more conservative daily limit that’s considered a prudent approach for women who are pregnant27 or trying to become pregnant,” shares Ferira.

It’s also a good idea to consider your timing. According to Kujawski, caffeine can take up to 10 hours to completely wear off, so you should stop consuming it at least 10 hours before bedtime. (But again, everyone processes caffeine at different rates, so be sure to listen to your body.)

You should also make an attempt to reduce your caffeine intake if you start feeling uneasy, restless, or have physical discomfort in your head or chest. This might be your body trying to tell you that you’ve consumed too much caffeine.

Be mindful of your long-term consumption of caffeine, too. Over time, ingesting high amounts can mess with your sleep schedule, says Kujawski. Excessive amounts of caffeine can also affect your stomach, heart, and nervous system, so you’ll want to enjoy the ingredient in moderation. If you’re sensitive to caffeine, talk to your health care provider before consuming the ingredient in any form.

The takeaway.

Caffeine stimulates the central nervous system by interacting with key neurotransmitter receptors and increasing vasodilation—these neuromodulatory pathways increase energy levels while promoting focus, alertness, mental clarity and concentration, cognitive and physical performance, and more.* Caffeine also has intrinsic antioxidant properties, which nurtures brain and whole-body health.*

To feel more focused throughout the day, consider adding moderately dosed caffeine sources, whether coffee and tea or a complementary nootropic supplement to your wellness routine.* When it comes to supplements with caffeine, the key is to choose a formula with plant-origin ingredients that support multiple aspects of brain power while providing sustainable energy rooted in science (like mbg’s focus+).*

If you are pregnant, breastfeeding, or taking medications, consult with your doctor before starting a supplement routine. It is always optimal to consult with a health care provider when considering what supplements are right for you.