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Some things were just made for each other: salt and pepper, peanut butter and jelly, chocolate and…pretty much anything. Alone, these items are just fine, but together, they enhance each other’s best qualities. Nootropics can have similarly beneficial relationships.

The perfect pair of ingredients in a nootropic stack can enhance not only the ingredients’ effects but also the overall cognitive benefits you can enjoy. It’s like a match made in heaven (if you count a bright white laboratory). One such relationship between an amino acid and an alkaloid is like a modern-day Romeo and Juliet romance. But unlike the tragic ending of Shakespeare’s classic tale, the story between L-theanine and caffeine is just beginning.

Spilling the Beans on Caffeine

Before we dive into the sweet synergy between caffeine and L-theanine, we should talk about their best qualities as individuals. We’ll start with the more familiar of the two: caffeine.

Caffeine: America's Nootropic of Choice

Coffee. We were all thinking it because we’re all using it; about 64% of Americans reported drinking at least one cup of coffee every day. But caffeine is found in over sixty other plants, including tea leaves, kola nuts, and cocoa beans.Gilbert1984 Add the synthesized version to these natural sources and you get numerous caffeine-rich foods and medications on the market. You probably know the usual suspects: chocolate, energy drinks, sodas. Even painkillers contain a small dose.

Don’t let that fact keep you up at night; just do a quick scan of the label for any caffeine culprits.

Even if it’s not an essential part of your daily routine, you probably know the basics of caffeine. Caffeine is a crystalline compound that occurs naturally and can be synthesized in a laboratory.

It stimulates the central nervous system in as little as fifteen minutes, providing you with that signature boost.

In order to function as a stimulant, though, caffeine actually has to inhibit certain actions in the brain. As countless neurons fire throughout the day, a neurochemical called adenosine builds up. The build-up of adenosine reduces neuronal activity, which causes you to feel less alert. Because caffeine is the same size and shape of adenosine, it can actually mimic it, preventing it from interacting with neurons and slowing down their activity; this is what gives us that boost.

The Ups and Downs of Caffeine

Even when it’s not in coffee, caffeine is a hot topic. It has many benefits, and consequently, many side effects.

Caffeine may boost your memory,Borota2014 help you power through your strengthAstorino2008 and endurance workouts,Desbrow2012 and even decrease the odds of developing certain types of cancer.Poole2017 But it can also raise your blood pressure,Renda2012 increase anxiety,Rogers2010 and give you a case of the jitters.Shirlow1985 Caffeine is also a diuretic, which will cause you to urinate more frequently to help rid your body of excess water and salt.Reyes2018

An illustration of two cups on a scale, showing the benefits and downsides of using caffeine

Meeting L-theanine for Tea and Coffee

If you prefer to enjoy your caffeine in the form of tea instead of coffee, you’re already familiar with caffeine’s amino acid ally, L-theanine.

The Power Behind L-theanine

L-theanine is a non-protein amino acid that supplies the mouth-filling umami flavor of green tea and black tea.Borzelleca2006

L-theanine can reduce our physiological stress responses by imitating the actions of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that blocks excitatory responses in the brain. L-theanine can also suppress excitatory glutamatergic receptor function. By inhibiting excitatory responses, L-theanine can lower your blood pressure,Rogers2008 heart rate, and stress hormone levels.Kimura2007 Reduce these responses, and you get an overall reduction in stress and anxiety.

While you’re winding down, L-theanine can help your brain generate alpha brain waves associated with relaxing activities such as daydreaming and meditation.Raj1999 Fully relaxed? L-theanine’s prolonged calming effect could edge you that final step toward sleepRaj1999.

L-theanine works on both sides of the sleep cycle. Once you’re awake, you can take L-theanine to start your day focused; human subjects performed attention tasks betterHaskell2008 after supplementing with L-theanine.Dodd2015

L-theanine and Caffeine: The Secrets of Their Relationship

Every great relationship needs a solid foundation to work. And work is exactly what L-theanine and caffeine must do to maintain their caring connection. But hard work is not a guarantee that everything will go as planned. In this section, we’ll explore the couple’s biggest triumphs as well as their biggest obstacles.

Combatting That Stressful Feeling

We know about caffeine’s worst attributes: anxiety, restlessness, increased blood pressure. Like any good partner, L-theanine does its best to correct these qualities for everyone to enjoy caffeine’s company a little more easily.

Caffeine inhibits the actions of our adenosine receptors in the brain, which is the stimulatory activity. L-theanine can help reduce physiological responses to stress by inhibiting excitatory responses in the brain

When these two meet, they don’t just fight each other to stalemate–instead, they work out a compromise.

L-theanine has been shown to allow caffeine to work its brain-boosting charm without letting it raise your blood pressure or induce anxiety.Dodd2015

Caffeine is a vasoconstrictor. These temporarily make blood vessels smaller, which raises your blood pressure to account for reduced blood flow. L-theanine eliminates caffeine’s vasoconstrictive tendencies so you can focus on something other than the sound of the blood pumping in your ears.Dodd2015 If you can’t focus on anything because caffeine crashes leave you with headaches and fatigue, bringing L-theanine along may be able to help; human subjects in a 2008 study reported fewer headaches and less tiredness when mixing the two compared to taking caffeine by itself.Owen2008

A woman biting her pencil, looking stressed at a computer. This show's how L-theanine combats stress.

Calming Down Caffeine

For some, having a cup of coffee after 3pm will keep them up all night. Caffeine can be beneficial or annoying, depending on time of day. L-theanine knows how to calm caffeine down to help attenuate its adverse effects on your sleep schedule.Jang2012

More specifically, L-theanine targets caffeine’s propensity toward reducing your slow-wave sleep, which is the deepest form of non-REM sleep. Getting adequate slow-wave sleep in addition to your REM sleep will result in better overall sleep quality, so you’re less likely to have to rely on caffeine the next day.

Accomplishing Tasks Together

It can be difficult to work with a partner, but caffeine and L-theanine have found their mechanisms. Their groove of working together can be beneficial to help you find your groove.


Like by significantly improving reaction times.Haskell2008 In one study, subjects improved their reaction times for delayed word recognition.Haskell2008 In another, subjects reduced the amount of time it took to respond to flashing light cues on a computer, which suggests an improvement in acute attention.Kahathudawa2017

A man looking at his computed, deep in thought. This shows the benefits of using caffeine and l-theanine to increase attention.

Even switching attention between tasks benefitted from the L-theanine and caffeine stack,Eionother2010 further supporting an overall increase in focus and alertness.Bryan2008 Being able to focus on a task is only half the battle; accomplishing the task well is just as important–and this happy couple can offer their support. In a 2008 study, subjects enjoyed a significant improvement in task accuracy,Haskell2008 while in 2010, the caffeine-theanine induced improvement in task accuracy was reproduced, especially for the most cognitively demanding tasks.Giesbrecht2010

Demanding or not, being able to correctly complete a task only works if you don’t get distracted by a million other stimuli.

Don’t worry; L-theanine and caffeine can reduce your susceptibility to these distractions to really help you hone in on your work.Bryan2008 The combination can work to boost cognitive functionCamfield2014 and overall mental performance for up to six hours. You'll enjoy increased productivity and focusEionother2010 without any jitters, anxiety,Ellis2002 or other negative effects typical of caffeine alone.

Not Always the Perfect Pair

L-theanine and caffeine have done some great things together, but they’re not a perfect couple. Sometimes, they fall out of sync. While many studies have shown promising effects of the dynamic duo, not all research has been able to reproduce the same results.

Take alertness, for example; in some cases, no significant increase in subjective alertness was found.Eionother2010 Similarly, L-theanine and caffeine did not deliver on their natural chemistry in prolonged and monotonous tasks requiring constant attention.Foxe2012 The couple also didn’t show up for mood modifications,Rogers2008 with mood remaining unfazed by their interaction.Haskell2008

Their interaction could be the downfall of their coupling for some; because L-theanine can modulate the stimulatory effects of caffeine, it may be mitigating caffeine’s cognitive benefits.Kakuda2000 The possibility of reducing caffeine’s stimulatory effects could prove even more of a problem for those who are habitual caffeine users because they’ve already lost much of their sensitivity to it.Kelly2008

Synergy Supplementation

Despite their trials and tribulations, this synergistic couple will continue pressing on as research continues. Will they make it? The results are promising.

When supplementing with the duo on a daily basis, you can safely take 100mg - 200mg L-theanine and up to 400mg caffeine, according to the FDA.

L-theanine should not be mixed with medications for blood pressure because it can reduce your blood pressure. Otherwise, L-theanine is not currently associated with any other negative effects or symptoms. Always consult your healthcare professional before starting any new supplements.

A Walk Down Memory Lane

Whether you're looking to increase your cognitive performance or just calm your caffeine nerves, getting ahold of these supplements may be able to help. Caffeine's stimulation and L-theanine's calming support can put you in the ideal mental flowstate, a feeling like you can get anything done.

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