L-Theanine and Caffeine: A Powerful Duo for Health and Wellness

L-Theanine and Caffeine: A Powerful Duo for Health and Wellness

The combination of certain compounds can yield remarkable benefits for health. One such combination that has gained attention in recent years is that of L-Theanine and caffeine. L-Theanine, an amino acid found primarily in tea leaves, and caffeine, a well-known stimulant found in coffee, have been studied for their individual effects on cognition, mood, and overall health. However, when combined, they appear to offer unique advantages that go beyond what either compound can provide alone.

In this article, we delve into the scientific evidence behind the synergy of L-Theanine and caffeine and explore the potential health benefits of this powerful duo.

Spilling the Beans on Caffeine

Caffeine is a naturally occurring compound in various plants, including coffee beans, tea leaves, and cacao pods. It belongs to a class of compounds known as methylxanthines and is one of the most widely consumed psychoactive substances in the world. The primary mechanism of action of caffeine involves its interaction with adenosine receptors in the brain.

Adenosine is a neurotransmitter that plays a role in regulating arousal, sleep-wake cycles, and vasodilation (the widening of blood vessels). Throughout the day, adenosine levels gradually increase in the brain, leading to feelings of drowsiness and promoting sleep.

Caffeine structurally resembles adenosine and competes with it for binding to adenosine receptors. However, unlike adenosine, caffeine does not induce feelings of drowsiness or relaxation when it binds to these receptors. Instead, caffeine acts as an antagonist, blocking the action of adenosine. By occupying adenosine receptors, caffeine prevents adenosine from exerting its inhibitory effects on neurotransmitter release.

One of the primary consequences of caffeine's blockade of adenosine receptors is the promotion of wakefulness and alertness. By inhibiting adenosine's sleep-inducing effects, caffeine increases neuronal firing in the brain and stimulates the release of other neurotransmitters, such as dopamine, norepinephrine, and acetylcholine. These neurotransmitters are involved in various physiological processes, including arousal, attention, mood, and cognitive function.

However, caffeine is a double-edged sword. While it may enhance memory and improve workout performance, it can also cause high blood pressure, increase anxiety, and cause jitters. It's a diuretic, too, making you urinate more frequently to eliminate excess water and salt from your body.

Benefits of Caffeine

  • Increased alertness and wakefulness
  • Enhanced cognitive functions
  • Mood improvement
  • Improved physical performance
  • Metabolic boost
  • Antioxidant properties

What is L-Theanine?

L-Theanine, a naturally occurring amino acid, is a hidden gem found in your daily cup of tea or coffee. This compound has been linked to a range of health benefits, from reducing stress responses to enhancing cognitive function. It's a powerful ally to caffeine, the stimulant we often rely on to kickstart our day.

It mimics the actions of gamma-aminobutyric acid, an inhibitory neurotransmitter that blocks excitatory responses in the brain. By suppressing excitatory glutamatergic receptor function, L-Theanine can effectively lower blood pressure, heart rate, and stress hormone levels, leading to an overall reduction in stress and anxiety.

L-Theanine also aids in generating alpha brain waves, which are associated with relaxing activities such as daydreaming and meditation. This prolonged calming effect can help you transition from a state of relaxation to sleep. Moreover, L-Theanine can also enhance focus and attention once you're awake, making it a valuable tool for starting your day on a positive note.

Despite these promising findings, it's important to note that everyone's response to L-Theanine can vary based on individual factors. Therefore, it's always advisable to consult with a healthcare provider before incorporating L-Theanine into your health regimen.

Benefits of L-Theanine

  • Promotes relaxation without drowsiness
  • Reduces stress and anxiety
  • Enhances cognitive function
  • Improves focus and attention
  • Supports better sleep quality

The Benefits of L-Theanine and Caffeine Together

Combining L-Theanine and caffeine can create a synergistic effect that enhances the positive aspects of both while mitigating potential negatives.

Synergistic Effects

L-Theanine's calming effects are a perfect counterbalance to the stimulating effects of caffeine. This calming effect is attributed to L-Theanine’s influence on increasing levels of neurotransmitters like GABA, serotonin, and dopamine, which are associated with mood, relaxation, and stress reduction.

The compound also modulates the activity of the excitatory neurotransmitter glutamate. By doing so it helps counterbalance the jitteriness, anxiety, and potential overstimulation that caffeine can cause, smoothing out the energy boost without dampening the cognitive benefits of caffeine.

This synergy allows individuals to enjoy heightened alertness and concentration from caffeine with fewer undesirable side effects such as nervousness and subsequent energy crashes.

Improved Cognitive Performance and Increased Focus

L-Theanine has been shown to mitigate some of the adverse effects of caffeine. However, it doesn't interfere with caffeine's positive impact on cognitive performance. In fact, some studies suggest that the combination of L-Theanine and caffeine can enhance attention and other aspects of cognitive function.

A systematic review conducted by Sohail et al. (2021) found that combining caffeine and L-Theanine improved short-term sustained attention and overall cognition. It also reduced mind-wandering and improved inhibitory control among boys with attention deficit hyperactivity disorder (ADHD). The researchers found the combined effects of L-Theanine and caffeine can help manage the cognitive deficits associated with ADHD.

A functional magnetic resonance imaging study by Kahathuduwa et al. (2020) confirmed that the administration of a combination of 2.5 mg of L-Theanine and 2.0 mg of caffeine may result in short-term improvements in sustained attention and overall cognition composite of NIH Cognition Toolbox (a set of seven cognitive function tests) among boys with ADHD, possibly by decreasing mind wandering associated with ADHD.

The benefits of this combination extend beyond just improving focus. Giesbrecht et al. (2010) conducted a placebo-controlled study evaluating the impact of the L-Theanine caffeine combination on cognitive performance and subjective alertness. They discovered that 97 mg of L-Theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task. It also improved accuracy and self-reported alertness and reduced self-reported tiredness.

By mitigating the side effects of caffeine, such as jitteriness and eventual energy crash, the combination of L-Theanine and caffeine allows for longer periods of concentration and productivity. For example, a study found that the combination has been shown to boost cognitive function and overall mental performance for up to six hours. This can lead to increased productivity and focus without the jitters, anxiety, or other negative effects typically associated with caffeine alone.

Better Sleep Quality

L-Theanine has a knack for calming caffeine's hyperactivity. It targets caffeine's tendency to reduce slow-wave sleep, the deepest form of non-REM sleep. By ensuring you get enough slow-wave sleep, L-Theanine helps improve your overall sleep quality, reducing your reliance on caffeine the next day. It also curbs caffeine's vasoconstrictive tendencies, which can raise your blood pressure and cause anxiety.

In a controlled study, Baba, Takihara, and Okamura (2023) found that taking L-Theanine reduces the excitotoxicity of caffeine and improves the sleep quality worsened by caffeine in healthy young women. An earlier study supported the idea that L-Theanine blunts both caffeine’s blood-pressure-increasing effects and its sleep-disrupting effects, which is why L-Theanine is recommended for treating sleep disturbances.

Anxiety and Stress Relief

When combined, L-Theanine counteracts the potential negative effects of caffeine, such as anxiety and increased heart rate, while preserving its cognitive-enhancing benefits. L-Theanine increases alpha brain waves, leading to a state of calm alertness and potentially lowering stress levels.

In a study by Yoto et al. (2012), L-Theanine not only reduces anxiety but also attenuates the blood pressure increase in high-stress-response adults. In a later placebo-controlled clinical trial, Hidese et al. discovered that L-Theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.

This was confirmed by Ritsner et al. (2011), who found that L-Theanine relieves anxiety symptoms and positive activation in patients with schizophrenia. The researchers' 8-week randomized placebo-controlled study is very promising in showcasing the benefits of L-Theanine; however, despite the preliminary evidence presented, further research is needed to understand the synergistic effects and therapeutic efficacy of L-Theanine and caffeine and their broader implications for anxiety disorders.

How to Take L-Theanine and Caffeine

To harness the benefits of L-Theanine and caffeine, it's essential to consider dosage, timing, and method of consumption. Typically, L-Theanine is taken in doses ranging from 100 mg to 200 mg, while caffeine doses can vary from 50 mg to 200 mg. The optimal ratio between L-Theanine and caffeine is often around 1:1 or 2:1, ensuring a balanced combination that maximizes their synergistic effects.

It's recommended to take them together for optimal results. NMN Bio's NAD+ Brain includes 100 mg of L-Theanine and 50 mg of caffeine per serving. This blend cultivates a balanced synergy, fostering serene focus without unwanted jitters, making it an attractive choice for those pursuing enhanced cognitive function.

Starting with lower doses is advisable, especially for those new to the combination, to gauge individual tolerance and response, gradually adjusting as needed. Personal factors such as body weight, caffeine sensitivity, and overall health should also be considered when determining the ideal dosage.

While L-Theanine is generally well-tolerated, caution should be exercised regarding caffeine intake to avoid potential side effects such as jitteriness or insomnia. Seeking professional medical advice before starting any new supplement regimen is always recommended, especially for individuals with underlying health conditions or those taking medications.

The Final Verdict on L-Theanine and Caffeine

The relationship between L-Theanine and caffeine is a fascinating one, with both substances having their unique strengths and weaknesses. The research suggests that when combined, they can create a powerful duo for stress reduction and cognitive enhancement.

L-Theanine, an amino acid found in green tea and coffee, has calming effects that can reduce physiological stress responses and counteract some of the less desirable physiological effects of caffeine, such as increased blood pressure and disrupted sleep. On the other hand, caffeine, a potent central nervous system stimulant, can enhance the beneficial effects of L-Theanine on cognitive function, such as attention and focus. The combination of L-Theanine and caffeine improves cognitive performance and increases subjective alertness.

Despite the promising results, it's crucial to remember that the Food and Drug Administration (FDA) does not regulate supplements, including those containing L-Theanine. Therefore, consumers must exercise caution when choosing such products. It's essential to find the right dosage and consult with a healthcare professional, especially if you have underlying health conditions or are taking medication. 

NMN Bio offers NAD+ Brain, formulated with 100 mg of L-Theanine and combined with 50 mg caffeine per serving, fosters a harmonious synergy that promotes calm focus without the jitters, making it an appealing option for individuals seeking heightened cognitive performance.

Researched and reviewed by Dr Elena Seranova, Ph.D.

Dr Seranova holds a master's degree in Translational Neuroscience from the University of Sheffield, UK, and a Ph.D in Stem Cell Biology and Autophagy from the University of Birmingham, UK. She is a published author in multiple peer-reviewed journals, including Cell Reports and Developmental Cell.


Baba et al. Theanine maintains sleep quality in healthy young women by suppressing the increase in caffeine-induced wakefulness after sleep onset. Food & Function. (2023)

Camfield et al. Acute effects of tea constituents L-Theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutrition Reviews. (2014)

Giesbrecht et al. The combination of L-Theanine and caffeine improves cognitive performance and increases subjective alertness. Nutritional Neuroscience. (2010)

Hidese et al. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. (2019) 

Kahathuduwa et al. Effects of L-Theanine–caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT. Scientific Reports. (2020)

Owen et al. The combined effects of L-Theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience. (2008)

Ritsner et al. L-Theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. Journal of Clinical Psychiatry. (2011) 

Rogers et al. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology. (2008) 

Sohail et al. The Cognitive-Enhancing Outcomes of Caffeine and L-Theanine: A Systematic Review. Cureus. (2021) 

Yoto et al. Effects of L-Theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. Journal of Physiological Anthropology. (2012)