The Combination of Caffeine and L-Theanine
L-theanine and caffeine is a novel nootropic stack that is growing increasingly popular within communities looking to improve mental and physical performance. They are combined for their synergistic effects on cognitive function and energy. L-theanine, an amino acid found in tea leaves, promotes relaxation and reduces stress by modulating neurotransmitter activity, while caffeine, a well known stimulant, increases alertness and energy levels by blocking adenosine receptors in the brain. When taken together, these compounds can balance each other out, mitigating the jittery effects of caffeine while aiding its positive impacts on focus and mental clarity.
Research has shown that this combination can improve attention, reaction time, and cognitive performance more effectively than either substance alone. Einöther & Martens, 2013 reported that 100 mg of caffeine paired with 200 mg of L-theanine improved both speed and accuracy in cognitive tasks. This synergy makes the combination particularly beneficial for tasks requiring sustained attention and mental endurance, especially during intense workouts, particularly those that involve changing stimuli such as CrossFit and Hyrox. Whilst you're here, be sure to take a look at our Energy Hydration Sachets, which contain a 1:2 ratio of caffeine (100mg) and l-theanine (200mg). If you would like to sample our full range of electrolyte sachets, be sure to explore our variety pack of hydration sticks.
Caffeine and L-Theanine for Cognitive Function
As discussed, L-theanine and caffeine work synergistically, a mechanism which can improve cognitive function through several, complex neurophysiological mechanisms. L-theanine reduces fMRI BOLD expression, decreasing brain activity during mind wandering and increasing vigilance to detect distractor stimuli, while also lowering the responsiveness of regions processing visual stimuli to distractors (Kahathudawa et al., 2018). This may help maintain focused attention and whilst also reducing susceptibility to distractions. Additionally, L-theanine modulates EEG alpha oscillations, decreasing background alpha oscillations associated with relaxation and increasing attention-related alpha oscillations, thus promoting a state of alert relaxation conducive to better cognitive performance (Gomez-Ramirez et al., 2008).
L-theanine also influences neurotransmitter systems by increasing dopamine levels and decreasing the release of serotonin, noradrenaline, and GABA (Kimura et al., 1971). This modulation may contribute to better mood and alertness without overstimulation. Furthermore, L-theanine acts as a glutamate inhibitor, preventing excessive excitatory activity in the brain and promoting a balanced neural environment (Kakuda et al., 2002).
Caffeine, on the other hand, increases the levels of several neurotransmitters, including dopamine, serotonin, glutamate, and noradrenaline (Solinas et al., 2002). This leads to heightened arousal, improved mood, and better cognitive processing. The combination of L-theanine and caffeine leverages these complementary effects, with L-theanine providing a calming influence which counteracts the jitteriness of caffeine, resulting in improved attention, faster reaction times, and better overall cognitive performance.
Caffeine & L-Theanine Research Review
The growing body of evidence to support caffeine supplementation alongside theanine has been summarised in Table 1 below, but will also be discussed at length in the following section.
A review of 11 randomised, placebo controlled studies by Camfield et al., 2014 explored the synergistic impact of L-theanine and caffeine on cognitive function and mood. The outcome measures of mood were alertness, calmness, and contentedness, derived from the Bond-Lader scales, and state anxiety, from the State-Trait Anxiety Inventory. Cognitive measures assessed were attentional switch, intersensory attention, and rapid visual information processing. The research found that measures such as attention switching accuracy, unisensory visual attention, unisensory auditory attention all improved following caffeine and L-theanine supplementation.
Research by Owen et al. (2010) looked at supplementation of 50mg of caffeine, with and without 100mg of L-theanine, looking for the effects on cognition and mood. The researchers compared the effects of these subjects with placebo in 27 participants, looking at the effects on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood. The results found that caffeine and L-theanine had the greatest effect, improving measures across the board such as subjective alertness, speed and accuracy on an attention switching task, as well as reduced susceptibility to distracting information in a memory task.
Haskell et al. (2008) carried out a randomised, placebo-controlled, double blind, balanced crossover study which investigated the acute cognitive and mood effects of L-theanine (250mg), caffeine (150mg) as well as their combination. The study measured salivary caffeine levels, headache ratings, reaction time and sentence verification accuracy, amongst other cognitive measures. They found that caffeine on its own led to a faster reaction time, visual processing accuracy and improved self-reported mental fatigue. The combination of L-theanine and caffeine improved these same measures, and more, including reduced headache & tiredness rating, and increased alertness ratings.
Research in the same year from Rogers et al. (2008) also looked at the effects of caffeine and L-theanine supplementation at doses of 250mg of caffeine (a high dose) and 200mg of theanine. They discovered that theanine antagonised the effect of caffeine on increasing blood pressure, however no other significant effects were found.
Research led by Dodd et al. (2015), a double blind, placebo controlled study, looked at the effects of caffeine and L-theanine on cerebral blood flow, cognition and mood. The results showed that caffeine reduced oxygenated haemoglobin and increased deoxygenated haemoglobin, thus improving attention and mood. Meanwhile the combination of caffeine and L-theanine eliminated the vasoconstrictive and behavioural effects of just caffeine.
Foxe et al. (2012) studied 27 participants performing the Sustained Attention to Response Task over two hour sessions. The effects of caffeine (50mg) and L-theanine (100mg) supplementation both on their own and in combination was examined. The results showed that both caffeine and L-theanine and L-Theanine significantly reduced error rates compared to placebo, but their combination didn’t necessarily provide additional benefits in this particular study.
Suzanne J. L. Einöther et al. (2010) investigated the effects of L-theanine (97mg) and caffeine (40mg) in combination against placebo, looking at the effects on attention tasks and self reported alertness. The study found that the combination significantly improved task switching performance, but not subjective alertness.
Kelly et al. (2008) examined the cognitive effects of combining 100 mg of L-theanine and 50 mg of caffeine. Their participants underwent tasks involving cued shifts of attention whilst their brain activity was recorded. The combination of L-theanine and caffeine increased hit rate and target discriminability compared to placebo, whilst caffeine alone improved discriminability, but not hit rate. L-theanine on its own had no effect.
Interestingly, research by Chanaka N. Kahathuduwa et al. (2020) investigated the impact of L-theanine and caffeine on cognitive function in children with ADHD. In this randomised controlled trial, participants received a combination of L-theanine and caffeine. The combination of the two compounds together improved cognition composite scores and performance in tasks, indicating better attention and impulse control, whilst also reducing task-related reactivity in the brain.
Table 1: Studies examine the effect of caffeine and L-theanine on cognition.
|
References |
Participants |
Intervention |
Timing |
Key findings |
|
Zaragoza et al., 2019 |
20 M Collegiate athletes, age = 20.5 ± 0.4 |
CAF (1 mg/kg) + Theanine + Tyrosine vs PLA |
30 min |
|
|
Kahathudawa et al., 2017 |
20 M healthy, age = 21-23 |
L-theanine (200 mg) vs CAF (160 mg) vs Theanine + CAF vs Black tea vs PLA |
30 min |
|
|
Owen et al., 2008 |
13 M, 14 F, age = 28.3 ± 5.4 |
CAF (50 mg) vs Theanine (100 mg) vs CAF + Theanine vs PLA |
60-90 min |
attention-switching task at 90 min. |
|
Giesbercht et al., 2010 |
16 M, 28 F, age = 21.3 ± 3.2 |
CAF (40 mg) + Theanine (97 mg) vs PLA |
20-70 min |
alertness, ↓ task induced fatigue |
|
Haskell et al., 2008 |
9 M, 15 F, age = 21.3 ± 0.8 |
CAF (150 mg) vs Theanine (250 mg) vs CAF + Theanine vs PLA |
30-90 min |
alertness, ↓ tiredness, ↓ mental fatigue, ↓ headache |
|
Rogers et al., 2008 |
48 M, age = 20.5 ± 2 |
CAF (250 mg) vs Theanine (200 mg) vs CAF + Theanine vs PLA |
30 min |
|
|
Dodd et al., 2015 |
10 M, 14 F, age = 21.8 ± 3.2 |
CAF (75 mg) vs Theanine (50 mg) vs CAF + Theanine vs PLA |
30 min |
|
|
Foxe et al., 2012 |
27 M, age = 26 |
CAF (50 mg) vs Theanine (100 mg) vs CAF + Theanine vs PLA |
|
|
|
Einother et al., 2010 |
11 M, 18 F, age = 30.6 ± 8.9 |
Theanine (97 mg) + CAF (40 mg) vs PLA |
10-60 min |
|
|
Kelly et al., 2008 |
5 F, 11 M, age = 27.5 |
Theanine (100 mg) vs CAF (50 mg) vs CAF + Theanine vs PLA |
30 min |
|
|
Kahathuduwa et al., 2018 |
9 M, age = 28.1 ± 9.4 |
Theanine (200 mg) vs CAF (160 mg) vs CAF + Theanine vs PLA |
60 min |
22.5 ms |
Caffeine & L-Theanine Dosage Ratios
Current research on the optimal dosage and timing of caffeine and L-theanine supplementation suggests that a 2:1 ratio of L-theanine to caffeine is effective in optimising cognitive function and increasing energy. Owen et al. (2010) demonstrated that this 2:1 ratio improved cognitive measures across the board such as subjective alertness, speed and accuracy on an attention switching task, as well as reduced susceptibility to distracting information in a memory task.
Another study by Foxe et al. (2012) looked at the same ratio and found cognitive benefits to both caffeine and L-theanine. Research by Einöther et al., (2010) looked into the effects of taking 97mg of L-Theanine and 40mg of caffeine (approx 2:1 ratio) compared to placebo. The combination of L-theanine and caffeine significantly improved attention on an attention switching task as compared to the placebo.
Supplementing Caffeine & L-Theanine
Current research suggests that combining caffeine with L-theanine may mitigate the sleep impairments often associated with caffeine supplementation alone. Caffeine is known to improve alertness and cognitive performance, but its stimulating effects can also interfere with sleep quality and increase sleep latency. However, L-theanine, an amino acid found in tea, has calming properties that can counterbalance caffeine's stimulatory effects.
Research has found that a combination of 250mg of L-theanine and 150mg of caffeine improved cognitive performance, and the study’s reviews of more literature suggests that the combination is indicative of relaxation without drowsiness, leading to decreased negative impact on sleep typically observed with caffeine alone (Haskell et al., 2008). Another study reported similar benefits, with L-theanine supplementation improving sleep efficiency and reducing sleep disturbances (Hidese et al., 2019). These findings suggest that L-theanine can offset caffeine's adverse effects on sleep, allowing for the cognitive benefits of caffeine without compromising sleep quality, making it a good option for those individuals who train later in the day, requiring the performance enhancing benefits of caffeine.
With regards to timing, the existing research suggests that taking caffeine combined with L-theanine in the morning is likely to improve focus and reduce stress. This timing leverages the wakefulness-promoting effects of caffeine whilst L-theanine may mitigate potential anxiety and jitteriness, setting a calm yet alert tone for the day. Alternatively consuming 30-60 minutes prior a cognitively or physically demanding task, or workout can benefit. This is because caffeine reaches peak plasma levels within 30 minutes, and L-theanine's calming effects can smooth out caffeine's stimulating effects, resulting in improved attention and reduced mind-wandering (Sohail et al., 2021).
Research suggests that there are upper limits to the safe daily intake of caffeine and L-theanine. For caffeine, the FDA advises a maximum daily intake of 400 mg for most adults, equivalent to about four to five cups of coffee. Consuming more than this can lead to adverse effects such as insomnia, jitteriness, and increased heart rate (FDA, 2021). Studies indicate that doses above 400 mg of caffeine daily may exacerbate anxiety and disrupt sleep patterns (Nawrot et al., 2003).
For L-theanine, studies have shown that doses up to 1,200 mg per day are generally well-tolerated without significant adverse effects. According to a review, the FDA has granted L-theanine GRAS (Generally Recognized As Safe) status at doses up to 250 mg per serving, with no known toxicity at higher levels used in studies (Borzelleca et al., 2006). However, beneficial effects on cognitive function and relaxation are typically observed with doses between 200-400 mg.
As always, we recognise that we are all genetically different and metabolise caffeine differently, so we recommend that you assess tolerance with 100mg of caffeine first and monitor effects. If you want information on how much caffeine or L-theanine you should take, we recommend that you speak to a medical professional.
Conclusion
In conclusion, the synergistic effects of caffeine and L-theanine offer both the cognitive and stimulatory physical benefits of caffeine and the calming effects of L-theanine for improved attention, reaction time and overall cognitive performance without the jitteriness often associated with caffeine alone. This combination may be particularly useful for tasks which require sustained focus and mental endurance in an athletic setting.
Frequently Asked Questions (FAQs)
What are the main benefits of combining caffeine and L-theanine?
Combining caffeine and L-theanine may improve cognitive function and energy levels more effectively than either compound alone. The combination has been shown in studies to improve attention, reaction time and overall mental clarity, with L-theanine potentially mitigating the jitteriness normally associated with caffeine.
How does L-theanine help counteract the negative effects of caffeine?
L-theanine is an amino acid found in tea leaves. It promotes relaxation and may reduce stress by modulating neurotransmitter activity. When taken with caffeine, it may help balance caffeine’s stimulatory effects, promoting a state of calm and alertness.
What is the optimal dosage ratio of L-theanine to caffeine for cognitive benefits?
The bodies of research which find beneficial properties of the combination generally incorporate a 2:1 ratio of L-theanine to caffeine, with positive effects including improvements in attention and accuracy in cognitive tasks.
Can combining caffeine and L-theanine improve sleep quality?
Combining a low dose of caffeine with L-theanine may mitigate the sleep impairment effects often associated with caffeine alone. L-theanine’s calming properties may counterbalance caffeine’s stimulatory effects, allowing those who incorporate the combination to benefit from the cognitive enhancements without compromising on sleep quality.
When is the best time to take caffeine and L-theanine?
Taking caffeine and L-theanine in the morning may improve focus and reduce stress throughout the day. Furthermore, consuming both 30-60 minutes before a cognitively demanding task or workout can improve performance by leveraging the positive effects of both.
References
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Kahathuduwa, C. N., Dhanasekara, C. S., Chin, S. H., Davis, T., Weerasinghe, V. S., Dassanayake, T. L., & Binks, M. (2018). l-Theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging study. Nutrition research (New York, N.Y.), 49, 67–78. https://doi.org/10.1016/j.nutres.2017.11.002
Gomez-Ramirez, M., Kelly, S.P., Montesi, J.L. et al. The Effects of L-theanine on Alpha-Band Oscillatory Brain Activity During a Visuo-Spatial Attention Task. Brain Topogr 22, 44–51 (2009). https://doi.org/10.1007/s10548-008-0068-z
Kimura, R., & Murata, T. (1971). Influence of alkylamides of glutamic acid and related compounds on the central nervous system. I. Central depressant effect of theanine. Chemical & pharmaceutical bulletin, 19(6), 1257–1261. https://doi.org/10.1248/cpb.19.1257
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Solinas, M., Ferré, S., You, Z. B., Karcz-Kubicha, M., Popoli, P., & Goldberg, S. R. (2002). Caffeine induces dopamine and glutamate release in the shell of the nucleus accumbens. The Journal of neuroscience : the official journal of the Society for Neuroscience, 22(15), 6321–6324. https://doi.org/10.1523/JNEUROSCI.22-15-06321.2002
Camfield, D. A., Stough, C., Farrimond, J., & Scholey, A. B. (2014). Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutrition reviews, 72(8), 507–522. https://doi.org/10.1111/nure.12120
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Dodd, F. L., Kennedy, D. O., Riby, L. M., & Haskell-Ramsay, C. F. (2015). A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. Psychopharmacology, 232(14), 2563–2576. https://doi.org/10.1007/s00213-015-3895-0
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