L-Theanine Benefits for Athletes: The Evidence Base
L-theanine appears more and more often in the composition of pre-workout complexes and «nootropics» for athletes. Manufacturers promise focus, calm before the start, and better sleep. Our editorial team checked what of this is actually confirmed by research and what still remains a hypothesis or marketing.
Why athletes are interested in theanine
Sport is not only about muscles and endurance, but also about the mental state: the ability to concentrate, to control nerves before the start, to recover quickly after exertion. It is precisely these aspects, rather than a direct increase in strength, that the interest in theanine is aimed at. No anabolic or ergogenic effect in the classic sense is expected from it.
The second reason for its popularity is caffeine. It is one of the few supplements with a strong evidence base for performance, but in some people it causes tremor, anxiety, a rapid heartbeat, and sleep problems. Theanine is viewed as a tool that can soften these effects without cancelling out the benefits of caffeine.
The third reason is sleep. Intense training, evening starts, flights, and competitive stress often disrupt sleep, which is critically important for recovery. A supplement that helps you relax without sedation looks like an attractive alternative to sleeping pills.
Finally, theanine is considered safe and is not on the WADA Prohibited List, so its use carries no anti-doping risk provided the product is not contaminated with prohibited substances. However, safety does not equal effectiveness, and the evidence base should be assessed separately for each claimed benefit.
- Cognitive area:attention, accuracy, switching between tasks.
- Psycho-emotional area:pre-start nervousness, stress response.
- Recovery:sleep quality after training and competition.
- Companion to caffeine:softening of tremor and «jitteriness».
Attention and cognitive function
Most research is devoted to the effect of theanine on attention, and mostly in combination with caffeine. In the work of Owen and colleagues (2008), a combination of 100 mg of theanine and 50 mg of caffeine improved accuracy in an attention-switching task and reduced sensitivity to distracting stimuli compared with placebo.
Giesbrecht and colleagues (2010) repeated a similar design with doses of 97 mg of theanine and 40 mg of caffeine and also obtained improvements in task-switching accuracy and subjective alertness. Haskell and colleagues (2008) showed that a combination of 250 mg of theanine and 150 mg of caffeine gave better results on a number of tests than either substance alone.
The meta-analysis by Camfield and colleagues (2014) summarized the acute effects of tea components: a combination of theanine and caffeine at doses up to 50 mg and 100 mg respectively improved attention in the first two hours after intake. At the same time, the authors noted the heterogeneity of the studies and the relatively small effect sizes.
For an athlete, these data are most relevant in disciplines where accuracy and control matter: shooting, combat sports, team sports, chess, e-sports. However, most of the work was carried out in laboratory cognitive tests rather than during real training or competition, so the direct transfer of the results is limited.
Stress, anxiety, and sleep
A study by Kimura and colleagues (2007) showed that 200 mg of theanine before a stressful task lowered heart rate and secretory immunoglobulin A — markers of the physiological stress response. Yoto and colleagues (2012) studied the effect of theanine on blood pressure during physical and psychological stress and recorded a smaller rise in pressure in individuals prone to high values.
A four-week randomized study by Hidese and colleagues (2019) showed improvements in self-rated stress, anxiety, and sleep quality with a daily intake of 200 mg. A systematic review by Williams and colleagues (2020) concluded that theanine may reduce stress and anxiety in people under stress, although the evidence is still insufficient for firm recommendations.
As for sleep, a review by Rao and colleagues (2015) summarized data that theanine may improve subjective sleep quality without causing daytime drowsiness. However, a significant portion of the work was funded by manufacturers and had small samples. There is practically no research specifically on athletes during periods of intense loads.
So, for an athlete with pre-start nervousness or disturbed sleep, theanine may be a reasonable low-risk attempt, but one should not expect it to replace sleep hygiene, psychological preparation, or adjustment of the training load.
Physical performance: what is known
There is no direct evidence that theanine increases strength, power, or endurance. There are few studies with such a design, and they do not show a consistent ergogenic effect. The IOC consensus statement on dietary supplements (Maughan et al., 2018) does not include theanine in the list of agents with a proven effect on performance.
Some of the work examined pre-workout mixtures in which theanine was one of many components alongside caffeine, beta-alanine, creatine, and other substances. Such a design does not allow the contribution of theanine to be isolated, and any positive results are more logically explained by caffeine.
| Claimed benefit | Level of evidence | Editorial comment |
|---|---|---|
| Attention (paired with caffeine) | Moderate | Several RCTs and a meta-analysis, effects small |
| Reduction of the stress response | Moderate / low | Small samples, laboratory conditions |
| Sleep quality | Low | Mostly subjective ratings |
| Strength, endurance | None | No direct evidence of an effect |
| Softening of caffeine's side effects | Low / moderate | Data conflicting, dose-dependent |
An interesting but under-researched area is the possible effect of theanine on the immune response after intense exertion. There are isolated studies on a combination of theanine and cystine, but they are insufficient for any practical conclusions.
Therefore, the editorial team recommends viewing theanine as an auxiliary means for the psycho-emotional state, rather than as a supplement for directly boosting athletic performance.
Limitations of the evidence base
The first limitation is the size of the studies. Most of the work included from a few dozen to a hundred participants, and the observation period rarely exceeded a few weeks. With such samples it is easy to obtain random positive results or to miss real but weak effects.
The second limitation is the population. The participants were mostly students and healthy adults, not athletes under a training load. The stress response in a trained person and their sensitivity to caffeine may differ.
The third limitation is conflict of interest. A significant portion of theanine research was funded by companies that manufacture patented forms of the raw material, or by tea producers. This does not make the results false, but it calls for caution and independent replication.
The fourth is the variety of doses and tests. The studies used doses from 50 to 400 mg and dozens of different cognitive tests, which complicates comparison and meta-analysis.
Editorial conclusions
The evidence base for L-theanine in athletes is strongest in the area of attention and cognitive productivity, when it is combined with caffeine. On its own, theanine may somewhat reduce the physiological stress response and, possibly, improve subjective sleep quality.
There is no evidence of a direct increase in strength, power, or endurance, so one should not expect an «ergogenic» effect from theanine.
It is a low-risk supplement that can reasonably be tried to manage pre-start nervousness or to soften the side effects of caffeine, while assessing your own response.
To form a complete picture, we recommend reading our articles on the mechanism of action of L-theanine, on dosing and timing, and on combining theanine with other supplements.
References
- Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008;11(4):193–198.
- Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010;13(6):283–290.
- Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol. 2008;77(2):113–122.
- Camfield DA, Stough C, Farrimond J, Scholey AB. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev. 2014;72(8):507–522.
- Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007;74(1):39–45.
- Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362.
- Williams JL, Everett JM, D'Cunha NM, et al. The effects of green tea amino acid L-theanine consumption on the ability to manage stress and anxiety levels: a systematic review. Plant Foods Hum Nutr. 2020;75(1):12–23.
- Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
