L-theanine is a naturally occurring amino acid found in tea leaves, particularly in green tea. It has been studied for its various effects on mental state, cognitive functions, and overall mood.

Key Effects and Benefits of L-theanine:

1. Stress and Anxiety Reduction:

   • L-theanine has been found to help reduce stress and anxiety[^1]. A systematic review suggested that an intake of 200-400 mg/day of L-theanine can assist in reducing stress and anxiety in people exposed to stressful conditions[^2].

2. Improvement of Mood and Cognitive Functions:

   • L-theanine administration has shown potential benefits on mood, sleep disturbances, and cognitive functions in patients with major depressive disorder[^3]. Additionally, it can improve attention and working memory, especially in middle-aged and older adults[^4].

3. Sleep Quality:

   • Regular intake of L-theanine can enhance sleep satisfaction and quality. Studies have noted improvements in sleep latency and reduced sleep disturbances[^5].

4. Neuroprotective Properties:

   • L-theanine has demonstrated antioxidant, anti-inflammatory, and neuroprotective effects. It may also help in regulating metabolic processes and protecting cardiovascular health[^6].

5. Promoting Relaxation:

   • L-theanine promotes relaxation without drowsiness by increasing alpha brain wave activity, which is associated with a relaxed, yet alert state[^7].

6. Adjunctive Therapy for Depression and Anxiety:

   • In adjunctive treatments for generalized anxiety disorder and depression, L-theanine has shown mixed results. For example, it did not significantly reduce anxiety in some trials but did improve self-reported sleep satisfaction[^8][^9].

Recommended Dosage:

• Research suggests that dosages between 200 and 900 mg per day are typically used in clinical studies. These doses have been effective in reducing anxiety and enhancing cognitive functions without significant side effects[^2][^4][^9].

^[1]: Anna C. Nobre, "L-theanine, a natural constituent in tea, and its effect on mental state," PubMed, 2008.
^[2]: Jackson L Williams, "The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review," PubMed, 2024.
^[3]: Shinsuke Hidese, "Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study," PubMed, 2016.
^[4]: Yoshitake Baba, "Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study," PMC, 2021.
^[5]: Shinsuke Hidese, "Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial," PMC, 2019.
^[6]: Ming-Yue Li, "L-Theanine: A Unique Functional Amino Acid in Tea (Camellia sinensis L.) With Multiple Health Benefits and Food Applications," PMC, 2022.
^[7]: Ai Yoto, "Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses," PMC, 2012.
^[8]: Jerome Sarris, "L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial," PubMed, 2018.
^[9]: Malkanthi Evans, "A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave®l-Theanine on Stress in a Healthy Adult Population," PMC, 2025.

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L-tyrosine is an amino acid that is crucial for producing several neurotransmitters, including dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). These neurotransmitters play significant roles in mood regulation, mental performance, and stress response.

Key Effects and Benefits of L-tyrosine:

1. Cognitive Function and Stress Response:

   • L-tyrosine helps replenish catecholamine levels in the brain, which can be depleted during stress. This replenishment helps maintain cognitive function and performance in stressful or cognitively demanding situations¹. Studies suggest that L-tyrosine can prevent the decline in cognitive function due to acute stress, though it does not enhance memory in non-stress conditions²³.

2. Improvement in Mood and Cognitive Functions:

   • Under stressful conditions, L-tyrosine has been found to alleviate reduced memory performance². This is particularly crucial in scenarios that require high cognitive demand and swift decision-making, such as military operations and multitasking environments.

3. Physical Performance and Fatigue:

   • L-tyrosine supplementation has been studied for its potential to improve endurance and reduce fatigue during prolonged physical activities. It is thought to help maintain attention and focus, which may indirectly support physical performance⁴.

4. Enhanced Neurotransmitter Synthesis:

   • By serving as a precursor to crucial neurotransmitters, L-tyrosine supports the production and maintenance of these chemicals in the brain. This role is especially significant during times of increased demand, such as stress, intense intellectual activity, and physical exertion¹.

Recommended Dosage and Safety:

• Clinical studies have utilized dosages ranging from 500 mg to 10,000 mg per day. Notably, one study reported no adverse effects with dosages of up to 150 mg per kilogram of body weight⁵. On average, effective doses for cognitive and stress-related benefits range between 500 mg and 2000 mg.

Conclusion:

L-tyrosine is a beneficial supplement for supporting mental performance, especially under stress. It helps replenish the brain’s supply of neurotransmitters, aiding in maintaining cognitive functions and improving mood during challenging situations.

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Footnotes

1. Examine.com, "What are L-tyrosine’s main benefits?" Examine, 2024. ↩ ↩²

2. Examine.com, "L-tyrosine supplement research," Examine, 2024. ↩ ↩²

3. Examine.com, "L-tyrosine's effects on memory under stress," Examine, 2024. ↩

4. Examine.com, "L-tyrosine and physical performance," Examine, 2024. ↩

5. Examine.com, "L-tyrosine dosage and safety," Examine, 2024. ↩