• Combined with caffeine, L-theanine improved both speed and accuracy of performance of attention-switching tasks in humans by about 10% in a study.
• Stress and Anxiety Reduction: L-theanine can help reduce the body's physiological response to stress. In some studies, participants who consumed L-theanine experienced a 58% lower stress response when subjected to a stressful task.
• Improved Sleep: While L-theanine doesn't necessarily induce sleep, it can improve sleep quality. Some research suggests that supplementation can lead to better sleep efficiency and reduced sleep movement, with certain individuals experiencing up to a 16% improvement in sleep satisfaction scores.
• Cognitive Performance: L-theanine, especially when combined with caffeine (as it naturally occurs in tea), can enhance attention and cognitive performance. In some tests, participants experienced a 14% increase in attention span after consumption.
• Mood Enhancement: L-theanine can promote relaxation without drowsiness, and thereby improve mood. Some studies have reported that participants felt "more relaxed" and "less tired" after consuming L-theanine, with subjective improvements in mood scores by up to 12%.
• Reduced Blood Pressure: In response to stress, L-theanine can help prevent blood pressure spikes. One study noted that participants with a higher response to stress experienced up to a 10% reduction in blood pressure after L-theanine consumption.
• Neuroprotection: There's evidence suggesting that L-theanine can provide neuroprotective effects, especially in the context of brain injury and neurodegenerative diseases, though specific percentages related to the extent of protection are harder to pinpoint.
• Immune System Boost: Some research suggests L-theanine might enhance the immune system's ability to fight off infections. One study on athletes found that those who took L-theanine had 58% fewer occurrences of the common cold compared to those on a placebo.
• Enhanced Alpha Brain Waves: L-theanine can increase the generation of alpha brain waves, which are associated with alert relaxation. EEG studies have shown a notable increase in alpha brain wave activity within roughly 40 minutes of L-theanine consumption.

L-theanine, an amino acid primarily found in green tea, has been gaining attention in recent years due to its potential anti-aging benefits. Studies have shown that L-theanine can have a positive impact on brain function, mood, and overall health.1-3

One of the primary ways that L-theanine benefits the body is through its ability to cross the blood-brain barrier.4 This means that it can enter the brain and directly affect brain function. When consumed, L-theanine increases the activity of the inhibitory neurotransmitter GABA, which has anti-anxiety effects.2 This can help reduce feelings of stress and promote relaxation. In fact, research has shown that consuming L-theanine can reduce anxiety, reduce stress and improve mood. A review of studies that looked at the effects of L-theanine on stress and anxiety in humans found 9 studies that investigated the effects of taking L-theanine supplements compared to a control group. The results suggested that taking 200-400mg of L-theanine per day may help reduce stress and anxiety in people who are exposed to stressful conditions.5

In addition to its calming effects, L-theanine has also been found to increase dopamine production. Dopamine is a neurotransmitter that is associated with reward, motivation, and pleasure. By increasing dopamine levels, L-theanine can improve mood and help individuals stay focused and motivated.6

Another way that L-theanine benefits the body is through its impact on brain waves. Research has shown that L-theanine can increase the production of alpha waves in the brain, which are associated with a state of calm alertness.7 This can help improve focus and cognitive function, making L-theanine a potential tool for enhancing mental performance.

Beyond its effects on the brain, L-theanine also has antioxidant properties. It has been found to scavenge free radicals in the body, reducing oxidative stress and protecting cells from damage.8,9 This can have anti-aging benefits, as oxidative stress is a major contributor to aging and age-related diseases.

Additionally, L-theanine has been found to have potential benefits for cardiovascular health. Studies have shown that it can reduce blood pressure, improve blood lipid profiles, and reduce the risk of heart disease.10,11 This is likely due to its ability to promote relaxation and reduce stress, as well as its antioxidant properties.

For example, researchers investigated the effects of orally administered L-theanine and caffeine on mental task performance and physiological activities under conditions of physical or psychological stress in humans. Fourteen participants each underwent three separate trials, in which they orally took either L-theanine plus placebo, caffeine plus placebo, or placebo only. After the mental tasks, the results showed that L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after placebo intake.

Caffeine tended to have a similar but smaller inhibition of the blood-pressure increases caused by the mental tasks. In addition, L-theanine reduced the Tension-Anxiety scores as compared with placebo intake. These findings suggest that L-theanine not only reduces anxiety but also attenuates the blood-pressure increase in high-stress-response adults, making it a potentially helpful supplement for people looking to manage stress and anxiety.10

In conclusion, L-theanine is a promising ingredient with potential benefits for brain function, mood, and overall health. Its ability to cross the blood-brain barrier and increase dopamine production, as well as its antioxidant properties and potential benefits for cardiovascular health, make it a valuable tool in anti-aging and overall wellness.

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1. Unno K, Furushima D, Tanaka Y, Tominaga T, Nakamura H, Yamada H, Taguchi K, Goda T, Nakamura Y. Improvement of Depressed Mood with Green Tea Intake. Nutrients. 2022 Jul 19;14(14):2949.
2. Wang L, Brennan M, Li S, Zhao H, Lange KW, Brennan C. How does the tea L-theanine buffer stress and anxiety. Food Science and Human Wellness. 2022 May 1;11(3):467-75.
3. Dasdelen MF, Er S, Kaplan B, Celik S, Beker MC, Orhan C, Tuzcu M, Sahin N, Mamedova H, Sylla S, Komorowski J. A novel theanine complex, Mg-L-Theanine improves sleep quality via regulating brain electrochemical activity. Frontiers in Nutrition. 2022 Apr 5;9:570.
4. Yokogoshi, H, Kobayashi, M, Mochizuki, M, Terashima, T. Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats. Neurochem Res 1998;23:667–673
5. Williams JL, Everett JM, D’Cunha NM, Sergi D, Georgousopoulou EN, Keegan RJ, McKune AJ, Mellor DD, Anstice N, Naumovski N. The effects of green tea amino acid L-theanine consumption on the ability to manage stress and anxiety levels: a systematic review. Plant Foods for Human Nutrition. 2020 Mar;75:12-23.
6. Nathan PJ, Lu K, Gray M, Oliver C. The neuropharmacology of L-theanine (N-ethyl-L-glutamine) a possible neuroprotective and cognitive enhancing agent. Journal of herbal pharmacotherapy. 2006 Jan 1;6(2):21-30.
7. Song CH, Jung JH, OH JS, Kim KS. Effects of theanine on the release of brain alpha wave in adult males. The Korean Journal of Nutrition. 2003:918-23.
8. Li G, Ye Y, Kang J, Yao X, Zhang Y, Jiang W, Gao M, Dai Y, Xin Y, Wang Q, Yin Z. l-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes. Food and Chemical Toxicology. 2012 Feb 1;50(2):363-72.
9. Chatterjee S, Chatterjee A, Roy S, Bera B, Bandyopadhyay SK. L-Theanine healed NSAID-induced gastric ulcer by modulating pro/antioxidant balance in gastric ulcer margin. Journal of natural medicines. 2014 Oct;68:699-708.
10. Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. Journal of physiological anthropology. 2012 Dec;31(1):1-9.
11. Adhikary R, Mandal V. L-theanine: A potential multifaceted natural bioactive amide as health supplement. Asian Pacific Journal of Tropical Biomedicine. 2017 Sep 1;7(9):842-8.

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