L-theanine is an amino acid found naturally in green tea. Tea has been a mainstay of the diet and has been sipped as a therapeutic beverage for thousands of years. It turns out that the connection between tea consumption and a calming, stress-reducing, and sleep-promoting sensation is more than anecdotal; it's science-backed [1].
Now, L-theanine can be found in larger quantities as supplements. Scientific studies have begun to uncover both the health benefits and the mechanisms behind L-theanine's calming effects. Let's dive into the researched benefits of taking L-theanine supplements.
What is L-Theanine?
L-theanine is an amino acid found in tea, notably green, black, and oolong teas. Unlike typical amino acids that serve as building blocks for proteins, L-theanine is primarily known for its relaxing properties [2].
While L-theanine is present in tea, supplements often provide it in higher concentrations as a standalone ingredient or in combination with other stress-relieving compounds [3].
L-theanine has well-researched benefits, including stress reduction, relaxation, cognitive enhancements, and even improved sleep quality.
Here, we'll dive into the health benefits of L-theanine supplementation and its potential to enhance human health and cognition.
L-Theanine Promotes Relaxation Through Altering Brain Waves
L-theanine promotes relaxing effects through its ability to influence brain waves. After taking L-theanine, it crosses the blood-brain barrier. Once in the brain, it promotes alpha-wave activity. Alpha waves are a brain wave pattern typically associated with a state of relaxation. This increase in alpha wave activity is thought to be the mechanism behind L-theanine's ability to make people feel more relaxed and less stressed [4, 5].
L-Theanine Boosts Mood
L-theanine can influence mood by modulating critical neurotransmitters in the brain. It increases GABA (gamma-aminobutyric acid) levels, serotonin, and dopamine [5].
GABA, the brain's primary inhibitory neurotransmitter, helps reduce neuronal excitability. This promotes a sense of calm and relaxation. L-theanine has been shown to both boost GABA levels and enhance GABA receptor function, amplifying its calming effects. [5]
L-theanine is also thought to increase serotonin and dopamine levels. These are known as "feel-good hormones," supporting a brighter mood, where serotonin is associated with well-being and happiness, and dopamine is linked to pleasure, reward, and focus [4].
By increasing GABA, serotonin, and dopamine, L-theanine can help promote a more positive mood.
Stress-Reducing Properties of L-Theanine
L-theanine can help defend against short-term stress and anxiety. Let’s say you’re about to give a presentation in front of hundreds of people. Your heart rate quickens and your palms become sweaty. These are symptoms of an acute stressor, the thought of public speaking.
Studies show that taking an L-theanine supplement during acute bouts of stress can help to bring you back to a baseline, less stressed state [6].
In fact, a study found that taking a 200mg L-theanine supplement twice daily helped to destress practicing pharmacy students [7].
L-Theanine Can Help To Lower Heart Rate
Heart rate increases during stress as part of the body's "fight or flight" response. When the brain senses a stressor, it triggers the release of stress hormones like adrenaline and cortisol, making the heart beat more rapidly.
This increased heart rate allows for quicker circulation of blood throughout the body, bringing more oxygen and nutrients to the body to fight off a stressor.
This is necessary for survival under a physical stressor, like being chased by a bear. But this process occurs in times of psychological or mental stress, too.
Studies show that taking L-theanine during a stressful situation reduces the heart rate response to the task [8].
L-Theanine Can Help To Decrease Blood Pressure
Blood pressure also rises under acute stress. Stress hormones constrict blood vessels, increasing resistance to blood flow.
Combined with a quickened heart rate, narrowed blood vessels increase blood pressure. Elevated blood pressure delivers oxygen and nutrients to prepare the body for action [9].
Over time, elevated blood pressure is associated with a host of chronic conditions, like heart disease, making it important to keep a normal blood pressure level [9].
A study found that taking an L-theanine supplement helped to curb the rise in blood pressure associated with a mentally stressful task [10].
L-Theanine Improves Brain Function
Research shows that L-theanine can significantly enhance aspects of brain function.
A four-week study found that participants taking a 200 mg L-theanine supplement daily showed improved executive function and verbal fluency. It was particularly beneficial for individuals with lower baseline cognitive scores. This study shows that L-theanine may boost cognitive performance [3].
Another study examining the combined effects of L-theanine (97 mg) and caffeine (40 mg) found notable improvements in accuracy during task-switching and self-reported alertness. Participants also reported reduced tiredness, showing that L-theanine enhanced cognition and defended against mental fatigue [11].
These findings demonstrate L-theanine's ability to act on brain function, including executive function, verbal fluency, and alertness.
Sleep Quality Improves When Taking L-Theanine
Getting quality sleep is a critical health habit that impacts nearly every facet of health. Numerous studies have shown that L-theanine relaxes and prepares the body for sleep. Calming down before bed can help to improve sleep quality across healthy adults, children with ADHD, and adults with major depressive disorder [5].
A study found that L-theanine supplementation reduced sleep latency, how long it takes to fall asleep, and sleep disturbance, waking throughout the night. The study also found that participants reduced their need for sleep medications while using L-theanine. This is a critical finding because while sleep medications can help to improve sleep, they are often accompanied by unwanted side effects like grogginess and dependency [3].
In fact, a review shows that taking 200 mg of L-theanine before bedtime could enhance sleep quality. Unlike other sleep aids, L-theanine promotes restful sleep without causing morning grogginess [12].
Another study looked at the impact of taking 400mg of L-theanine (Suntheanine®) before bed in a group of male children with ADHD. ADHD is often accompanied by having trouble getting quality sleep. The study showed that the boys who took L-theanine improved sleep efficiency, the ratio of time spent asleep to time spent in bed [13].
A study conducted in patients with major depressive disorder (MDD) found that taking L-theanine was associated with cognitive and sleep benefits. Most notably, taking L-theanine was associated with fewer sleep disturbances at night [14].
So, how does L-theanine promote sleep quality? In addition to its relaxation effect, L-theanine may also promote sleep through its impact on NMDA. Through mice studies, researchers hypothesize that the mechanism behind L-theanine’s sleep-promoting benefits may be related to its action as a partial agonist for the N-methyl-D-aspartate receptor [15].
These findings highlight L-theanine's benefits to sleep quality without the side effects of medications. For science-backed tips on getting good quality sleep, check out this article.
Is L-Theanine Safe to Take?
In the scientific studies referenced, L-theanine was taken in doses between 200-400 mg per day. L-theanine is generally recognized as a safe supplement to take, with no adverse events reported while under study. As with all supplements, it’s recommended that you consult with your healthcare provider before beginning supplementation. Women who are nursing or pregnant should not take L-theanine.
L-theanine has largely been studied in healthy populations. Further research is warranted to determine the impact of L-theanine in those with chronic conditions.
Key Takeaways
- L-theanine is an amino acid naturally found in tea, mainly green tea.
- It promotes relaxation by increasing alpha wave activity in the brain and boosting GABA, serotonin, and dopamine levels.
- L-theanine can reduce stress and anxiety, lower heart rate and blood pressure during stressful situations.
- L-theanine can also enhance cognitive function, including executive function, verbal fluency, and alertness.
- L-theanine improves sleep quality by reducing sleep latency and disturbances.
- Typical dosages in studies range from 200-400 mg per day, with no reported adverse effects in healthy adults.
References:
- https://www.mdpi.com/2306-5710/2/2/13
- https://www.sciencedirect.com/topics/medicine-and-dentistry/theanine
- https://www.mdpi.com/2072-6643/11/10/2362
- https://www.sciencedirect.com/topics/medicine-and-dentistry/theanine
- https://journalijbcrr.com/index.php/IJBCRR/article/view/855
- https://pubmed.ncbi.nlm.nih.gov/34562208/
- https://pubmed.ncbi.nlm.nih.gov/24051231/
- https://pubmed.ncbi.nlm.nih.gov/16930802/
- https://pubmed.ncbi.nlm.nih.gov/34994178/
- https://pubmed.ncbi.nlm.nih.gov/23107346/
- https://pubmed.ncbi.nlm.nih.gov/21040626/
- https://pubmed.ncbi.nlm.nih.gov/25759004/
- https://pubmed.ncbi.nlm.nih.gov/22214254/
- https://www.cambridge.org/core/journals/acta-neuropsychiatrica/article/effects-of-chronic-ltheanine-administration-in-patients-with-major-depressive-disorder-an-openlabel-study/0373674887BEA9598D911C7B274A3432
- https://link.springer.com/article/10.1007/s00213-011-2440-z