Stress and the overwhelm that comes with it are among the most common complaints that people have today. L-theanine is a popular natural supplement that’s known to reduce stress and anxiety, and help get you back to feeling like yourself again. 

L-theanine is found naturally in tea, and is also widely used in popular over-the-counter supplements, either alone or in combination with other relaxation-promoting nutrients and compounds.

In this article, we’ll discuss what l-theanine is, how it works in your body, the health benefits, and answer common questions related to this calming nutrient.

What Is L-Theanine?

L-theanine is an amino acid that’s found naturally in green and black tea and some types of mushrooms. It is best known for its ability to reduce stress and anxiety. 

Studies suggest that l-theanine may work by increasing neurotransmitters such as serotonin, GABA, and dopamine and providing neuroprotective effects which may enhance cognition. [1]https://pubmed.ncbi.nlm.nih.gov/16493792/[2]https://pubmed.ncbi.nlm.nih.gov/17182482/ 

Chemically, the theanine molecule resembles the amino acid and excitatory neurotransmitter glutamate and therefore may mimic or inhibit glutamate activity in your brain. At normal concentrations, glutamate plays a vital role in brain activities such as learning and memory by passing messages from one nerve cell to another. When glutamate is high, however, it can increase cellular activity and lead to over-excitement of neurons, potentially causing cell damage or even death.

The Benefits Of L-Theanine

People turn to l-theanine for a variety of reasons, including: 

  • Focus and concentration
  • Stress and feelings of anxiousness
  • Blood pressure management
  • Immune support

Focus and Concentration

Many people struggle with focus and attention and turn to caffeinated beverages to give themselves that extra push. Sure, a caffeine high may keep you attentive when you drink green or black tea, but you may be able to turn your brain power up a notch without giving yourself the jitters. 

Research shows that the natural combination of l-theanine and caffeine found in tea may help to improve focus and attention. 

In one study, researchers measured participants’ alertness, focus, and accuracy during demanding cognitive tasks after taking theanine and caffeine. The results showed that L-theanine and caffeine significantly improved accuracy during task switching, increased self-reported alertness, and reduced self-reported tiredness. [3]https://pubmed.ncbi.nlm.nih.gov/21040626/

Another study showed that l-theanine was especially helpful for increasing attention span in people who are prone to high anxiety. [4]https://www.sciencedirect.com/science/article/pii/S1756464611000351

One way in which l-theanine may promote attention is through a potential increase in alpha waves in your brain. Your brain produces five different types of “waves” or electrical oscillations related to different brain states. Research shows that l-theanine may help promote alpha waves, which promote a state of relaxed attention. [5]https://www.mdpi.com/2306-5710/2/2/13/htm Caffeine may counteract[6]https://pubmed.ncbi.nlm.nih.gov/8481621/ this effect, though. 

Stress and Feelings of Anxiousness 

The most well-known benefit of l-theanine is its ability to calm the mind and lower stress. 

In a double-blind, placebo-controlled study, researchers found that those taking l-theanine experienced reduced stress and improved overall mental health. The investigators suggest that these outcomes could be due to the structural similarities of theanine and the neurotransmitter glutamate.[7]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6836118/

Alpha waves may also play a role in the reduction of stress that many people experience with l-theanine. In addition to increasing focus, alpha waves produce a sense of calm and may also increase your ability to access creative centers in your brain.[8]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4741268/[9]https://www.mdpi.com/2306-5710/2/2/13/htm

Blood Pressure Management 

One of the primary physical markers of psychological stress is an increase in blood pressure. 

Research shows that through its stress-reduction activity, l-theanine may assist in blood pressure management by inhibiting some of the excitatory activity of glutamate in your brain.[10]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518171/

Of course, you can’t throw your doctor’s blood pressure management plan out the window and start taking l-theanine and expect good things. It’s worth bringing up with your doctor though, as it could help things along if you’re taking the right steps. 

Immune Support

L-theanine appears to have an impact on the immune system by altering the activity of several lines of immune cells[11]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518171/

In one study, 197 healthcare workers took a supplement containing theanine and catechins (phytonutrients found in tea) or a placebo for five months during flu season. At the end of the trial, the supplement group experienced significantly fewer flu-like symptoms compared to the placebo group, suggesting that the theanine-catechin combination may be effective for flu symptoms.[12]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049752/

Other studies show that l-theanine may be effective at decreasing inflammation by inhibiting the release of inflammatory proteins. In one trial, l-theanine helped to reduce inflammation in the airways of asthmatic participants. In yet another study, theanine acted as a protective measure against osteoarthritis.[13]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7400703/[14]https://pubmed.ncbi.nlm.nih.gov/27908701/


One of the most crucial prerequisites to a restful night’s sleep is a calm mind. Unfortunately, many people struggle to “turn off their brain” before bed and slip into a deep restorative sleep state. 

Due to its impact on brain waves and neurotransmitters related to sleep, l-theanine may promote a restful night sleep in those that have a hard time relaxing at night. 

In one study, researchers found that adolescents with ADHD, an attention disorder, taking 400mg of theanine a day showed improvements in sleep outcomes.[15]https://citeseerx.ist.psu.edu/viewdoc/download?doi=

Another animal study showed that l-theanine was able to partially reverse caffeine-induced sleep disturbances in rats. While the current research is promising, more in-depth human trials are still needed.[16]https://www.sciencedirect.com/science/article/abs/pii/S0091305712000123


Does l-theanine help with weight loss?

Animal research suggests that l-theanine, in combination with caffeine, may be responsible for green tea’s suppressive effect on body fat accumulation. However, there is currently a lack of controlled clinical trials to support the role of theanine in weight loss.[17]https://pubmed.ncbi.nlm.nih.gov/15011752/

The stress-lowering impact of theanine may also help improve mood, which could impact emotional eating, leading to weight gain.

Can you use melatonin and l-theanine together?

Melatonin and l-theanine are often found in sleep-promoting supplements. While melatonin is the primary hormone that your body produces to promote a feeling of sleepiness, theanine may enhance a sense of relaxation that allows you to wind down. 

There is currently no evidence to suggest they cannot be used simultaneously, but you should ask your doctor if there are any concerns about using both. 

Can you use l-theanine and GABA together?

Research suggests that l-theanine and GABA have a synergistic effect when used in combination and may improve sleep quality and duration. Interestingly, l-theanine appears to increase the expression of GABA and GABA receptors. 

There is currently no evidence to suggest they cannot be used simultaneously., but ask your doctor if there are any concerns about using them both. 

Can you take l-theanine with alcohol?

There is currently no known interaction between l-theanine and alcohol. In fact, animal studies show that l-theanine may have an antioxidant effect on liver tissue and may protect against alcohol-induced liver injury and fat accumulation. Clinical human trials are still needed.[18]https://pubmed.ncbi.nlm.nih.gov/22019691/

Of course, taking l-theanine with alcohol won’t shield your liver from all damage from heavy drinking, especially if your liver is already compromised. 

Does l-theanine help with ADHD?

Due to its impact on attention and focus, l-theanine may be a supportive supplement for people with ADHD. Research shows that adolescents with ADHD taking relatively high doses (400mg) of l-theanine have positive outcomes for improved sleep quality with no adverse side effects.

L-theanine may not replace medications, but could be a complement to your doctor’s treatment plan. 

How much l-theanine is in tea?

The amount of l-theanine in a cup of tea will vary depending on the type of tea and the amount of time the tea leaves have steeped. Black tea may contain up to 24 mg of theanine, while green tea contains around 8 mg per cup.

Can l-theanine help with anxiety?

The research around l-theanine and anxiety suggests that due to the relaxation-inducing effects of l-theanine, it may help calm your mind and combat feelings of stress. Furthermore, studies show that l-theanine may support overall mental health and wellness.

The mechanism by which l-theanine helps with anxiety may be due to its interaction with glutamate and glutamate receptors and its promotion of alpha brain waves. 

Who should not take l-theanine?

There are no known side effects associated with l-theanine; however, if you take stimulating medication, l-theanine may interfere with the stimulating effects as theanine has a calming impact on the nervous system. Taking l-theanine along with high blood pressure medications may also reduce blood pressure too much.

If you’re on medication, always ask your doctor or pharmacist about interactions. 

What’s the proper dosage of l-theanine?

There are no official guidelines regarding the dosage of l-theanine as it is a supplement and not a medication. The most common dosage of l-theanine is 100 to 200 mg, but some people may take as much as 900 mg per day. 

As there are no known side effects, you’re not likely to overdose on l-theanine if you follow package directions.