The Effects Of L-Theanine: An Amino Acid For Health
L-theanine—sometimes referred to as simply “theanine”—is a naturally occurring amino acid found in certain foods. Research and a long history of use across cultures suggest that this substance can have calming effects, which may be beneficial for those experiencing anxiety. Read on to learn more about L-theanine from supplements or green tea consumption and its potential health benefits.
Taking L-theanine with your doctor’s advice
Remember that while eating nutrient-dense foods may help reduce symptoms of certain mental health disorders, food and supplements are generally not recommended as replacements for professional mental health care. It’s also important to note that you should consult with your doctor and/or a qualified nutritionist about health and lifestyle modifications before making significant changes to your eating patterns or taking supplements.
L-theanine: An amino acid found in green tea
L-theanine is an amino acid that’s a natural constituent part of certain teas—such as green, black, and oolong—and some types of mushrooms. Supplements for L-theanine besides oolong, green, and black tea are also available in the form of powders, capsules, and liquids. This amino acid and its chemical constituents have been used by people of various cultures for centuries to reduce anxiety and promote relaxation, and it also increases subjective alertness in some cases. In addition, a recent prospective, double-blind, randomized trial suggests that it may improve attention, memory, other cognitive functions, and executive brain function due to its neuroprotective effects.
How L-theanine reduces stress
Although researchers aren’t sure exactly how L-theanine works in the body, it’s widely believed that it increases serotonin and levels of GABA—a neurotransmitter that plays a role in nervous system control—in the brain. It may also block L-glutamic acid from reaching glutamate receptors in the brain. The combined effect is the relaxation of the nervous system and a reduction in stress hormones like cortisol. Studies suggest that consuming 200 mg of L-theanine daily may significantly reduce stress levels and decrease high blood pressure associated with stress in eight weeks or less, with no known adverse side effects. However, individuals with high blood pressure should consult their mental health provider before taking any supplements or sedative medications.
The effects of L-theanine and the relationship between L-theanine and anxiety
Because L-theanine seems to help balance levels of various neurotransmitters related to stress, it may have positive effects on common symptoms of anxiety disorders and stress-related symptoms such as:
- Excessive worry and rumination
- Restlessness
- Irritability
- Muscle tension
Researchers have examined this relationship in an attempt to learn more about how natural substances like this may benefit those experiencing mental health disorders. One placebo-controlled clinical trial conducted in 2021 suggests that L-theanine may help reduce anxiety symptoms. It notes that the supplement “significantly increased frontal region alpha power compared to placebo in response to an acute stress challenge,” changes that are “indicative of relaxation in the brain and suggest a calming response.” The researchers in this placebo-controlled study also note that L-theanine consumption was “safe and well-tolerated by participants.”
The relationship between L-theanine and ADHD
Because of its effects on neurotransmitter levels, L-theanine may help reduce symptoms of other conditions as well, including attention-deficit/hyperactivity disorder (ADHD). This form of neurodivergence is estimated to affect 4.4% of adults and is characterized by difficulty focusing, impulsive behavior, and/or over-activity.
Cognitive benefits of L-theanine amino acid
Research may support the potential link between L-theanine and reduced ADHD symptoms. A 2021 review of studies on the topic, for example—which looked at both single-blind placebo-controlled and double-blind placebo-controlled trials—indicates that the combination of L-theanine and caffeine intake, in particular, may result in improvements in “short-term sustained attention and overall cognition,” with others suggesting that it could help with memory impairment as well.
Similarly, a 2019 clinical trial found that L-theanine, caffeine content, and/or the two in combination seem to improve sustained attention tasks and overall cognitive performance in children with ADHD by decreasing mind-wandering. Note, however, that L-theanine may lessen the effectiveness of certain stimulant medications often prescribed for ADHD, so ask your doctor before taking L-theanine as a supplement.
Better sleep quality and other potential benefits of amino acids like L-theanine
This substance found in green and black tea may also have other positive health effects. Because it’s thought to increase dopamine levels in the brain, it can help support positive moods—which is why it’s being explored as potentially beneficial for those experiencing major depressive disorder.
L-theanine promotes relaxation and better sleep quality
Taking l-theanine enables you to stay calm. It promotes a state of relaxation in the brain that makes it easier for people to improve their objective sleep quality—which has links to a variety of physical and mental health benefits. Plus, sleep disturbances are frequently associated with both depression and anxiety, so L-theanine may help mitigate symptoms in this way as well. Finally, some research points to the potential of L-theanine and other amino acids given via perioperative oral administration to reduce stress and aid in recovery after surgery.
Is L-theanine safe? Staying calm and regaining focus in life
L-theanine may help you regain focus and stay calm when you have anxiety. However, it’s recommended that you consult with a licensed healthcare provider before taking any kind of supplement or significantly altering your eating patterns. One reason is that some supplements can cause negative interactions with certain medications. A medical professional can also help you determine an appropriate dose if they decide that this supplement is safe for you to take. Consuming too much L-theanine can lead to headaches, nausea, and other side effects, it should be used with caution.
Always consult your doctor to avoid possible side effects of L-theanine
It’s also worth noting that while the safety and potential short-term benefits of L-theanine and other tea constituents have been well-documented, there’s a lack of research on the potential long-term side effects of consistently taking this supplement. It’s another reason why you should consult with your doctor before beginning any supplement use, especially if it’s over the long term.
Other treatments for anxiety
The potential effects of L-theanine do not make it a comprehensive treatment for clinical anxiety disorders or other mental health disorders. Like other lifestyle changes—such as eating nutritious foods and exercising regularly—it simply has the potential to help reduce symptoms as an adjunctive treatment and/or enhance the effects of professional treatment.
Cognitive behavioral therapy (CBT)
Treatment for anxiety typically consists of some form of psychotherapy, sometimes in combination with medication. Cognitive behavioral therapy (CBT) in particular is one of the most common forms of talk therapy for people with anxiety disorders. The aim of CBT is to help an individual learn to recognize and shift distorted thought patterns that may be contributing to distress and other symptoms. A therapist can also help a person learn healthy coping mechanisms that can assist them in managing symptoms as they arise.
Online therapy for stress and anxiety
For some people with anxiety, the thought of meeting with a healthcare provider in person may seem intimidating and could even cause a spike in symptoms. Research from randomized controlled trials suggests that online therapy can result in “sustained, clinically meaningful improvements” in anxiety symptoms just as in-person therapy can, so those who prefer this method may feel empowered to choose it.
Connect with an online therapist
If you’re interested in trying online therapy, you might consider a platform like BetterHelp. You can get matched with a licensed therapist who you can meet with via phone, video call, and/or in-app messaging to address the challenges you may be facing—and all from the comfort of home or anywhere you have an internet connection. Whatever method you may choose, effective, compassionate support for anxiety symptoms is available.
Takeaway
Read more below for answers to questions commonly asked about the effects of L-theanine.
What does taking L-theanine do for people with sleep problems and mental health issues?
Many who live with chronic physical and psychological stresses choose to take L-theanine, as details suggest that L-theanine enhances sleep quality, feelings of calmness, and one’s ability to stay grounded and mindful. It also boosts alpha waves, promoting both alertness and relaxation. Additionally, a 2010 randomized controlled trial supported the idea that the combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness in young adults. Several studies also suggest that L-theanine supports general disease prevention and can healthfully and safely lower one’s blood pressure.
L-theanine is a compound that occurs naturally in green tea (alongside green tea catechins) and is partially responsible for its light, springy flavor. Due to its ability to positively impact cognitive function, many scientists are considering researching the compound as a possible functional food additive. Some also regard L-theanine as a natural brain-derived neurotrophic factor.
Is it OK to take L-theanine amino acid daily to help with relaxation?
Additional research is needed to determine the full scope of benefits or considerations when it comes to taking L-theanine supplements daily. While the compound can be found naturally in green tea (alongside green tea catechins), too much of it can lead to headaches, poor sleep quality, and lethargy. Be mindful of proper consumption when drinking tea.
L-theanine supplements in small and controlled doses, however, can lead to lower blood pressure. Additionally, L-theanine can improve cognitive performance in a similar way that caffeine can, possibly offsetting symptoms that can be associated with generalized anxiety disorder while boosting cognitive function. Despite the potential health benefits of L-theanine and caffeine intake in improving sleep quality and other mental and physiological responses, it may be wise to consult a licensed professional before drinking tea or taking any supplement.
What are the side effects of L-theanine?
L-theanine is known to many as one of the naturally occurring amino acids that can be found in green tea. However, there are potential side effects that could be associated with the consumption of the compound.
Possible side effects of L-theanine primarily include lower blood pressure and increased cognitive function. If taken in excess, the person taking it may experience a headache or lethargy.
Beyond the role of L-theanine in supporting one’s blood pressure, L-theanine enhances recovery when it comes to symptoms associated with depression, brain injury, or anxiety disorder. For example, in clinical studies, L-theanine enhances the recovery process in patients who have experienced ischemic delayed neuronal death. To many, this would be a diagnosis that would otherwise pose a lengthy healing process, and possibly mild cognitive impairment in some.
Is L-theanine effective in helping people with ADHD regain focus and stay calm?
L-theanine can be helpful for those who experience ADHD and psychological or physiological stress. Many sources report anecdotally that people who live with the condition find it easier to focus if they consume caffeine (i.e., via green tea or coffee).
Researchers have since reviewed evidence associated with caffeine stimulation evaluated against L-theanine-related stimulation in people who live with the condition. L-theanine was clinically suggested to increase the presence of brain-derived neurotrophic factors in the body, which play an integral role in plasticity, learning, and memory. A 2002 study on the neuroprotective effects of green tea components theanine and catechins shows that theanine, when administered to animals, helps prevent brain cell damage. Both catechin and theanine may help protect brain cells. The study also notes that the neuroprotective mechanism is related not only to the glutamate receptor but also to the glutamate transporter. However, more research is needed to confirm these findings.
A 2019 crossover, double-blind, randomized placebo-controlled study on younger and older subjects showed that L-theanine administered at 200 mg/day has the potential for health promotion and is beneficial for individuals experiencing physical and psychological stresses.
This evidence suggests that L-theanine may benefit individuals who live with attention-deficit/hyperactivity disorder (ADHD). They may also experience additional secondary benefits associated with green tea or L-theanine as a compound, such as lower blood pressure and a sense of calm. In addition, a 2024 systematic review mentions that L-theanine helps control positive symptoms in patients with schizophrenia, anxiety, and schizoaffective disorder.
Is L-theanine for energy or better sleep quality?
L-theanine can be used for both energy and sleep. Those who live with underlying mental health conditions may respond positively to the relaxed feelings that L-theanine enhances; possibly feeling as if they’ve been given an energy boost. It can also work to calm the body, lower one’s blood pressure, and prepare them for restful sleep.
What time of day is best to take L-theanine?
Currently, there is no universally accepted “best time” to take L-theanine. Many take it as their schedule allows, whether that’s in the morning or before bed. Those taking it for its soothing, supportive properties may prefer to take it around bedtime to promote restful sleep and lower blood pressure.
It can be important to remember that L-theanine is one of the main amino acids naturally found in green tea. If you find yourself needing extra support, it can be helpful to know that you can likely find green tea around you, which may have lower concentrations of L-theanine. If you’re drinking tea, be aware of proper consumption guidelines.
While this isn’t the same as taking a supplement, it can be a way to reap some of the similar benefits. It is often beneficial to consult a licensed healthcare professional before taking any dietary supplement. It isn’t clear whether it's safe to take L-theanine for longer periods.
How long does it take for L-theanine to start working?
Many people report that it takes about an hour for L-theanine to work. It can be important to remember that people’s bodies are different, however, so this may not be true for all people. If you have questions about absorption or the supplement itself, you may benefit from speaking to your healthcare practitioner.
Does L-theanine help with anxiety and cognitive development?
L-theanine has been clinically suggested to reduce symptoms related to anxiety disorders of all types. Additionally, it also promotes calmness and focus, which can have a positive impact on your cognitive development. A 2008 study on the cognitive performance effects of L-theanine and caffeine found that combining the two can enhance one’s performance in cognitively demanding tasks. The combination of L-theanine and caffeine can improve one’s mood and mental state, which can be beneficial when performing a physical or mental task.
Can L-theanine cause weight gain?
Recent research suggests that L-theanine can have a suppressive effect on one’s body weight; instead helping them to maintain a healthy weight due to improved sleep and enhanced overall health.
Is L-theanine, an amino acid, hard on the liver?
In terms of tea constituents, L-theanine is not considered damaging to the liver. A 2018 study published in ScienceDirect shows that L-theanine, a functional food additive, helps prevent ETEC-induced liver damage.
L-theanine is generally recognized as safe for consumption due to its antioxidant properties, which demonstrate its role in disease prevention and health promotion. A 2023 study about L-theanine noted that theanine plays an immunoregulatory role in inflammation, the immune system, the intestinal tract, lymphocyte function, memory, nonmemory antibacterial cytokine responses, and the secretion of neurotransmitters.
A 2021 study on spontaneously hypertensive rats also found that taking L-theanine orally may contribute to the prevention of bladder dysfunctions. Additionally, some research suggests that L-theanine affects human cancer cells.
A 2009 study mentions that theanine significantly suppresses the growth of both lung cancer cells and leukemia cells. Meanwhile, a 2021 study found that L-theanine could suppress the invasion and development of prostate cancer cells. Despite this, more research is necessary to understand the potential clinical applications of L-theanine.
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