L-Theanine is an isomer (specifically an enantiomer, or non-superimposable mirror image) of the amino acids L-glutamate and L-glutamine; it was discovered centuries ago as one of the primary amino acids in green tea leaves. Some mushroom species and most tea leaves also contain small amounts of L-theanine.
Contrary to most of the amino acids that occur in nature, L-theanine is not used for protein synthesis in humans. Instead, it plays an important role as a cognitive aid (nootropic) by altering the activity of chemicals in the brain called neurotransmitters. And if you’re a coffee lover that craves the morning caffeine kick, an L-theanine supplement is the ideal pairing.
So, what are the health benefits of theanine? How does it work, exactly? Let's see what research has to say about this versatile nootropic.
L-theanine is highly bioavailable when taken orally, and it actively traverses the blood-brain barrier (1). Many studies have found that taking an L-theanine supplement can significantly enhance memory, alertness, mood, sleep, and resilience to stress (2).
The cognitive effects of L-theanine are appropriately described as "alert relaxation," which is to say it promotes a calming focus. This makes L-theanine (and green tea) great choices for stress/anxiety relief, studying, and productivity throughout the day. It can also help take the edge off of stimulants, notably caffeine.
In fact, research shows that combining L-theanine with caffeine creates a nootropic synergy that supports cognitive function and alertness more effectively than taking either nootropic on its own (3). Research also suggests that consuming L-theanine significantly increases alpha waves in the brain but has no effect on beta waves; the result of this is a better sense of relaxation without feeling sleepy or drowsy (4).
Alpha and beta waves are two predominant brainwaves that regulate our mood, attentiveness, and much more. When you are in a resting state or coming down from a set of busy activities, you are typically operating in the alpha brainwave space. Meditation is a prime example of an activity that induces alpha brainwaves. While theanine may not necessarily be a replacement for meditating, it works similarly on a physiological level.
When you are highly involved, active, or engaged in difficult mental activities, such as studying or taking an exam, your brainwaves are functioning at the beta level. Thus, taking L-theanine can help you feel calmer yet attentive.
L-theanine is an atypical amino acid in that it is not incorporated into body proteins. Instead, it acts independently on receptors throughout the central nervous system, thanks in part to being readily absorbed across the blood-brain barrier.
While other nootropics may help manage anxiety by increasing serotonin production, research suggests that L-theanine works through different mechanisms to reduce stress and improve mood. GABA (gamma-aminobutyric acid) and dopamine are ostensibly the primary neurotransmitters that theanine targets (5).
Paradoxically, large doses of L-theanine appear to reduce serotonin levels in the brain despite increasing L-tryptophan. In some regards, it’s beneficial that L-theanine doesn’t significantly increase serotonin levels as that can lead to drowsiness and disrupt your productivity during the day.
Another benefit of this is that L-theanine pairs well with supplements and prescription medication that fight anxiety by increasing serotonin (and other neurotransmitters) since they likely don't compete for the same receptors.
In fact, recent research suggests that combo therapy with antipsychotic medication and L-theanine may reduce anxiety symptoms more effectively than monotherapy in patients with chronic schizophrenia (6). Other research shows that even a modest 250 mg of L-theanine per day is safe and effective for reducing the symptoms of chronic depression, insomnia, and cognitive dysfunction (7).
Theanine is scanty in the human diet. The average cup of green tea (200 mL) only contains about 8 mg of L-theanine (8). Considering that a clinical dose of theanine is at a minimum of 100 mg, supplements are necessary.
Research thus far demonstrates that supplementing with roughly 100 - 400 mg of L-theanine per day can provide a variety of benefits, such as:
For daytime use, we recommend taking L-theanine and caffeine at the same time; this is the perfect combination for lasting energy and motivation without jitters or crashing. For sleep and nighttime use, cut out the caffeine.