The Neuroscience of L-Theanine and Sleep

So you’ve tried it all: herbal tea, over-the-counter drugs, avoiding caffeine, limiting alcohol, yet you are still wide-awake at 2 AM. Before you restart your Get Sleepy YouTube playlist, here’s something that needs your attention: you don’t need to trick your brain into sleeping, whether it’s using a sedative or elongated exposure to softer sounds. 

There is a natural amino acid named L-Theanine, found in tea leaves, that can relax your brain by increasing the levels of neurotransmitters like Gamma-aminobutyric acid (GABA). But what sets it apart is that it isn’t a sedative. 

 

What is L-Theanine and where does it come from?

Found in the leaves of the Camellia sinensis plant (the tea plant that produces green, black, white, and oolong tea), L-Theanine, unlike other amino acids, does not build protein. Instead, it affects neurotransmitters that create a calming effect. 

This water-soluble compound is also bioactive, offering numerous health benefits, including antioxidant, anti-inflammatory, neuroprotective, cardiovascular protective, and immune-regulatory properties. 

L-Theanine can be consumed naturally from drinking tea, but it can also be taken as a dietary supplement. Its concentration varies from tea to tea. 

How does L-Theanine impact brain function?

Before understanding how L-Theanine works, we need to take note of the primary neurotransmitters that it works through: 

• GABA: our brain’s primary inhibitory neurotransmitter—neurotransmitters are chemical messengers that carry messages from one nerve cell in your brain to another. There are two types of receptors that GABA binds to on neurons: GABA-A and GABA-B. While being different from one another, they ultimately make the nerve cells less responsive, lessening their ability to receive and send chemical signals that ultimately calm the brain down.  

• Dopamine: it is involved in multiple bodily functions, from movement to memory and mood. It also acts as a hormone, tied to our body’s ‘fight or flight’ syndrome.
  

• Serotonin: our “happy hormone” plays a crucial role in regulating mood, sleep, digestion, nausea, and sexual desire, among others.
  

• Glutamate: our brain’s primary excitatory neurotransmitter (stimulates a nerve cell, ensuring the chemical message gets passed on), plays a major role in learning and memory.
  

• Glycine: another inhibitory neurotransmitter similar to GABA, primarily acting on the spinal cord, brainstem, and retina. 

Now that we are clear on neurotransmitters, let’s see how they impact our brain. When one consumes a suitable amount of L-Theanine (100-400 mg/day), the compound:

• Increases the release of inhibitory neurotransmitters like GABA and glycine 

• Reduces the release of excitatory neurotransmitters like glutamate 

• May increase dopamine and serotonin release

To put it simply, it increases neurotransmitters that act as calming and pleasurable agents in the brain, and reduces the activity of its excitatory counterparts. Once L-Theanine permeates the blood-brain barrier (happening between 30-60 min, it also increases alpha brain waves, which are rhythmic brainwave patterns (8-13 Hz) most evident when a person is awake and in a relaxed state with their eyes closed. 

 

Does L-Theanine help you sleep better? 

Since L-Theanine calms our brain down and helps reduce anxiety, it is not surprising that it might be linked to better sleep. But first, let’s rewind a bit. What does good sleep even mean? 

Components of good sleep:

• At least 7-8 hours of quality sleep

• Good quality means going through the sleep cycles. The first sleep stages are called N1 (light sleep) and N2 (when the body starts to relax). 

• Deep sleep (Stage N3 or slow wave sleep): when brain waves slow down to their slowest frequencies. This is the deepest and most restorative sleep stage, where your body repairs itself. 

• Rapid Eye Movement (REM) sleep: the final stage of the sleep cycle, where the most vivid dreams happen. The brain becomes highly active, and the name comes from the fact that your eyes move rapidly under closed eyelids. 

Studies have shown that L-Theanine increases alpha waves, thereby encouraging the brain to be in a more relaxed state. This leads to an easier transition from wakefulness to deep sleep. Thus, it induces a prolonged period of slow-wave sleep, allowing for physical restoration and immune function strengthening. L-Theanine consumption has even been shown to reverse caffeine-induced wakefulness, suggesting that it may be a promising sleeping aid for the caffeine-induced insomniac populace. Studies in rats have also shown that L-Theanine can produce an anxiolytic effect (lower anxiety), and also decreases levels of the excitatory neurotransmitter glutamate. 

 

Risks associated with L-Theanine 

While the compound is considered to be safe, there are certain things to take into consideration:

• L-theanine is not approved as a drug by the Food and Drug Administration (FDA), but the FDA does consider the compound as “Generally Recognized As Safe (GRAS)” for use in foods and beverages (up to 250mg/serving). Although most consumers ingest L-Theanine naturally by drinking tea, it is also available as a nutritional supplement. 

• Chemotherapy patients should be cautious when taking L-Theanine, as some research shows that it may interact with some chemotherapy drugs. Check with your doctor.   

• Long-term L-theanine use is generally considered safe for most adults at recommended doses (up to 500mg/day), with few reported side effects, though mild issues like headaches, dizziness, or stomach upset can occur, especially at higher intake or from excessive tea consumption. More serious long-term risks are not well-documented, but caution is advised for those with low blood pressure (due to its blood pressure-lowering effect) or taking blood pressure meds, and its safety during pregnancy/breastfeeding isn't established.

• Even if L-Theanine appears to be generally safe, the caffeine in tea can spike your anxiety if consumed in large quantities. 

• As with many drugs and nutritional supplements, L-Theanine might interact with any other drugs, especially with drugs that regulate blood pressure. 

 

L-Theanine vs. CBD: friends or foes?

Although a CBD-terpene formulation has been shown to increase deep and REM sleep in participants with insomnia, data of the effects of L-Theanine on sleep architecture from human trials is lacking. However, given that  L-Theanine increases alpha brain waves and inhibitory neurotransmitters like GABA that may help to induce deep sleep, combining it with CBD may yield additional benefits on sleep because the two complement each other well in dealing with mental overstimulation and anxiety. 

 

To sum it all up

Here are some key takeaways: 

• L-Theanine is a natural amino acid found in tea leaves that can relax your brain without sedating it. 

• L-Theanine increases GABA release and alpha brain waves that slow down nerve cells and calm your mind. 

• A calmer and relaxed brain helps you transition from wakefulness to deep sleep, improving sleep quality.

• While generally safe, there are certain risks associated with L-Theanine mainly related to potential interactions with other drugs like blood pressure medications. 

• Combining L-theanine with CBD might provide additional benefits for sleep. 

• It is best to consult your health provider before starting any supplement, and make sure to only take supplements that have been tested for composition and contaminants by a 3rd-party independent analytical lab. 

FAQs

1. How does L-theanine affect the brain?

L-theanine influences brain chemistry by increasing alpha brain waves, which are linked to calm focus and relaxation. It also modulates neurotransmitters like GABA, serotonin, and dopamine, helping the nervous system shift into a relaxed state without sedation.

2. Does L-theanine help you fall asleep or stay asleep?

L-theanine does not act as a sedative but helps reduce mental chatter and stress, making it easier to fall asleep. Research suggests it may also improve sleep quality and efficiency, especially for people with anxiety-related sleep issues.

3. Is L-theanine better than melatonin for sleep?

L-theanine and melatonin work differently. Melatonin regulates the sleep-wake cycle, while L-theanine supports relaxation and nervous system balance. L-theanine may be preferable for people who struggle with racing thoughts or who experience grogginess from melatonin.

4. When is the best time to take L-theanine for sleep?

L-theanine is typically taken 30–60 minutes before bedtime. Some people also use it earlier in the evening to reduce stress and promote a smoother transition into sleep.