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The Scoop on the Top 5 Benefits of L-Theanine

Green tea and matcha contain L-theanine, a health-promoting amino acid.

L-theanine is an amino acid that is found primarily in dietary sources like green tea and matcha. Most often studied for its effects on reducing stress and promoting calmness, L-theanine also supports sleep, immune function, and blood pressure control

In this article, we will discuss what L-theanine is, where it’s found, and the top five health-promoting benefits that it has.

What is L-Theanine?

L-theanine is a unique amino acid commonly found in green tea leaves but is also in smaller amounts in black tea, white tea, and some mushrooms. 

It’s unique in that it doesn’t function as a building block to proteins, as most other amino acids do. It’s not commonly found in foods and is not required by our bodies. Therefore, L-theanine is considered a non-dietary, nonessential amino acid. 

Even though it is deemed nonessential, there are several health-promoting properties associated with L-theanine. The primary benefit of L-theanine is that it stimulates a calm and focused state of mind, relieves stress and promotes calmness, and leads to better sleep

Top 5 Benefits of L-Theanine

1. Promotes a Calm State 

The calming effects of L-theanine stem from its ability to produce the neurotransmitters GABA and dopamine, which have relaxation-promoting qualities. At the same time, L-theanine also reduces levels of glutamate, an excitatory neurotransmitter. It does this by binding to glutamate receptors and increasing GABA, which competes with glutamate’s re-uptake in the brain.

Structurally, L-theanine is very similar to the amino acid glutamine, which produces glutamate. Through L-theanine, the upregulation of GABA can counterbalance glutamate levels. 

Although some glutamate is still needed for a healthy brain, excess amounts can increase stress and agitation. GABA and glutamate have sometimes been referred to as the yin and yang of neurotransmitters, as the combination of the sedative-like properties of GABA and the excitatory nature of glutamate creates a perfect amount of stimulation when in balance.

This yin-yang balance makes L-theanine a natural anxiolytic, a medication or therapeutic intervention that reduces symptoms of unease or agitation. However, unlike prescription anxiolytics, L-theanine can bring on the calm without creating drowsiness. 

Research has also backed up the anxiolytic properties of L-theanine. An October 2019 study published in Nutrients randomized 30 adults to receive either 200 mg per day of supplemental L-theanine or a placebo. Those in the L-theanine group had significantly reduced levels of low mood, stress, and agitation after four weeks.

Another study published in Nutrients found that adults who consumed a beverage containing 200 mg of L-theanine had reductions in their response to a cognitive stress test one hour after drinking it and reductions in salivary cortisol levels three hours later.

L-theanine promotes relaxation and reduces stress

2. Sleep Support

In the October 2019 study in Nutrients, adults who took 200 mg of L-theanine before bed also had significant reductions in sleep latency (the time it takes to fall asleep), sleep disturbances, and usage of sleeping medication throughout the four-week study.

The mechanisms behind how L-theanine benefits sleep are similar to that of its calming properties. Through GABA upregulation, L-theanine promotes a relaxing and calm state to wind down for bed. 

3. Focused Energy and Cognition

Another related benefit of L-theanine is how it promotes a state of wakeful relaxation — the kind of peaceful brain state that you experience during meditation, creative work, or anything that puts you in a flow state. 

L-theanine produces focused energy through its enhancement of alpha brain waves, which are associated with calmness, relaxation, and contentment, but without drowsiness or fatigue. Consumption of L-theanine in combination with caffeine — like green tea and matcha — amplifies the effects on cognition and focus. In a December 2010 trial published in Nutritional Neuroscience, a combination of 97 mg of L-theanine with 40 mg of caffeine led to significant improvements in accuracy during task switching and self-reported alertness and tiredness

Lastly, L-theanine benefits cognition through its ability to increase brain-derived neurotrophic factor (BDNF), a protein that is essential for maintaining and growing new neurons. BDNF is known to be neuroprotective.

4. Blood Pressure Control

L-theanine has been shown to modulate blood pressure through two mechanisms. First, stress can elevate blood pressure by increasing levels of vasoconstricting hormones, and L-theanine is known to reduce stress. 

Secondly, L-theanine can stimulate nitric oxide production, which is a vasodilator that reduces blood pressure. 

A study published in the Journal of Physiological Anthropology found that 200 mg of supplemental L-theanine was able to attenuate blood pressure elevation that was induced by stressful mental tasks. The greatest improvement was seen in people considered “high responders” because they typically have elevated blood pressure in stressful situations. 

While these results are promising for acute blood pressure control, no studies have been done assessing L-theanine’s effects on longer-term blood pressure regulation. 

5. Immune System Support

Lastly, L-theanine may support immune system functioning through its ability to upregulate certain immune cells and decrease pro-inflammatory compounds. L-theanine has been shown to enhance the innate immune system, our body’s first line of defense against pathogens, through regulation of cytokines.  

A common combination used in studies on immune function is L-theanine with L-cysteine, another amino acid. Research has shown that this combination is linked to improved immune function in endurance athletes as well and the elderly population. 

Although more research still needs to be done on the effects of L-theanine on immunity, the results so far are encouraging.

Side Effects, Dosage, and How to Take It 

Although you can get L-theanine from green tea and matcha, more benefits are seen with higher amounts found in supplements. Matcha, a powder made up of green tea leaves, has higher L-theanine than green tea, which is just the water that the tea leaves were steeped in.

One cup of tea contains approximately 25 mg of L-theanine, whereas supplements range from 50 to 200 mg. In the studies mentioned in this article, 200 mg of L-theanine per day was the most common dosage. 

Whether you’re drinking tea or taking a supplement, L-theanine has been shown to cross over the blood-brain barrier and take effect within 30 to 120 minutes of ingesting it. 

There are no major side effects reported with L-theanine usage. However, people taking blood pressure medications may want to be careful due to the potential blood pressure-lowering effects of L-theanine. 

If you are pregnant, breastfeeding, or tend to have low blood pressure, ask your doctor before consuming L-theanine in supplemental form. 

Key Takeaways

  • L-theanine, an amino acid found in green tea, matcha, and supplements, has been well-studied for its effects on reducing stress, promoting calmness, improving sleep, and providing focused energy. 
  • Other benefits include L-theanine’s ability to modulate blood pressure and support immune function, although more studies are needed. 
  • Supplemental L-theanine is generally considered safe. Research suggests 200 mg is a recommended dose to see benefits. 


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