L-theanine is an amino acid known for promoting a calm focus without making you feel sleepy or drowsy. It’s found naturally in matcha and green tea but has recently gained popularity as a supplement. People have been using it to take the edge off, help with sleep, and sharpen mental clarity.
Learn more about the potential benefits, possible risks, and ways you can increase L-theanine in your diet naturally.
What is L-theanine
L-theanine is a naturally occurring amino acid primarily found in some teas and a few varieties of mushrooms. It’s considered a non-essential amino acid. The body cannot produce it, which is not considered essential for health. You may see it written as L-theanine or just theanine, but they are used interchangeably. You may also see D-theanine, which is considered the chemical “mirror image” of L-theanine (in other words, a different form of theanine) and is not as well studied as L-theanine. Some studies suggest that D-theanine may actually block the absorption of L-theanine.
L-theanine was first discovered in the mid-20th century and is now widely studied for its effects on the brain and nervous system. Unlike other amino acids, which are used by the body to build proteins, L-theanine acts more like a neuromodulator- meaning it influences how we feel, think, and respond to stress. Because of this, it has gained traction in the wellness world as a supplement to help improve memory and focus, promote relaxation, and enhance mood.
One thing that makes L-theanine special is that it can easily cross the blood-brain barrier and directly influence brain function. It may interact with neurotransmitters, such as GABA, serotonin, and dopamine, which help regulate mood, sleep, and stress. It has also been shown to block glutamate, an excitatory neurotransmitter, which, in excess, may contribute to feeling anxious or overstimulated. This may be why L-theanine has been known to promote relaxation without making you feel drowsy.
Possible Benefits
Improved focus
L-theanine is thought to help promote alpha brain wave activity, which may help support a state of calm alertness. Paired with caffeine (as in green tea), it can enhance attention and cognitive performance without making you feel jittery.
Blood pressure management
Some studies suggest that L-theanine may help reduce blood pressure, particularly during stressful situations- like getting your blood pressure taken at the doctor's or when taking a test. This may be thanks to its ability to dampen the body’s stress response.
Better memory
L-theanine has been linked to improved memory and better mental clarity, especially when paired with caffeine. One study found that adults who regularly drank green tea for 12 weeks had improved attentional function and working memory. However, the study authors stated that more research is needed to fully understand this.
Improved sleep
L-theanine has been shown to promote relaxation, which can help the body wind down and fall asleep naturally. Regularly consuming L-theanine has also been shown to improve sleep quality, especially for anyone who suffers from anxiety or racing thoughts.
Relaxation
One of the most well-known benefits of L-theanine is its ability to help you feel more relaxed and at ease. Research shows it does this by increasing the levels of calming neurotransmitters like GABA and dopamine while also increasing alpha brain wave activity, overall helping you feel calmer.
Improved immunity
Some studies suggest that L-theanine can enhance the immune system by improving the activity of specific white blood cells, particularly when consumed regularly in tea. These are just preliminary studies, though, so more research is still needed.
Potential risks and side effects
The FDA classifies L-theanine as “generally recognized as safe,” and it is well tolerated by most people. However, it can interfere with certain medications and is not recommended for anyone who is pregnant or breastfeeding. Some people may also experience mild dizziness and digestive discomfort—although both are rare side effects. In general, more research is needed, but there are no confirmed side effects of consuming L-theanine.
When consumed through natural sources like tea, these minimal side effects can be even less. Still, it’s always best to ask your healthcare provider before taking any supplement.
Natural sources of L-theanine
If you feel wary of supplements, tea, especially green tea, is the most abundant natural source of L-theanine. Because matcha is made from shade-grown green tea leaves, a cultivation method that boosts the plant’s L-theanine content, matcha stands out as one of the richest sources of L-theanine. When drinking matcha, you also consume the entire tea leaf, making it a more bioavailable and potent source compared to regular steeped tea.
Other teas, such as black, white, and oolong, do contain some L-theanine but in lower concentrations. The specific amount found in tea varies depending on growing methods, harvest time, and how the tea is processed, so it’s important to look for high-quality tea. Herbal teas, such as chamomile or rooibos, are not sources of L-theanine.
Another perk of choosing natural sources, such as matcha, is that the benefits are twofold: not only do you get L-theanine, but you also get the benefits of caffeine (in an ideal amount), antioxidants like EGCG, and chlorophyll. These compounds can create a smoother and more balanced effect on mood and health compared to isolated supplements.
Bottom Line
L-theanine is a powerful amino acid that can help you feel relaxed and improve mental clarity and focus. While supplements can be convenient and are likely quite safe, L-theanine is found naturally in tea, especially matcha green tea. It works in harmony with caffeine and antioxidants to create a state of relaxed alertness.
Disclaimer: These statements in this blog post have not been evaluated by the Food and Drug Administration. The information provided here is for educational purposes only and should not be considered as medical advice. It's essential to consult with a qualified healthcare professional before making any dietary or lifestyle changes
Resources:
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