Potential Benefits of Theanine & Its Impact on Health
By Dr Rajeev Singh +2 more
Medically reviewed by Dr Rajeev Singh
Last updated: Jan 2, 2026 Published on: Jul 2, 2024
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By Dr Rajeev Singh +2 more
Table of Contents
L-Theanine is a unique natural compound, attracting much attention for its potential health benefits. Originating from green and black tea leaves, this bliss-inducing amino acid has become an increasingly popular supplement in recent years. Inquisitive researchers have explored L-theanine’s numerous effects on our health and well-being, with considerable interest focusing on its calming and anxiety-reducing properties4.
In this article, we will explore the fascinating world of L-theanine, its science-backed potential benefits, possible side effects, safety considerations, ideal dosages, and frequently asked questions.
L-Theanine is a non-protein amino acid10. It’s a key reason why tea has a calming and soothing effect. You can find it in both green and black tea. The proposed benefits cover a wide range from reducing stress to boosting brain function. Unlike many amino acids, L-theanine can cross the blood-brain barrier efficiently. This ability is said to enhance its impact on mood and cognition2.
Green and black teas are the main L-theanine sources4. Some types of mushrooms also have this special amino acid. Despite this, the easiest way for most people to get its benefits is by either drinking tea or taking L-theanine supplements.
L-theanine is proposed to reduce anxiety and help us relax. Their potential effect on health is discussed in detail in the section below.
L-theanine is famous for promoting relaxation. Research shows it can fight anxiety and stress. It does this by reshaping the brain’s neurotransmitters called serotonin, dopamine, and GABA. It is proposed to promote GABA which is an inhibitory neurotransmitter that slows done electrical signals in the brain. As a result, L-theanine may produce alpha-wave brain activity, which is linked to calmness, thus softening the blows of stress and reducing anxiety1. More robust scientific studies are needed to explore this proposed effect of L-theanine on brain activity. If you are considering using it to feel calmer or less anxious it is always advised to run it by your doctor before doing so.
L-theanine doesn’t merely combat anxiety. Research supports its role in boosting focus, attention, and cognitive function2. It seems particularly powerful when paired with caffeine.
L-theanine’s anxiety-relieving property is also said to enhance sleep. Research found that it helps people unwind before bed, fall asleep quicker, and enjoy more profound sleep.
L-theanine found in green tea may influence weight loss and metabolism. Green tea has compounds like catechins that boost metabolism3. L-theanine contributes to its distinctive savoury taste (umami flavour).
It is to be noted that green tea may be incorporated in your weight loss journey as an aid to regular exercise and a balanced diet, under the guidance of a healthcare professional.
The immune-boosting nature of L-theanine is proposed to support overall health. Studies have shown that L-theanine may increase the body’s natural defense against ailments like colds and flu.
Recent research highlights the beneficial effects of L-theanine on liver health. Studies have shown that L-theanine, when added to the drinking water of rats with liver cirrhosis, reduces inflammation and fibrosis by lowering harmful cytokines and increasing beneficial ones.These findings suggest that L-theanine might be a promising supplement for supporting liver health and preventing damage.
Dr. Nayana Shetty, MBBS, MD
High blood pressure comes with countless health risks. By promoting relaxation and reducing heart rates, L-theanine’s stress-reduction properties may aid in lowering the blood pressure5.
How L-theanine Affects Blood Pressure Regulation: Through its impact on neurotransmitters, namely GABA, L-theanine lowers blood pressure. By boosting GABA levels, it relaxes blood vessels, decreases heart rates, and ultimately lowers blood pressure. More robust research is required to corroborate these findings.
There are signs that L-theanine may help in the case of cancer. Various studies showed that it might enhance the impact of certain chemotherapy drugs and reduce cancer therapy side effects7.
It is to be noted that it may aid the cancer therapy but is not a substitute for it and you may add this under the guidance of your treating doctor. Also, though studies have shown its potential benefits in cancer therapy, further large scale trials are needed to confirm these.
Theanine might also be good for your kidneys. In studies with rats, L-theanine helped protect kidneys from damage caused by doxorubicin, a chemotherapy drug. It reduced harmful oxidative stress and improved kidney function.
Dr. Nayana Shetty, MBBS, MD
Although L-theanine has been recognised as generally safe, it’s important to understand any potential side effects or interactions with medications and other supplements.
Most people tolerate L-theanine well with very few reported side effects. However, there may be instances where its use should be carefully used or avoided.
The best dose of L-theanine may differ based on individual factors and the benefits you want. Always consult a healthcare professional before starting any new supplement, including L-theanine.
The dosages mentioned below are the ones which have been studied but the response may differ from person to person:
Always remember never to self-administrate, incorporate it only under the guidance of a healthcare professional.
Factors like age, weight, and health status can determine a person’s ideal L-theanine dose. Also, everyone’s response to it can differ. Always consult a healthcare professional to get advice on L-theanine dosages.
L-theanine’s calming and anxiety-subduing properties, coupled with its potential benefits for sleep, cognitive performance, and overall health, make it an interesting natural option for those wanting to boost their well-being. Even though research has shown promising results up until now, more studies are needed to confirm L-theanine’s health benefits.
Always ask your healthcare professional’s advice before taking L-theanine supplements. They will help decide the best dosage for you and check for safety. With the right guidance, L-theanine might add value to your health.
Though there’s anecdotal and therapeutic evidence that L-theanine can lessen anxiety and stress1, always discuss it with a healthcare professional before using it as a standalone management option for these issues. Always remember that self-medicating is not encouraged or advisable.
Both L-theanine and caffeine may help boost focus and attention8. But unlike caffeine, L-theanine achieves this without the jitteriness or addiction potential that comes with stimulants.
There’s currently no evidence that L-theanine is unsafe for long-term use, especially if consumed through tea. However, always remember to consult with a healthcare professional before taking any supplement for a long time.
Absolutely, but safety is first. Always check in with a healthcare professional before combining L-theanine with other supplements or medications to avoid possible interactions. If you are thinking of mixing L-theanine with blood pressure or anxiety medications and supplements, or stimulants, it is advised not to due to drug interactions.
Pregnant or breastfeeding women, as well as those with a history of low blood pressure, should avoid L-theanine.
Disclaimer: The information provided here is for educational/awareness purposes only and is not intended to be a substitute for medical treatment by a healthcare professional and should not be relied upon to diagnose or treat any medical condition. The reader should consult a registered medical practitioner to determine the appropriateness of the information and before consuming any medication. PharmEasy does not provide any guarantee or warranty (express or implied) regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of the information; and disclaims any liability arising thereof.
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