L-theanine: what it is, what research shows and how to take it
L-theanine is an amino acid found naturally in tea leaves. It is the reason many people say that tea has a different calming effect from coffee, even though both drinks contain caffeine.
In this article you will learn what the research actually shows, how L-theanine is combined with caffeine and who should discuss it with a doctor.
In brief. There is no authorised claim for L-theanine supplements that would allow a specific effect to be promised.1 The studies are small: in some of them, 200–400 mg per day reduced the feeling of tension in people experiencing stress.2 Theanine is well tolerated by most adults.3
What is L-theanine?
L-theanine is not one of the amino acids from which the body makes proteins. It is found almost exclusively in tea and in some mushrooms.3 A cup of tea usually contains considerably less theanine than a single supplement capsule.
Example. If a capsule contains 200 mg of theanine, you would need to drink many cups of tea to get the same amount. You would also take in a lot of caffeine.
What does the research show?
Tension. In a review of 9 studies, 200–400 mg of theanine per day reduced the feeling of stress and anxiety in some studies in people who were experiencing tension.2 The studies were small and varied, so firm conclusions cannot be drawn.
Sleep. In a study, 30 healthy adults took 200 mg of theanine per day or a placebo for 4 weeks. In the theanine group, some self-rated measures of sleep quality improved.4
Attention with caffeine. In a study with 27 adults, 100 mg of theanine together with 50 mg of caffeine improved results in some attention tasks.5
What this means for you. Theanine may be a gentle option if you would like to feel calmer during a stressful period. However, it is not a medicine for anxiety or insomnia. If these difficulties last longer, see a doctor.
How to take L-theanine?
| Situation | How it is most often used in studies |
|---|---|
| Stressful period | 200–400 mg per day2 |
| In the evening, before bed | 200 mg4 |
| With coffee or tea | About 100 mg of theanine together with caffeine5 |
In studies, theanine generally did not cause strong drowsiness, which is why it is often taken during the day as well.2 Nevertheless, follow the dose indicated by the manufacturer.
Add it up. Theanine is often found in blends for "sleep" or "focus" and in pre-workout products. Check the composition of all the products you take.
How to choose an L-theanine product?
- Look at the amount of theanine per capsule. Products contain from 100 to 200 mg. It is more convenient to start with a lower dose.
- Pure or with additional ingredients. Some products combine theanine with inositol, GABA or plant extracts. If you want to know how theanine itself works, choose a pure product.
- Suntheanine is the brand name of a theanine raw material. It is the same substance – L-theanine.
Who should be cautious?
- You are pregnant or breastfeeding – there is insufficient safety data.3
- You take medicines that lower blood pressure – theanine may lower it further.3
- You take sedatives or sleeping pills.3
- You want to give the supplement to a child.
Side effects are rare. Some people experience headache or nausea.3
Selected L-theanine products
Commercial information. These are products available in our shop. This is not a ranking of effectiveness. Before buying, check the composition and instructions for use on the product page.
Theanine, 100mg - 60 vcaps - Jarrow Formulas
100 mg of L-theanine per capsule, vegetable capsule. The lower dose is convenient for beginners or when combining with coffee.6
L-Theanine with Suntheanine, 150mg - 90 vcaps - Doctor's Best
150 mg of L-theanine (Suntheanine) per capsule. The manufacturer recommends 1 capsule per day without food.7
Double Strength L-Theanine, 200mg - 60 vcaps - NOW Foods
Each capsule contains 200 mg of L-theanine and 100 mg of inositol. The manufacturer recommends 1 capsule 1–2 times per day, preferably on an empty stomach.8
L-Theanine, Pure Powder - 28g - NOW Foods
Pure L-theanine powder, 285 mg per ⅛ teaspoon serving. The serving is very small, so it is difficult to weigh accurately. Dissolve in water or juice.9
Frequently asked questions
Does theanine cause drowsiness?
Usually not. That is precisely why it is often taken during the day.2 If you feel drowsy, do not drive until you know how it affects you.
Can theanine be taken together with coffee?
Yes, this combination is often studied.5 Just add up all the caffeine you get during the day from coffee, tea, energy drinks and supplements.
How long can theanine be taken?
In studies, theanine was most often taken for periods ranging from one day to several weeks.2 Discuss longer-term use with a doctor or pharmacist.
Scientific sources
- EFSA NDA Panel. Scientific opinion on the substantiation of health claims related to L-theanine from Camellia sinensis (L.) Kuntze (tea) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal. 2011;9(6):2238. doi:10.2903/j.efsa.2011.2238
- Williams JL, Everett JM, D'Cunha NM et al. The effects of green tea amino acid L-theanine consumption on the ability to manage stress and anxiety levels: a systematic review. Plant Foods Hum Nutr. 2020;75(1):12–23. doi:10.1007/s11130-019-00771-5
- MedlinePlus, U.S. National Library of Medicine. Theanine. medlineplus.gov
- Hidese S, Ogawa S, Ota M et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. doi:10.3390/nu11102362
- Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008;11(4):193–198. doi:10.1179/147683008X301513
- Jarrow Formulas. Theanine, 100 mg, 60 capsules. Product label.
- Doctor's Best. L-Theanine with Suntheanine, 150 mg, 90 capsules. Product label.
- NOW Foods. Double Strength L-Theanine, 200 mg, 60 capsules. Product label.
- NOW Foods. L-Theanine, Pure Powder, 28 g. Product label.
Disclaimer. This article is for informational purposes only and does not replace consultation with a doctor or pharmacist. Dietary supplements are not intended to treat or prevent diseases and are not a substitute for a varied diet and a healthy lifestyle. Before taking supplements, especially during pregnancy or breastfeeding, if you have a chronic condition or if you are taking medicines, consult a healthcare professional.
