Theanine
Theanine is an amino acid from tea. A systematic review of randomised studies concludes that 200 to 400 mg per day can reduce stress and anxiety in people under stressful conditions.
What the research shows
Shown, with a clear condition or a limited scope.
The 2020 systematic review from the University of Canberra went through nine randomised trials and finds less stress and tension at 200 to 400 mg per day in situations of acute pressure, while for chronic anxiety the picture stays empty. The 2025 review with meta-analysis screened fifty randomised trials, fifteen of which entered the calculation, and found small effects on choice reaction time, attention and mood, mostly in combination with caffeine, with confidence intervals that often run through zero. Who paid matters here: the 2019 Japanese trial came from theanine supplier Taiyo Kagaku with two employees as co-authors, and the 2025 meta-analysis was partly funded by Lipton Teas and Infusions. The independent review points the same way, only the effect is small.
Who it makes sense for: Mainly for people who tolerate caffeine poorly: taken together with caffeine, the jitters and the racing heart get milder while attention holds up. For strength, endurance or muscle growth nothing has been measured. Studies use 200 to 400 mg, usually at roughly a 1 to 1 or 2 to 1 ratio with caffeine, so under 100 mg per serving it is decoration.
How we weigh evidenceClinical dosage
Origin
NaturalL-theanine is found almost exclusively in tea leaves (Camellia sinensis). Green tea has the highest concentrations. In supplements extracted from tea or produced via fermentation.
Safety
Broad safety profile, people have been drinking tea for centuries. Studies with theanine alone show no sedating effect, though drowsiness is rarely measured as an outcome. In a four-week study, 200 mg per day also improved sleep quality. No known side effects.
For comparison
A cup of green tea contains 25-50mg of theanine. For 200mg (a typical supplement dose) you'd need to drink 4-8 cups of tea. The caffeine + theanine combo is what makes tea feel smoother than coffee.
Dosage by weight and gender
The effective theanine dose is 100-200mg per intake, regardless of body weight (Nobre et al., 2008). The optimal ratio with caffeine is 2:1 (e.g. 200mg theanine with 100mg caffeine). There are no differences in effect between men and women. Higher doses up to 400mg are also safely tolerated but don't necessarily provide more benefit.
Frequently asked questions
What is theanine?
Theanine is an amino acid from tea leaves that promotes a relaxed but alert mental state. It reduces the negative effects of caffeine (nervousness, jitters) without reducing focus.
Is theanine dangerous?
No, theanine is one of the safest supplements out there. People have been drinking tea for thousands of years without issues. There are no known side effects, even at higher doses.
How much theanine per day?
Take 100-200mg theanine per serving. For the best synergy with caffeine, use a 2:1 ratio: 200mg theanine with 100mg caffeine. You can take it multiple times per day.
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic ReviewWilliams JL et al. (2020)
- Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled TrialHidese S et al. (2019)Funded by: Gefinancierd door Taiyo Kagaku uit Mie, dat de theanine- en placebotabletten leverde; twee auteurs zijn werknemer van dat bedrijf.
- Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled TrialsPayne ER et al. (2025)Funded by: De promotieplaats van de eerste auteur wordt betaald door Lipton Teas and Infusions, een auteur is werknemer van Lipton en een van Unilever; daarnaast financiering van de Schotse overheid (RESAS).
Pre-workouts with Theanine
MuscleTech VaporX5 Next Gen
Pre-workout from MuscleTech with a nine gram scoop and thirty servings in a 266 gram tub. At two scoops the label lists three grams of creatine monohydrate, 3.2 grams of beta-alanine, 2.5 grams of betaine and 1.5 grams of Nitrosigine, plus caffeine. MuscleTech itself says to start at half a dose.
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.