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Theanine, or l-theanine, is a relaxing and nondietary amino acid found pretty much exclusively in teas. L-theanine travels to the brain after being consumed orally, where it promotes relaxation without sedation and helps reduce stress, while also helping moderately with attention. L-theanine may also help with sleep to some extent. When taken with caffeine, L-theanine may be effective in helping with cognition and promoting attention. Some of the benefits that have been attributed to green and black tea consumption may actually be due to their theanine content.

Also known as:  2-Amino-4- (ethylcarbamoyl) Butyric Acid, Gamma-glutamylethylamide, L-Theanine, L-Théanine, N-Éthyl-L-Glutamine, Teanina, Théanine

Diseases and Conditions

Theanine is possibly effective for cognitive performance. There is insufficient information on its effectiveness for attention-deficit hyperactivity disorder (ADHD), influenza, stress, and other conditions.


Theanine is possibly safe when used orally and appropriately, for up to 3 weeks. It is possibly safe for children to take theanine orally under the supervision of a physician. There is insufficient information on the safety of theanine for pregnant and breastfeeding women, therefore it is best to avoid. Orally, theanine is generally well-tolerated although rare side effects may include headaches and facial tics.

Medication Interactions

Using theanine with antihypertensive drugs may potentiate the activity of antihypertensive drugs. Some antihypertensive drugs include:

  • Captopril (Capoten)
  • Enalapril (Vasotec)
  • Losartan (Cozaar)
  • Valsartan (Diovan)
  • Diltiazem (Cardizem)
  • Amlodipine (Norvasc)
  • Hydrochlorothiazide (HydroDiuril)
  • Furosemide (Lasix)

Using theanine concomitantly with stimulant drugs may decrease the effects of stimulant drugs. Some stimulant drugs include:

  • Diethylpropion (Tenuate)
  • Epinephrine
  • Phentermine (Ionamin)
  • Pseudoephedrine (Sudafed)

Supplement and Food Interactions

Theanin may interfere with herbs and supplements which contain caffeine or have hypotensive properties.


A common dose of theanine is 100-200 mg. Some people may take l-theanine simultaneously with caffeine consumption. The exact amount of l-theanine that is right for you depends on a variety of factors including age, gender, and health conditions.


Food sources of l-theanine include:

  • Green Tea
  • Black Tea
  • White Tea (250-60 mg of l-theanine per 200 mL serving of tea)
  • C. japonica and C. sasanqua
  • A type of mushroom called Xerocomus badius

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