What is L-theanine?

L-theanine is a nondietary amino acid that cannot be produced by the body and found in plant and fungal species. L theanine was first discovered in the 1940s and not much is known prior to its discovery. It is easily able to cross the blood–brain barrier which makes it a potent amino acid that can help with many ailments.

Health Benefits of L-theanine

Improve brain health

L-theanine increases serotonin, dopamine, GABA, and glycine levels in various areas of the brain and can help improve memory

Relieve stress and anxiety

L-theanine has been clinically proven to promote an alert state of relaxation without causing drowsiness. It can help increase performance under stress and decrease anxiety.

Increases brain alpha waves

Alpha brain waves are common in meditative states and can help with meditation practices.

Some studies have also shown that L-theanine can help with high blood pressure, prevent Alzheimer's disease, and for make cancer drugs more effective.

Help with focusing and multi tasking

Numerous studies have concluded that taking L-theanine and caffeine improves the ability to multi-task and reduces task-induced fatigue. However it is best to avoid caffeine if you are having problems sleeping or suffering from insomnia.

Reduce menstrual discomfort

Improve sleep conditions such as Insomnia

Although l theanine is not sedative despite its relaxing effects it can improve the quality of sleep.

Food sources of L theanine

L-theanine is found in black, green, and white teas from Camellia sinensis. however in order to extract enough l-theanine you will need to drink several cups of excellent quality tea which can be difficult to source as different teas will have varying amounts.

Green tea contains l theanine however in order to extract enough l-theanine you will need to drink several cups of excellent quality green tea.

Agonist / synergist

Caffeine - in combination with caffeine, L-theanine can work synergistically


None known

There is no set RDA for L-theanine and it is not required in the diet to support life.

L-theanine Supplementation

L-theanine is available as a supplement, the recommended dosage is usually 200mg and is dependent on body weight. It is ideal to take the supplement a few hours before sleep.

How to use L-theanine

Although you can get L-theanine from black or green tea you would need to drink high amounts and quality tea for the amount required to achieve some of the positive results of L-theanine. L-theanine extracted from green tea is now available in powder or capsule form. It is recommended to only take the minimum amount effective for the various health benefits and conditions that L-theanine can help with.

Suppress the negative side effects of caffeine

Coffee can cause several negative side effects such as headaches and jitters associated with caffeine which can be reduced by combining L-theanine in a cup of coffee or simply take L-theanine in water or juice a while after drinking coffee and avoid the negative side effects.

Improve your concentration

To improve your concentration, focus and alertness numerous studies have shown that you will need a caffeine and L-theanine ratio of 1:2. Caffeine is also available for supplementing in powder or capsule form. If you are having sleep problems it is best to avoid caffeine altogether.

Deficiency Symptoms of L-theanine

There are no specific deficiency symptoms of L-theanine although it can help other deficiency symptoms which includes deficiency symptoms of GABA an essential neurotransmitter. Some of the following deficiency symptoms of GABA can be helped by supplementing with L-theanine

  • Depression
  • Anxiety
  • Stress
  • Nervousness
  • Panic
  • Insomnia
  • ADHD or Attention Deficit Hyperactivity Disorder

Toxicity Symptoms of L-theanine

No known toxicity for L-theanine. However high and unnecessary amounts can have negative side effects. L-theanine has the potential to increase serotonin levels and can cause incredibly high levels of serotonin which can cause adverse symptoms, although studies have shown increases and decreases in serotonin levels which may be associated with the various factors, such as weight, health of person and other factors such as the time of consumption.