L-theanine Dosage, Usage, Reviews & Where to Buy


In this article you will find out everything there is to know about L-theanine. This includes sections on “what is L-theanine?”, “how does L-theanine work?”, “L-theanine benefits” , “recommended dosage and usage of L-theanine”, “L-theanine benefits”, “L-theanine side effects” and “where to buy”.

Tea is the second most popular beverage in the world. People have been consuming it for health reasons, religious rituals or plain enjoyment for as long as we can remember. However, it has been discovered only recently that tea leaves (Camellia sinensis) contain a nonessential amino acid called L-theanine (γ-glutamylethylamide).

Scientists took interest in L-theanine in 1949, when they established that it is an ingredient of green tea. A year later Japanese scientists extracted it in a laboratory. Soon after that L-theanine found its way into the food and supplement industry. It is now believed that L-theanine gives tea its distinctive aroma and umami taste.

L-theanine is a naturally occurring non-dietary amino acid (not required in the diet to support life functions), that plays a very important role in our bodies. A growing body of literature demonstrates that L-theanine may have anxiolytic effects (i.e. reduces stress levels). In addition, it has been found to have a positive effect on cognition and mood. Interestingly, it helps users to relax without sedation.

How does L-theanine work?

After oral ingestion, L-theanine is quickly absorbed into the bloodstream. It is then transported to the brain where it crosses the blood-brain barrier within 30 minutes. It reaches a maximum concentration in about 2 hours and 24 hours later it is removed from the body. As it is able to pass the blood-brain barrier it affects the brain directly.

Briefly, L-theanine modulates the brain activity as demonstrated by the electroencephalograph (EEG) studies. These studies show that brain waves are smoothed out which causes a relaxed yet alert mental state.

It is structurally very similar to Glutamine (an essential amino acid), that is a precursor to GABA and glutamate neurotransmitters. L-theanine changes the levels of amino acids that are important for the release of serotonin neurotransmitter. Serotonin is a primary factor regulating our mood. Adequate levels of serotonin are important for a stable and generally healthy mood.

Usage tips:

Although this compound is effective on its own, it is also widely used in stacks. Usually it is combined with other popular stimulants and enhancers, such as Piracetam or caffeine. Interestingly, L-theanine lessens the side effects of caffeine.

“That is why L-theanine is a synergistic with caffeine in improving cognition and attention.”

Several well-controlled studies examined the additive effect of caffeine and L-theanine. They found positive results, mostly associated with enhanced cognition, improved mood and the ability to cope with stress.

Due to the effectiveness of such combination, some beverage manufacturers believe that the next generation of drinks will include L-theanine alongside commonly used central nervous stimulants, like taurine and caffeine. Such drink would have a great effect on focus and concentration.

  • Stress Relief and Mood enhancer
  • Elevated concentration and mental alertness
  • Immune System and memory support

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 L-theanine benefits:

One of the main reported benefits of L-theanine is that it puts its users “in the zone” by increasing the levels of alertness. However, this effect lasts only for a relatively short period, which means that, unlike some popular stimulants, L-theanine would not keep you up all night.

“L-theanine is particularly effective in individuals with high levels of anxiety.”

It also has positive effects on physical and mental stress levels by promoting relaxation and calmness. In terms of physical signs, it may result in a reduced heart rate and lower blood pressure and even promote weight loss. Improved concentration and learning abilities are associated with the ability to remove external distractions and focus only on the tasks at hand.

Scientific evidence on L-theanine effects:

A number of studies have demonstrated that L-theanine has anxiolytic effects (i.e., anxiety reduction).1,2 This has some very important practical implications as those suffering from different types of anxiety (e.g., social anxiety) can benefit from using L-theanine supplements. L-theanine is best known for its relaxing properties without sedation. In other words, it would you help relax without making you sleepy.

In addition to its anxiolytic effects, L-theanine improves concentration and learning abilities. Participants were more efficient at removing external distractions and focusing only on the tasks at hand (i.e., increased selective attention) following the use of L-theanine.3

Interestingly, a greater enhancement in cognitive function is demonstrated when L-theanine is co-administered with caffeine as these two substances appear to be synergistic (see below for more information on recommended dosages). For example, a combination of L-theanine and caffeine has been shown to have an additive effect on attention in healthy male volunteers when taken in high doses.3

There is also some scientific evidence to suggest that L-theanine positively alters physiological signs reported under stress. For example, a study by Kimura et al.1 demonstrated a lower heart rate and salivary immunoglobulin A (s-IgA) following an acute stress task. These physiological signs can be linked to a reduced sympathetic nervous activity.

Other studies show that L-theanine may be effective at promoting weight loss, strengthening immune system and even preventing from certain cancers and cardiovascular diseases.4

Recommended L-Theanine dosage:

L-Theanine is typically taken in 100 to 200 mg doses, usually with caffeine. It is not recommended to use it while breast feeding. As with any other supplement, if you have any concerns about taking L-Theanine, it is recommended that you speak to a health professional.

L-Theanine side effects:

L-Theanine is the FDA-approved compound, meaning it is safe for human consumption. Even though your morning tea contains it, the desired effects come with significantly higher doses.

As far as side effects are concerned, only a very small number of studies have reported any negative effects. It is mostly related to a lowered blood pressure. Therefore extra care must be taken by those who take any type of high blood pressure (hypertension) medication. Combined with L-Theanine, it may drop the blood pressure to a dangerous level.

In general, L-Theanine is safe to take even at extended, frequent rates of use. Users of L-theanine do not develop chemical dependence.

Where can I buy L-Theanine online?

ThoughtFoods.co.uk, ThoughtFoods.com and ThoughtFoods.eu sell L-theanine capsules (120 x 200 mg) for £14.75, $21.09 and €19.32, respectively. They also provide customers with a great option by selling sachets of L-theanine (and other nootropics) so they can try and see if it works for them before buying larger quantities. A sachet of 6 capsules x 200 mg costs £6.89, $9.85 and €9.03, respectively.


  1. Kimura, K. et al. (2007). L-theanine reduces psychological and physiological stress responses, Biol Psychol. 74 (1), 39-45.
  2. White, D.J. et al. (2016). Anti-stress, behavioural and magnetoencephalography effects of an L-theanine-based nutrient drink: a randomised, double-blind, placebo-controlled, cross-over trial, Nutrients. 8 (1).
  3. Kahathuduwa, C.N et al. (2016). Acute effects of theanine, caffeine and theanine-caffeine combination on attention, Nutr Neurosci. [Epub ahead of print].
  4. Vuong, Q.V. et al. (2011). L-theanine: properties, synthesis and isolation from tea, J Sci Food Agric. 91 (11), 1931-9.