L-theanine, an amino acid found in tea leaves, helps reduce stress, promote relaxation and improve the quality of sleep. L-theanine is found in tea leaves in low concentrations (less than 2 percent), which means that effective dosage levels (of 100 – 200mg/day) cannot be delivered from drinking tea. Recently, animal studies and human studies have shown that a high dose of L-theanine (100 mg) combined with caffeine about at the level of a single cup of tea (40 mg), can help to improve attention, memory, and cognition.


L-Theanine Actions

There is no question that caffeine increases alertness, but this effect comes at a price. L-Theanine appears to counteract some of the stimulatory effects of caffeine while exerting benefits of its own. Some of the effects noted for L-theanine include:

  • Increasing brain serotonin, dopamine, and GABA levels.
  • Binding to various brain receptor sites.
  • Improving learning and memory in animal studies.
  • Positive results in double-blind studies showing it:
    • Reducing feelings of stress.
    • Improves the quality of sleep.
    • Diminishes the symptoms of the premenstrual syndrome
    • Increasing the production of alpha brain waves

L-theanine is a very is a popular ingredient in function foods and beverages as well as dietary supplements designed to produce mental and physical relaxation, without inducing drowsiness.


New Data

In a study of 91 subjects with mild cognitive impairment (MCI), subjects were given either the green tea-theanine combination or a placebo. Neuropsychological tests (Rey-Kim memory test and Stroop color-word test) and electroencephalography (EEG) were conducted to evaluate the effect of green tea-theanine on memory and attention. The results demonstrated that the green tea-theanine product led to improvements in memory and attention. The EEG tracings indicated an increase in brain theta waves, an indicator of cognitive alertness.



Park SK, Jung IC, Lee WK, et al. A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study. J Med Food. 2011 Apr;14(4):334-43.

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