Evidence supporting the use of: L-theanine
For the health condition: Thinking (cloudy)

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Synopsis

Source of validity: Scientific
Rating (out of 5): 3

L-theanine is an amino acid primarily found in green tea, well-known for its calming effects. There is a moderate level of scientific evidence supporting its use for improving cognitive performance and reducing "cloudy thinking" or mental fog. Several double-blind, placebo-controlled studies have shown that L-theanine can enhance attention, reaction time, and working memory, particularly under conditions of stress or anxiety, which are common contributors to cognitive cloudiness. Mechanistically, L-theanine is believed to cross the blood-brain barrier and modulate levels of neurotransmitters such as dopamine, serotonin, and GABA, promoting a state of relaxed alertness without sedation. Functional MRI studies have also demonstrated that L-theanine can increase alpha wave activity in the brain, which is associated with a calm yet alert mental state. While L-theanine is not a treatment for underlying medical causes of cognitive impairment, its use as a nootropic supplement for supporting mental clarity and reducing the sensation of "brain fog" is supported by a growing, though not definitive, body of clinical research. Most studies use doses of 100–200 mg, with effects noticeable within an hour and lasting several hours. However, further large-scale trials are needed to confirm the magnitude and consistency of these effects across different populations and to compare efficacy with other cognitive enhancers.

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