Evidence supporting the use of: L-theanine
For the health condition: Mood Swings

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-theanine is an amino acid commonly found in tea leaves, especially green tea, and is widely used as a dietary supplement for its calming properties. Scientific studies suggest that L-theanine may promote relaxation and reduce stress without causing drowsiness, primarily through its effects on neurotransmitters such as GABA, dopamine, and serotonin. These neurotransmitters play key roles in regulating mood and emotional stability. Some research indicates that L-theanine supplementation can help reduce symptoms of anxiety and improve subjective feelings of well-being, which may indirectly help with mood swings. For example, a randomized controlled trial published in Nutrients (2019) found that L-theanine supplementation reduced stress-related symptoms and improved sleep quality in healthy adults.

However, direct evidence for L-theanine specifically treating "mood swings" (as opposed to general anxiety, stress, or mood) is limited. Most clinical trials focus on acute stress and anxiety reduction rather than the broader and more complex phenomenon of mood swings, which can have various underlying causes. While its calming effects may theoretically stabilize mood fluctuations, more targeted research is needed to establish its efficacy for this specific condition. Thus, while its use is grounded in scientific research related to mood regulation, the evidence directly supporting L-theanine for treating or preventing mood swings is still considered preliminary (rated 2 out of 5).

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