Black and green teas including matcha exhibit various levels of L-theanine
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L-theanine is a naturally occurring amino acid found in tea leaves. Its association with the calming effects of tea dates back to the 1940s, and it is now available as a supplement aimed at alleviating stress, enhancing focus, and improving sleep quality. Although studies on its effectiveness are still somewhat limited, there are intriguing insights that may suggest advantages for brain health, particularly for those experiencing anxiety.
What are the potential benefits of L-theanine?
Research on L-theanine shows promise but remains in the preliminary stages. “The research is limited, the sample sizes are small, and the results can vary,” says Crystal Haskell-Ramsay from Northumbria University, UK.
Nonetheless, findings from minor trials indicate that L-theanine may help reduce blood pressure during attention-demanding tasks, and during stressful periods, it might mitigate heart rate surges associated with cortisol, the stress hormone. Some evidence also points to its potential for enhancing relaxation and concentration.
How does L-theanine influence the brain?
Upon entering the bloodstream through the intestine, L-theanine is capable of crossing the blood-brain barrier. It shares similarities with brain glutamic acid and GABA, neurotransmitters responsible for regulating signals in the brain. Studies on rodents suggest that L-theanine may elevate levels of dopamine and serotonin, chemicals linked to various cognitive functions, including mood and reward.
Furthermore, L-theanine is known to increase alpha brain wave activity, which is associated with a calm yet alert state. “When you close your eyes, alpha waves increase instantly,” remarks Manuel Gomez Ramirez from Rochester University in New York.
Does it contribute positively to mood and well-being?
Generally, heightened alpha brain wave activity can enable better focus and diminish distractions, and L-theanine may amplify this effect. “The greater the alpha activity, the better the brain coordinates its surroundings,” explains Gomez Ramirez. The synergy between caffeine and L-theanine likely enhances this effect.
The influence of L-theanine on alpha waves appears to be more pronounced in individuals who are already experiencing anxiety. Studies on stressed rodents reveal that L-theanine can affect dopamine and serotonin levels in certain brain regions, correlating with a reduction in symptoms akin to depression. However, human studies yield inconsistent results, with some indicating a lack of efficacy for generalized anxiety disorder, while others report reductions in stress and anxiety levels.
If L-theanine alleviates anxiety, this could elucidate its benefits for sleep. A review found that it may help individuals fall asleep more swiftly and enhance their overall sleep quality.
Is there sufficient L-theanine in tea?
Teas, particularly green varieties like matcha, contain varying amounts of L-theanine, averaging between 5-40mg per cup. While this could provide a mild effect, most research studies utilize dosages around 200 mg, akin to those commonly found in supplements.
How robust is the evidence for L-theanine?
Many studies involve small participants, focus on short-term outcomes, and frequently test just single doses or limited supplementation periods. “There’s certainly potential, but further work is required in this area,” states Amanda Bluman from the University of Canberra in Australia.
A noteworthy complication is that L-theanine is often studied in conjunction with other components, which complicates the interpretation of results. “It’s challenging to ascertain whether L-theanine is solely responsible,” mentions Haskell-Ramsay. “Disentangling which elements are effective is problematic.”
Moreover, Haskell-Ramsay cautions, “Many people take it consistently for long durations, so long-term data is lacking.”
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Source: www.newscientist.com
