L-theanine supports stress and cognitive function in healthy population, says recent study


A clinical trial recently published in Nutrients studied the effects of L-theanine on stress related symptoms and cognitive function in a healthy adult population. 


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A clinical trial recently published in Nutrients studied the effects of L-theanine (Suntheanine from Taiyo International, Minneapolis, MN) on stress related symptoms and cognitive function in a healthy adult population. In the study, researchers randomized 30 subjects to receive either 200 mg per day of L-theanine or placebo for four weeks. Self-rating Depression Scale, State-Trait Anxiety Inventory-trait, and Pittsburgh Sleep Quality Index (PSQI) scores were used to assess stress-related symptoms at baseline and after four weeks of administration. Results showed that scores in all these measures decreased following supplementation with L-theanine. PSQI subscales of sleep latency, sleep disturbances, and use of sleep medication also decreased after L-theanine supplementation.

Measure of cognitive function, specifically verbal fluency, and executive function also improved for subjects taking L-theanine, compared to placebo. “Not only is this one of the first studies to look at how Suntheanine effects stress in a healthy population, it also uses science to confirm the experiential anecdotes we’ve heard over the years,” said Derek Timm, functional ingredient technology expert for Taiyo, in a press release. “We know that Suntheanine stimulates activity in the brain known as alpha waves, which are associated with a relaxed but alert mental state. It is quite likely that this calming alpha wave action is what leads to these improvements.”



1. Hidese S et al. “Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial.” Nutrients, vol. 11, no. 10 (2019): 2362

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