Recent studies are indicating an interesting link between stress reduction and a common household item: tea. Tea has long been known as a rich source of flavonoid antioxidants, but its lesser-known therapeutic property is its source of L-theanine, a non-protein amino acid and a natural constituent in tea (2). Research is now showing the potential connection between L-theanine and the reduction of psychological and physical stress, even noting a decrease in ADHD symptoms in school-aged boys (2). How does L-theanine work, and why does it reduce stress symptoms in higher doses?
In a number of preliminary studies, L-theanine has been linked to affecting the brain and its reaction and response to stress positively (2,3). In studies conducted on animals, for example, it was found that L-theanine affected dopamine and serotonin concentrations in the brain and reduced blood pressure in hypertensive rats (3). Constituting about one to two percent of the dry weight of tea, the L-theanine levels in a single serving of tea equals to about 20 milligrams (2). At this rate, one would need to drink upwards of 10 to 15 cups of tea per day to benefit from its potential therapeutic benefits, making a case for higher dosage.
In a study conducted by the Unilever Food and Health Research Institute in the Netherlands, researchers looked at L-theanine’s effect on brain function through electroencephalograph (EEG) testing to show that L-theanine significantly increases activity in the alpha frequency band, which indicates that it relaxes the mind without inducing drowsiness (2). EEG measurements were taken at baseline and at 45, 60, 75, 90 and 105 minutes after healthy participants ingested 50 milligrams of L-theanine and the results were noteworthy: There was a greater increase in alpha activity in the brain across time in participants who ingested L-theanine as opposed to a placebo (2). The rise in alpha activity in the brain indicates heightened mental alertness and attention, making a case for the benefits of L-theanine. (2)
Another study considered L-theanine’s ability to block the binding of L-glutamic acid to glutamate receptors in the brain, which has been linked to reducing stress by inhibiting neuron excitation in the brain (3). Researchers orally administered L-theanine or caffeine to 14 subjects who were put under physical or psychological stress to test their resistance to stressful situations. The results showed that L-theanine was responsible for significantly [inhibiting] the blood pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after a placebo intake (3). Caffeine had a similar, but much smaller, effect on participants, further making the case for L-theanine’s effect on anxiety and stress on a physiological level. (3)
In a study published in 2013 in the journal of Pharmacology, Biochemistry and Behavior, scientists examined the anti-stress effect of L-theanine on fifth year pharmacy students who were randomly administered 200 milligrams of L-theanine or a placebo pill twice a day for one week prior to the pharmacy practice and continuing for 10 days into the practice period (4). Generally thought of as a high-stress group of individuals, the study assessed participant anxiety levels through salivary α-amylase activity (sAA), a marker of sympathetic nervous system activity. By the end of the study, researchers concluded that subjective stress was significantly lower in the L-theanine group than the placebo group, suggesting that it does indeed have an anti-stress effect (4). Furthermore, lowered levels of subjective stress in the L-theanine group determined that theanine intake suppressed initial stress responses of students assigned for long-term commitment of pharmacy practice (4).
L-theanine is also being considered as a therapeutic treatment for young children suffering from attention deficit hyperactivity disorder (ADHD) in relation to its effect on sleep quality. Sleep problems are a common comorbidity associated with ADHD, and disturbed sleep is often linked to exacerbating the disorder (5). The randomized, double blind, placebo-controlled study investigated the efficacy and safety of L-theanine as an aid to improving sleep quality in 98 boys, aged 8-12 years, who had previously been diagnosed with ADHD. Subjects were administered 100 milligram tablets of L-theanine or a placebo twice daily for six weeks and were evaluated for sleep problems for five consecutive nights at baseline and at the end of the six weeks. Surprisingly, the study found that boys who consumed L-theanine obtained significantly higher sleep percentage and sleep efficiency scores, along with a non-significant trend for less activity during sleep, defined as less time awake after sleep onset (5). Not only did the study show improvements in sleep patterns, the relatively high dose of L-theanine that was administered over this time period was well tolerated and didn’t show significant adverse effects (5). This study indicates a plausibly safe method of therapy for young children with ADHD with naturally derived L-theanine. (5)