L-theanine is an amino acid primarily found in green tea and even some mushrooms that can reduce cortisol levels in the body, therefore promoting calmness and improving our stress response. L-theanine can also benefit cognitive functioning, which includes improving focus, memory and attention. Alongside being neuroprotective, L-theanine may also help to reduce feelings of anxiety to help improve mood. It also reduces fatigue while reducing the feelings of brain fog, supporting optimal mental performance.
- Memory Loss
- Brain Fog
- High Cortisol
When paired with caffeine, L-theanine may help to reduce feelings of anxiety as well as improve focus and attention. This is why many people describe feeling a calm uplift when consuming green tea over other caffeinated beverages such as coffee. L-theanine also improves alertness and reduces fatigue, while reducing the feelings of brain fog. Another review of recent studies suggests that L-theanine may improve attention, working memory, mental flexibility and even self-control.
A review of clinical trials conducted in humans showed that overall, consuming L-theanine helps to reduce feelings of acute stress and anxiety in people experiencing stressful situations. This has been repeatedly observed both psychologically through measuring self-reported subjective stress, as well as through measuring a change in physiological responses to stress.
The effect of L-theanine consumption on the body’s physical responses has been captured by measuring compounds in the body that increase in events of stress and anxiety. Biomarkers secreted in saliva in response to stress such as cortisol, amongst others, are significantly lower in those consuming L-theanine in comparison to those given a placebo. A lower heart rate as well as blood pressure have also been identified in adults taking L-theanine compared to those not taking L-theanine.
The effect of consuming L-theanine on psychological measures, including stress, anxiety and depression, has been measured in the literature using clinical questionnaires and rating scores. After consumption of L-theanine, feelings of subjective stress and anxiety are significantly reduced. When used alongside sertraline (anti-depressant medication) in individuals with major depressive disorder, individuals even achieved a lower rating score for depression compared to those taking placebo, demonstrating the possible mood-boosting effects of L-theanine.
Furthermore, after four weeks of supplementation with L-theanine, individuals also showed a reduction in sleep disturbances, stress-related functions (including feelings of depression and anxiety) and a significant improvement in cognitive functioning. These findings suggest that it has the potential to support optimal brain health in the general population.
Research and studies
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Journal of Nutrition & Intermediary Metabolism
Theanine consumption, stress and anxiety in human clinical trials: A systematic review
Journal of Medicinal Food
Effects of L-theanine on cognitive function in middle-aged and older subjects: a randomized placebo-controlled study
Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial
Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial
Pharmacology Biochemistry and Behaviour
Anti-stress effect of theanine on students during pharmacy practice: Positive correlation among salivary α-amylase activity, trait anxiety and subjective stress
L-Theanine reduces psychological and physiological stress responses
Journal of psychological anthropology
Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses
Journal of affective disorders
L-theanine adjunct to sertraline for major depressive disorder: A randomized, double-blind, placebo-controlled clinical trial
Plant Foods for Human Nutrition