L-Theanine

L-theanine is an amino acid that has been proven to enhance both cognitive function and mood in humans. It is primarily found naturally occurring in green tea, as well as in certain types of mushrooms. When consumed orally, it is easily absorbed by the intestinal tract and can pass through the selective blood-brain barrier to promote neuroprotective and neuro-enhancing effects, including improved memory, sleep and stress response.

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.