L-Theanine May Help Reduce Effects of Stress

L-theanine is an amino acid found primarily in green and black tea and some mushrooms. A recent study has found that a single dose of l-theanine may help reduce the effects of stress during a stressful situation.

They were given 200 mg of l-theanine or a placebo immediately before performing a stress inducing mental arithmetic task. An EEG test was administered before and after the arithmetic task to measure brainwave activity. Blood pressure, heart rate, self-reported stress, and salivary cortisol levels were evaluated before and after the arithmetic task.

Participants in the l-theanine group saw significantly greater increases in frontal region brainwave alpha power compared to the placebo group. Increases in brainwave alpha power are associated with relaxation. They also saw significant decreases in salivary cortisol levels one hour after completing the test, compared to the placebo group.

The study was conducted by researchers from KGK Science Inc. It was published online ahead of print on September 25, 2021, in the journal Neurological Research.