Theanine is an amino acid (a building block for proteins) found in green tea.
People use theanine for treating anxiety and high blood pressure, for preventing Alzheimer’s disease, and for making cancer drugs more effective.
How does it work?
Theanine has a chemical structure very similar to glutamate, a naturally occurring amino acid in the body that helps transmit nerve impulses in the brain. Some of the effects of Theanine appear to be similar to glutamate, and some effects seem to block glutamate.
Health Benefits of Theanine
1) Theanine Reduces Anxiety and Stress
After participants took L-Theanine, they performed mental tasks. Compared to the patients who took a placebo, they had lower stress symptoms, along with reduced heart rates and blood pressure (R, R2).
Daily supplementation in schizophrenic patients leads to reduced anxiety (R).
It also promoted relaxation in healthy patients (R, R2).
Supplemental doses of theanine that promote relaxation do not cause sedation (R).
In addition, theanine may also have stimulating effects when given at smaller doses, doses that are less than half the doses that promote relaxation (R).
2) Theanine Improves Brain Function
L-Theanine supplementation helps increase attention and improve memory.
In men and women who suffered from minor brain damage, a combination of L-Theanine and green tea extract improved memory during a mental exercise. It did so by increasing delayed recognition during a memory test (R).
The subjects’ attention span and alertness increased during the memory test as well (R).
An improvement in attention has also been noted in healthy people who are prone to anxiety (R).
3) Theanine Reduces Negative Effects of Caffeine and Improves Its Cognitive-Enhancing Effects
Theanine and caffeine are typically found together in tea. A combination of caffeine and theanine together significantly improves alertness, reduce fatigue, and improves task-switching accuracy (R).
High dose caffeine (250 mg, equivalent to 2.5 cups of coffee) has some negative effects, such as jitters and increased blood pressure. Theanine was able to mitigate the increase in blood pressure (R).
L-Theanine decreases the negative and jittery effects of caffeine in rats (R).
However, human studies found that L-Theanine helps reduce caffeine jitters, although the changes were not significant (R, R2).
L-Theanine changes the pharmacological profile of caffeine in humans, as the combination of caffeine and L-Theanine have somewhat different cognitive enhancement effects. (R)
4) Theanine Protects the Heart and Blood Vessels
Theanine improves blood vessel function by increasing nitric oxide production (R, R2).
It also prevents fat peroxidation of LDL (low-density lipoprotein), which reduces the risks of hardening of the arteries (R).
Theanine also decreased blood pressure in hypertensive rats (R, R2).
5) Theanine Is an Antioxidant
The L-Theanine in tea exerts a dose-dependent antioxidant effect (R).
It also restored the antioxidant capability of liver cells, which helps prevent liver injuries (R).
In rats, it dose-dependently decreased oxidative damage and stopped inflammation (R).
6) Theanine Increases Sleep Quality
ADHD may cause sleep disturbances. Boys who took two 200 mg doses of L-Theanine daily for six weeks had a higher quality of sleep compared to ones who took a placebo (R).
They had higher sleep percentages and better sleep efficiency. Supplementation also decreased the amount of time the participants were awake during the night after sleep started (R).
7) Theanine Reduces Symptoms of Schizophrenia
Taking 400 mg daily for eight weeks resulted in less schizophrenic symptoms. The patients reported lower anxiety, less sensory complaints, and fewer muscle problems (R).
8) Theanine May Enhance Th1 Immunity and Combat Stress-Related Weakened Immunity
Theanine may boost the activity of T cells that protect against infection and tumors (R, R2). Theanine shifts the Th1/Th2 balance towards Th1 (R).
The study showed that tea drinkers, when compared to coffee drinkers, had increased production of cytokines by T cells (R).
High cortisol generally suppresses the Th1 immune system and stimulates the Th2 immune system. In the presence of stress, theanine helps to reverse this trend. Theanine decreased suppression of the immune system and inflammation caused by high cortisol from endurance exercise (R, R2).
Theanine may help with allergies. It decreased the production of IgE and histamine release from mast cells (R, R2).
Studies showed that theanine intake prevents the flu and common cold (R, R2, R3).
Theanine intake also alleviates inflammation and promotes recovery after surgery (R, R2).
9) Theanine As an Adjunctive Cancer Treatment
Theanine enhanced anti-tumor effects of cancer-killing drugs (R, R2).
It also reduced the toxicity of these drugs to healthy tissues (R, R2, R3).
Theanine decreased growth and migration of liver and lung cancer cells (R, R2).
10) Theanine May Reduce Symptoms of Depression
In an open-label study, L-Theanine intake for eight weeks helped with depressive symptoms, anxiety, sleep disturbance, and cognitive impairments in patients with major depressive disorder (R).
11) Theanine Helps with Weight Loss
Theanine, along with other components of green tea, reduced triglyceride and fatty acid levels in the blood.The food intake and body weight decreased in the mice given theanine (R).
12) Theanine May Heal Stomach Ulcers
L-Theanine healed stomach ulcers at a dose of 10 mg/kg body weight, but aggravated ulcers at a higher dose of 40 mg/kg body weight (R).
It alleviated the adverse effects of non-steroidal anti-inflammatory drugs as an antioxidant and by stimulating prostaglandin E production(R).
How Does Theanine Work?
Theanine is able to cross the blood-brain barrier and affect the brain directly. In the brain, it targets brain chemicals that regulate arousal, anxiety, pleasure, and attention (R).
When administered to rats in the stomach, theanine is found in the blood after one hour, peaks in the brain at five hours, and is completely eliminated at 24 hours (R).
L-Theanine increases brain serotonin and dopamine levels, with possible improvement in memory and learning (R, R2).
It also increases the levels as well as the effectiveness of GABA, the body’s main inhibitory neurotransmitter (R).
Theanine also increases alpha brain wave activity, which causes mental relaxation, concentration, and deep REM sleep (R, R2, R3).
L-Theanine increases glutathione levels, the body’s most important antioxidant molecule (R).
L-Theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks (R).