L-theanine 2017-03-13T10:37:45+00:00



L-theanineAlso known as Gamma-ethylamino-L-glutamic acid, L-theanine is a non-essential amino acid found in plants and fungi. Classed as a non-dietary amino acid, theanine is similar to glutamine in structure and its products; glutamate and GABA.

The most common dietary source of L-theanine is tea. Green tea is particularly rich in theanine.

L-theanine and relaxation

One of the most common uses for this amino acid is to decrease stress and anxiety. Most research assessing the effects of theanine on neurological function has been animal based. These studies have found that theanine can affect the serotonin and dopamine levels in the brain, creating anxiolytic effect1, 2.

L-theanineHuman based studies have identified elevated alpha brain wave activity and associated alertness following administration of this amino acid3, 4. Essentially, theanine is a compound that stimulates relaxation but without sedation.

A Japanese study found that college students experienced less anxiety after oral doses of L-theanine5. Also, those participants prescribed this amino acid had less elevated blood pressure after exposure to physical or psychological stress compared with those taking the placebo.

Another Japanese study reported similar findings. In this research, graduate students receiving theanine supplementation responded more favourably under stressful conditions compared with those student taking a placebo 6.

Canadian scientists found that theanine administration could help to reduce the severity of some sleep disorders in boys with attention-deficit hyperactivity disorder (ADHD)7. L-theanine may also have a positive role in anti-psychotic treatments for patients suffering from schizophrenia8.

It is important to note that the above mentioned human studies have been short-term and with a small participant base. While the results are positive, more research is necessary. Larger, long-term studies without methodological weaknesses will help to provide a better insight into the potential anti-stress and anxiety affects of theanine.

L-theanine and cardiovascular health

L-theanineElevated blood pressure and heart beat are not good signs for cardiovascular health. People these symptoms are at an increase risk of heart failure, heart attack, stroke and coronary artery disease.

It is well known that stress can increase blood pressure. In response to stress the nervous system releases high concentrations of vasoconstricting hormones that elevate blood pressure9, 10.

The anti-stress effects of L-theanine on the autonomic nervous system may therefore help to decrease blood pressure. Animals studies have shown that hypertensive rats respond positively to theanine supplementation, successfully reducing blood pressure11, 12.

Other studies have shown that theanine can help to reduce elevated heart rates in humans13, 14, further supporting better cardiovascular health.

Research shows that L-theanine can increase nitric oxide production in endothelial cells15. This improves blood flow throughout the body and is important for reducing the risk of stroke. With healthy blood circulation, the risk of a sudden blood clot (ischemia) is significantly reduced.

L-theanine supplementation may help to improve cardiovascular health by supporting health blood pressure, heath rate and blood flow. Therefore, this amino acid could have a role to play in reducing the risk of heart disease, stroke and heart attacks.

Recommended dosage of L-theanine

L-theaninePeople who drink tea regularly, especially green tea, will have L-theanine in their diet. Generally, a typical cup of black tea will have around 6 mg of theanine. A cup of green tea will have around 8 mg of this amino acid.

Studies report an anti-anxiety effect after single doses of L-theanine of between 200 to 250 mg per day. However, drinking 30 plus cups of tea daily is not recommended! Anyone considering increasing their theanine intake should do so using a quality supplement. It’s important not to exceed 1200 mg per day.


The amino acid L-theanine is found in tea. Many studies indicate that this compound can reduce anxiety. It does this by blocking the brains’ glutamate receptors and stimulating the production of the relaxing neurotransmitter GABA.

Unlike prescription anti-anxiety drugs, this amino acid can reduce stress without impairing motor behaviour or inducing drowsiness.  Instead, L-theanine seems to enhance alertness and improves attention.

In addition to reducing anxiety, there is growing interest in the use of L-theanine to improve cognitive function and cardiovascular health. However, more studies are necessary.

It’s important not to supplement with L-theanine without medical approval. There may be underlying health issues that could lead to adverse reactions, such as hypotension (low blood pressure) for example. Always consult with your doctor before considering taking L-theanine as a supplement.


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