Benefits of L-Theanine and Green Tea

L-Theanine is an amino acid most commonly found in green tea. It has a similar chemical structure to glutamate, the most common neurotransmitter in the brain, which plays a role in normal brain function, including learning, mood stabilization, and memory.

Studies show that L-Theanine can have similar effects on the brain and many additional benefits.

How it works

Not only does L-Theanine elevate calming brain chemicals, such as serotonin and dopamine, but it also reduces the chemicals that are likely to cause anxiety and stress.

The amino acid also triggers alpha waves in the brain, which linked of relaxation. These three effects can have a significant impact on how a person copes with anxiety and stress.

digital illustration of neurons on brain background

cognitive function

L-Theanine may positively affect cognitive function in healthy adults. A study looked at the effects of four weeks of L-Theanine supplementation on brain function by scoring participants in different categories.

Scores for stress-related symptoms, such as anxiety and depression, decreased, while those for cognitive functioning, such as fluency and problem solving, increased. Study participants with low performance in verbal fluency at baseline saw a remarkable improvement after taking L-Theanine.

intelligent woman solving problems at work


Another study looked at how L-Theanine affected stress levels, and asked participants to complete tasks at baseline and then one hour and three hours after having a drink containing L-Theanine. The results show that not only were stress levels significantly lower after one hour, but the cortisol response was also significantly lower after three hours.
Cortisol is known if the “stress hormone” and helps control blood sugar and blood pressure and affects multiple body systems.

hand spinning cubes to spell Less Stress

Opioid dependence

Between 21 and 29 per cent of people prescribed opioids for chronic pain use other than intended, and between 8 and 12 percent develop an addiction.

One of the reasons people find it difficult to come off opioids is because of withdrawal symptoms, but a study shows that L-Theanine can help. When morphine-addicted monkeys in this study were given L-Theanine, signs of withdrawal — such as pacing, gagging, and fighting — decreased.

doctor holding a handful of prescription pills


L-Theanine may also have sleep benefits. Many drugs used to help sleep problems have unexpected side effects and can lead to dependence or stop working with long-term use.

One study found that when L-Theanine was taken with GABA, another amino acid available as a supplement, both the quality and duration of sleep improved. Interestingly, the combination of L-Theanine and GABA was more effective than either of these supplements alone.

elderly man sleeping in his bed

Blood pressure

A study shows that L-Theanine can also help control blood pressure. This study looked at how L-Theanine and caffeine affect the ability to perform tasks under stress. The results show that L-Theanine inhibited blood pressure rises in study participants whose blood pressure rose more than average after taking the placebo.

These results indicate that L-Theanine not only reduces the feeling of anxiety, but also moderates blood pressure in people prone to a high stress response.

hand with weight during blood pressure test;  healthy concept


L-Theanine is most commonly found in green tea, and a lot studies have looked at the effects of green tea on cancer. Several studies show that drinking tea is associated with a lower risk of lung cancer, breast cancer, esophageal cancer, colon cancer and liver cancer.
Another study showed that L-Theanine can enhance the effects of several chemotherapy agents. More data is needed, but the research suggests that L-Theanine may be effective in preventing or treating cancer.

smiling mother with cancer hugging daughter

Benefits of L-Theanine

In addition to all the reported health benefits, L-Theanine is generally safe to take with you, although the dosage has not been determined. Studies have shown that it is well tolerated and has no serious side effects. It is not addictive and there are no signs of dependence with long-term use.

woman about to drink green tea

Cons of L-Theanine

The biggest drawback of L-Theanine is that: it can interact of some medications and supplements. Some people choose to take L-Theanine supplements instead of drinking green tea. Supplements are not regulated by the FDA, so consumers cannot be sure of the efficacy, safety, or dosage of the one they choose.

supplements on the table

Who Should Avoid L-Theanine?

People who are pregnant, breastfeeding or allergic or sensitive to green tea should prevent taking L-Theanine. It can also interfere with the effects of caffeine or cause blood pressure to drop too much in people taking other medications to control it.

People taking medications or supplements to manage sleep disorders, anxiety, or hypertension should talk to their doctor before taking L-Theanine.

smiling pregnant woman and her partner