What Are the Benefits of Using L-Theanine?

Green tea is a rich dietary source of L-theanine.
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L-theanine, an amino acid you get from green tea, is also found in black tea and in small amounts in mushrooms. If you're having a stressful day, a dose of this amino acid may be just what you need. Whether you take in L-theanine through diet or from nutritional supplements, it may help keep you calm and rested. L-theanine may even benefit your brain function and help you stay alert and focused.

Anxiety Reduction

    Supplement manufacturers commonly market L-theanine as an alternative treatment for anxiety. There may be something to that claim, according to researchers who published a study in "Biological Psychology" in 2007. L-theanine interacts with receptors in your brain, changing the way your body deals with stress. The researchers tested the effects of L-theanine on 12 people and found that it lowered their heart rate during stressful events, indicating that this amino acid may help keep stress levels down.

Improved Sleep

    If you're having trouble sleeping, taking L-theanine may help you get the rest you need, according to authors of a research paper published in "Alternative Medicine Review" in 2012. After giving 400 milligrams of L-theanine to 98 boys with attention-deficit hyperactivity disorder for six weeks, they found that the boys slept more soundly, for longer periods than boys who didn't take L-theanine. Because none of the boys experienced unpleasant side effects from the supplement, the researchers said it may be a safe and effective treatment for sleep disorders.

Brain Function

    Green tea is rich in L-theanine, but its combination of L-theanine and caffeine may benefit your brain, according to researchers who published a study in "Nutritional Neuroscience" in 2010. In the study, 44 young adults took either 97 milligrams of L-theanine and 40 milligrams of caffeine or a placebo before performing a cognitive task. Those who took the L-theanine and caffeine showed much more accuracy and alertness than the placebo group. The researchers concluded that L-theanine and caffeine, taken together, may help people stay focused while doing challenging tasks.


    Although there are no known side effects to taking L-theanine supplements, New York University's Langone Medical Center warns that L-theanine may change the way lipid-lowering medicines, sedatives and chemotherapy work, so you shouldn't take it if you're using any of those medications or treatments. If you're drinking green tea to boost your L-theanine intake, don't go overboard. Drinking more than 5 cups of green tea per day may be unsafe because of its caffeine content, according to Medline Plus.

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