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All About L-Theanine

Learn all about L-theanine in tea from Sips by

Do you reach for a warm cup of tea to help you feel calm and relaxed, boost your sleep quality, or feel focused and attentive? The myriad of benefits gained from tea is often attributed to L-theanine, the rare amino acid found almost exclusively in tea leaves.

Learn all about the benefits of L-theanine to discover the mood and wellness magic brewing in your favorite cup of tea.

Sips by is a personalized tea discovery subscription. Each month, we match tea drinkers across the U.S. with delicious teas from over 150 global tea brands that we’re sure they’ll love. Members receive 4 teas chosen just for them in every box. Learn more about our tea subscription service.

What Is L-Theanine?

Though tea has been consumed for thousands of years, L-theanine was only discovered as a constituent of tea by scientists in Kyoto in 1949. L-theanine is a rare amino acid found in Camellia sinensis tea leaves and trace amounts in certain types of mushrooms.

Amino acids are usually considered the building blocks of proteins, but L-theanine in tea is a “free-form” non-protein amino acid that does not require digestion. Because L-theanine isn’t bound to a protein, it absorbs into the blood system to the brain — crossing the blood-brain barrier — within 30 minutes of consumption for fast-acting and impactful effects on your body!

Benefits of L-Theanine in Tea

Tea contains powerful catechins, polyphenols, flavonoids, and other healthy compounds that boost the antioxidant and anti-inflammatory benefits of tea. In particular, L-theanine accounts for up to 3% of the dry weight of tea and produces a noticeable wellness boost on the body. Many human and animal studies have shown that the consumption of tea with L-theanine increases the brain’s alpha waves and boosts GABA levels in the brain, which is a calming neurotransmitter. This accumulative effect produced by drinking tea leads to feelings of calm, reduced stress, and increased mental clarity, even when under stress or giving cognitive attention to a difficult task.

The benefits of L-theanine parallel the effects of exercise or meditation — making a cup of tea a great meditative and wellness aid! Many people drink tea with L-theanine to help reduce anxiety, help with insomnia, and boost their immune system. Plus, though more research needs to be done on the health benefits of tea, recent studies indicate that L-theanine shows promising results for contributing to the longevity of brain health.

In addition to the abundance of wellness and mood benefits, L-theanine also gives green tea its unique and enticing “umami” taste.

Do All Types of Tea Have L-Theanine?

Nearly all types of tea made from the Camellia sinensis tea plant contain some level of L-theanine, though certain types of tea will be more impactful than others.

For the highest amount of L-theanine in your cup, green tea is the way to go. Studies also show that black tea is a common runner-up with slightly lower levels of L-theanine.

Notably, pu-erh is the only type of true tea that contains practically zero L-theanine, though it has its own significant health benefits. Herbal teas, such as chamomile or rooibos, do not contain L-theanine as they are crafted with a mix of botanicals instead of the caffeinated tea plant.

L-Theanine and Caffeine

L-theanine and caffeine is proof that opposites do attract. Typically, caffeine is known to energize while L-theanine calms. So how do these two work together to create an amazing mood-enhancing effect?

Research shows that with just 1-2 cups of tea, the L-theanine present cancels out any negative effects from caffeine while enhancing the positive benefits. Instead of becoming jittery, unable to focus, experiencing a caffeine crash, or having trouble falling asleep, the synergy between L-theanine and caffeine leads to a healthy dose of sustained energy.

This dual function means your cup of tea is still a naturally energizing pick-me-up in a good way, with increased mental clarity and focus. L-theanine also increases brain serotonin and dopamine for reduced stress levels, feelings of calm and relaxation, and a boost of productivity.

When to Drink Tea with L-Theanine

Researchers observed students who were asked to solve a set of difficult problems to compare the stress levels of those who consumed L-theanine before completing the problems to those who did not. These studies revealed that L-theanine significantly reduced the stress levels of the students who worked on the complicated problem sets, compared to the students who did not consume L-theanine.

These maximum benefits are believed to occur when you consume approximately 100 mg of L-theanine, which translates to around 4-5 cups of green tea. L-theanine wellness supplements are commonly available, however studies consistently show that the L-theanine in tea is more powerful than L-theanine taken alone.

We recommend drinking a cup of green tea for a powerful work, learning, or study aid. Consuming tea with L-theanine is proven to boost productivity, focus, and reduce stress. The synergy between L-theanine and caffeine sharpens the mind, but also leaves you feeling calm and focused without becoming drowsy.

* These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

Best Green Tea

Discover the best green teas as rated by Sips by's tea-loving Members. From loose leaf green tea to bagged green tea, flavored green tea to unflavored green tea, these are the best green teas from different tea brands around the world. Find your favorite green tea, from matcha to sencha and from pure to flavored, with the caffeine you need to jump start your day. No matter the type of green tea you're searching for, Sips by has options you'll love, whether you love the health benefits of green tea or just love the taste. Discover your new favorite green tea from the best green tea brands today!

Best Green Tea Shop at Sips by


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About Sips by: We’re a female-founded and led startup that makes discovering tea fun, personalized, and affordable. The Sips by Box is the only multi-brand, personalized tea subscription box. Each month, we match tea drinkers across the U.S. with delicious teas from over 150 global tea brands that we’re sure they’ll love. Based out of Austin, Texas, we are adept at savoring a hot mug even when it’s seasonally inappropriate. 

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