L-Theanine in Tea: Benefits, Where to Find It, and How It Works

Updated: April 27, 2026

L-theanine is an amino acid found naturally in the leaves of the Camellia sinensis plant, the same plant used to make green and black tea. Research suggests L-theanine may help support relaxation, focus, and mood. Every Bigelow green and black tea contains L-theanine naturally, and two Bigelow Signature blends, Peak Energy Black Tea plus Extra L-Theanine and Caffeine and Whispering Wildflowers Herbal Tea plus L-Theanine, contain 25 mg of added l-theanine per 8 oz. cup.

Key takeaways

• L-theanine is an amino acid found naturally in green and black tea leaves.
• Research links L-theanine to relaxation, focus, mood support, and lower cortisol after stress.
• L-theanine paired with caffeine in tea may support steady alertness without coffee-style jitters.
• Bigelow Peak Energy Black Tea and Whispering Wildflowers Herbal Tea each contain 25 mg of added L-theanine per 8 oz. cup.
• Brew green tea with water just below boiling; black and herbal teas with a rolling boil; cover the cup while it steeps.

If you enjoy drinking green and black tea, and Bigelow Tea family, we know you do, then you are also taking in the benefits of L-theanine. Let’s dive in and learn more.

Which teas have L-Theanine? 

L-theanine is an amino acid that is found naturally in Camellia sinensis tea leaves which means that either a cup of black or green tea you drink will contain some amount. If you want to increase your intake, however, some teas are richer in L-theanine than others. For example, green teas are higher in L-theanine overall.

Bigelow Tea also offers two blends in its Signature line with L-theanine added. Peak Energy Black Tea plus Extra L-Theanine and Caffeine is a bold black tea with 25 mg of L-theanine and 75 mg of caffeine per 8 oz. cup, formulated for steady energy and focus. Whispering Wildflowers Herbal Tea plus L-Theanine is a caffeine-free blend of lavender, rose, passionflower, and butterfly pea flower with 25 mg of L-theanine per 8 oz. cup. Because L-theanine is not naturally present in herbal tea, it has been added to this blend to complement the calming botanicals.

How does L-Theanine Work?

Now that you know where to find L-theanine, let’s talk about how it affects your body. As mentioned, L-theanine is an amino acid. An amino acid, notes a study in MedlinePlus, is what is left once the body digests proteins. They help the body grow, repair body tissue and are a source of energy to name only a few of its functions.  A 2020 study, published in Plant Foods for Human Nutrition, suggests that the L-theanine found in tea leaves has a calming effect on the body which helps to reduce anxiety and stress symptoms.  More specifically in a 2021 study published in the Journal of Medicinal Food, L-theanine was shown to improve brain functions by:

• Boosting mood
• Supporting normal sleep
• Helping to manage stress disorders

A 2016 study published in Nutrients reports that participants who consumed 200 milligrams of L-theanine daily, roughly the amount in eight cups of tea, showed lower levels of the stress hormone cortisol and reported feeling more relaxed after stressful tasks compared to those who took a placebo.

In addition to its calming effects, research in that same study in the Journal of Medicinal Food suggests that L-theanine may also improve cognitive performance and protect against age-related cognitive decline. It also cites studies reporting that the caffeine and L-theanine in green tea have synergistic effects on cognition and mood which allows for the same mental alertness one gets from the caffeine in coffee, for example, but without the jitters.

How does L-theanine pair with caffeine in tea?

A 2017 review published in the Asian Pacific Journal of Tropical Biomedicine notes that on its own, L-theanine is associated with relaxation and stress relief. When paired with caffeine, the same compound may help support attention and alertness without the jitters often associated with coffee. For more on this pairing, see Bigelow Tea's blog How Do Caffeine And L-Theanine Make A Perfect Cup Of Bigelow Tea?

How do you brew Bigelow tea?

Bigelow Tea recommends starting with one tea bag per cup, or four to six tea bags per teapot. Use fresh, cold water and let the tap run for about 30 seconds first to aerate it. For green tea, heat the water to just below boiling. For black and herbal teas, bring the water to a rolling boil. Pour the water over the tea bag, cover the cup while it steeps, and follow the steep time printed on the box: generally three minutes for green tea, two to four minutes for black tea, and four minutes for herbal tea. For the full step-by-step, see Bigelow Tea's How to Make the Perfect Cup of Bigelow Tea.

Cindi Bigelow on L-theanine teas

“Tea has always been a source of comfort and well-being. These teas featuring L-theanine provide not only uncompromising exceptional flavor our consumers have grown to rely on, but also include ingredients and nutrients with functional benefits that help support a healthy lifestyle. Enjoy each beautiful cup of tea.” — Cindi Bigelow, third-generation president and CEO of family and woman-owned Bigelow Tea.

Frequently asked questions about L-theanine in tea

What is L-theanine?

L-theanine is an amino acid found naturally in the leaves of the Camellia sinensis plant, the same plant used to make green and black tea. It is studied for its association with relaxation, focus, and mood support.

Which Bigelow teas contain L-theanine?

All Bigelow green and black teas naturally contain L-theanine because they are made from Camellia sinensis leaves. Two Bigelow blends in the Signature line have L-theanine added at 25 mg per 8 oz. cup: Peak Energy Black Tea plus Extra L-Theanine and Caffeine, and Whispering Wildflowers Herbal Tea plus L-Theanine.

Does herbal tea contain L-theanine?

Not naturally. Herbal teas are made from herbs, flowers, fruits, and spices rather than tea leaves, so L-theanine is not naturally present. Bigelow Tea has added L-theanine to Whispering Wildflowers Herbal Tea so it can be enjoyed in a caffeine-free blend.

Does L-theanine make you sleepy?

L-theanine is generally associated with calm and relaxation rather than drowsiness. The 2021 Journal of Medicinal Food review referenced above noted associations with mood, normal sleep, and stress management. Many people drink teas with L-theanine to wind down in the evening or to support a calmer, more focused state during the day.

Next time you feel stressed or anxious, reach for a cup of Bigelow Tea's line of black teas and green teas. The L-theanine each contain may help calm your nerves while sharpening your focus and concentration levels which is one more reason to enjoy another delicious cup.

Ready to find your cup? Browse the Bigelow Green Tea and Black Tea collections, or try Peak Energy or Whispering Wildflowers for a Signature blend with L-theanine added.

The materials referenced on this website, including those related to health information, are provided for informational and educational purposes only. Bigelow is not responsible for and does not endorse content contained in third-party studies or materials. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. You should always consult your medical care provider with respect to any symptoms or medical condition.