What Is L-theanine, and Why Is It Such an Amazing Nootropic?

Photo by Mike Kenneally on Unsplash

L-theanine is an amino acid primarily found in tea. L-theanine’s unique benefits are mainly known for its place in the argument against coffee. Coffee is absent of L-theanine, and tea drinkers herald the superiority of their beverage of choice because of this crucial ingredient.

L-theanine’s supposed benefits are alleviating anxiety and stress and improving memory and focus.

L-theanine is often considered a nootropic, a class of substances categorized by biohackers as “brain boosters” or “smart drugs.” However, you should note that L-theanine’s isolated form predominantly appears as a supplement, not a drug.

This distinction is important because the FDA does not regulate the purported benefits of supplements, murking the waters if L-theanine in supplement form is legitimately effective in cognitive performance.

I’ll go through the fundamental questions of L-theanine, its relationship to coffee, and my recommendation for different L-theanine products.

L-theanine has hidden benefits.

Japanese scientists in 1949 first discovered L-theanine after studying the molecular compounds that make green tea.

A review in Natural Product Communications accounts how the studies behind L-theanine initially came from its relation to food science. Researchers attributed the “umami” flavor of green tea specifically to L-theanine.

It even cuts through the bitterness of some foods like a bar of rich dark chocolate.

But the main benefit that L-theanine offers is its ability to alleviate stress and anxiety.

How does L-theanine work?

In part, the L-theanine’s anxiety relief benefits are because it bears a striking molecular resemblance to the brain-signaling chemical glutamate.

Glutamate is an amino acid that bears the role of a neurotransmitter in the brain. It’s called the “excitatory” neurotransmitter, and too much of it in the brain can cause anxiety.

L-theanine blocks these neurotransmitters, calming these “excitatory” molecules like a school disciplinarian.

It also has a stimulating function, increasing your body’s production of the relaxing neurotransmitter GABA.

How do you know L-theanine improves relaxation?

Mapping out L-theanine’s molecular mechanisms is one thing, but how did science connect these mechanisms to the benefit of anxiety relief?

Qualitative data based on anecdotes can only go so far and aren’t necessarily accepted as “strong science” in the most pejorative sense.

Like with any scientific process, you need to look for measurable markers. For example, you can’t tell someone has caught a cold until they start sneezing. In this case, a way to actively measure whether a person is “feeling” relaxed from a more quantitative perspective is to measure brain waves.

There are five brain waves: gamma, beta, alpha, theta, and delta.

These waves originated from several studies on the brain using an EEG (electroencephalogram) monitor — a device that detects electrical activity using small electrodes attached to your head.

And each has been associated with a specific state of mind. Tea in Health and Disease Prevention illustrates these brain states in the figure provided below:

Out of the five types of brain waves, L-theanine is purported to stimulate alpha brain wave activity, most commonly associated with a state of relaxation and calmness.

The Asia Pacific Journal of Clinical Nutrition conducted a study with 16 participants using L-theanine as a therapeutic intervention and monitoring brain wave activity using an EEG monitor. The figure below illustrates their findings of alpha wave activity between control subjects and subjects who received an L-theanine supplement solution.

As the figure shows, L-theanine’s effects are relatively immediate. After 45 minutes, the EEG monitor already shows alpha brain wave activity — a boon for those partial to quick solutions and wonder how quickly L-theanine affects the brain.

L-theanine and caffeine make the best couple.

We all know coffee for its immense benefits in focus and productivity. It’s a jolt of energy — a bold flavor of alertness in a cup. But drinking too much of it gives you jittery symptoms that might make your hair vibrate off your skin. Aside from the physical symptoms, it can raise your anxiety — especially if you’re already a particularly sensitive individual.

But coffee with a side of L-theanine makes for the perfect concoction — providing coffee’s productivity bang with the calmness of L-theanine. As a result, you get fewer jitters.

You would think that they would react as opposites of each other, but studies show that this combination can improve cognitive ability in both focus and performance.

For example, a study published in Nutritional Neuroscience shows subjects given a combination of caffeine and L-theanine improved both in speed and accuracy with an attention-switching task compared to a group who only received caffeine.

Why don’t you drink tea for the perfect blend of caffeine and L-theanine?

Tea has both caffeine and L-theanine. So why not just drink tea instead of combining a cup of coffee with an L-theanine supplement?

That’s a good question, and it's often the basis of why tea drinkers uphold their drink of choice over their coffee brethren. But many coffee drinkers who are reluctant to make the switch typically claim at least two reasons for their hesitancy:

1. Tea just doesn’t “hit” you hard enough. Coffee is like an electrifying shot, while tea feels like a slow burn.
2. Tea makes you feel nauseous.

These reasons can be attributed to one crucial difference in tea’s composition compared to coffee: The concentration of tannins!

Tannins are a group of astringent compounds called polyphenols. It’s a natural defense mechanism plants have developed to deter animals from eating a plant’s fruit or seed before they are ripe.

A study published in the Journal of Applied Toxicology reveals that over-the-counter Indian tea has twice the number of tannins as roasted coffee beans.

The high amount of tannins in tea actually slows your body’s absorption of caffeine, hence why you don’t get the immediate spark that coffee brings you.

The high concentration of tannins, especially if consumed on an empty stomach, can also cause nausea. Of course, tea drinkers will tell you that a splash of milk or some breakfast can help alleviate nausea. But if you’re practicing intermittent fasting, a splash of milk might not be an option for you.

L-theanine in supplement form is not the same.

The early Japanese scientists found it difficult to isolate and stabilize L-theanine from green tea. The review in Nature Product Communications, mentioned earlier, provides a record of the failed attempts to separate L-Theanine from tea leaves in its pure form.

Once synthetic options were considered, after much trial and error, The Taiyo Kagaku Company patented the first synthetic form of L-theanine. This form is also known as Suntheanine®.

It’s essential to consider Suntheanine® when shopping for L-theanine products. I’ll explain why.

L-theanine has a mysterious trouble-making cousin, D-theanine.

Technically, theanine comes in two forms: L-theanine and D-theanine. However, no one ever really talks about D-theanine because no one really knows much about it. L-theanine gets most of the attention because it’s the most commonly studied form of theanine today.

According to NutraIngredients, preclinical research from Iowa University suggests that D-theanine may actually inhibit the absorption of L-theanine.

Also, NutraIngredients reports that the study reveals glaring mismatches in supplement labels and the bioavailability of L-theanine in three commercially-available products.

Dr. Daniel Armstrong, the principal researcher of the study, denotes,

“What poses a potential concern to the consumer is the safety and efficacy of theanine racemates sold as L-theanine, as this is a complete unknown.”

Armstrong reveals that several commercially-available products he tested claim to contain L-theanine but actually contain a significant amount of D-theanine.

Is Suntheanine® the most superior form of L-theanine?

Tea is always an excellent source of L-theanine, but its concentrations are often small. A study published in Food Chemistry details black teas containing approximately 24mg/200ml of L-theanine while green tea provides 8mg/200ml.

That’s quite a disparity between the sizes listed on L-theanine supplements, which typically range from 100–200mg per serving. If you do the math, a 200mg supplement of L-theanine is the equivalent of about 8 cups of black tea or 25 cups of green tea.

That’s a lot of tea, even for an Englishman. Is that really good for you?

The FDA seemed to generally feel good about some products. They issued a GRAS (generally recognized as safe) designation for Suntheanine®, the patented synthetic form of L-theanine produced by Taiyo International.

Suntheanine® also appears to have several clinical studies showing positive toxicology studies as reported by l-theanine.com. However, it should be noted that l-theanine.com is a property owned by NutriScience Innovations, a company that includes Suntheanine® as part of its exclusive portfolio of proprietary ingredients.

Also, a sweep through clinicaltrials.gov only appears to show Suntheanine® mentioned by name once, via a study published in Alternative Medicine Review. But it’s encouraging that the study conducted a randomized, double-blind, placebo-controlled trial — the gold standard of scientific research.

Suntheanine® also received LGC’s Informed Ingredient certification. It’s always good to see a supplement brand seek independent verification from third parties (since the FDA doesn’t regulate supplements in the same way as drugs).

Still, LGC’s certification program is relatively new (launched in 2021), lacking the reputably of more established certifications from organizations like NSF International, USP, or Consumer Lab.

What about AlphaWave®?

There’s another recently patented form of L-theanine called AlphaWave® that’s created by Ethical Naturals. According to Bevnet, AlphaWave® uses a different proprietary process to derive its L-theanine than Suntheanine®.

Launched around 2010, AlphaWave® also has one randomized, double-blind, placebo-controlled study. It also appears to have received GRAS designation by the FDA, and its facilities are certified by NSF International.

However, the ingredient doesn’t appear to be widely used as Suntheanine®. Ethical Naturals appear to be the only way to get your hands on AlphaWave®, but they make you fill out this strange order form.

Whereas Suntheanine® is widely used in various products, it doesn’t seem like AlphaWave® has any penetration in the consumer market.

How do you know which supplement brand to choose if you want to take L-theanine?

You can make quick decisions on which supplements to trust just by looking at the label. For L-theanine supplements, look for the following:

1. Make sure it contains Suntheanine®. Suntheanine® is the purest synthetic form of L-theanine that is commercially available. It also has actual human clinical science behind it. If it just says L-theanine and not Suntheanine® with its registered mark, it’s probably not a reliable form of L-theanine.
2. Look for any mention that the product is cGMP certified. cGMP refers to the Current Good Manufacturing Practice regulations enforced by the FDA.
3. Look for anything that says it’s third-party verified. USP, NSF International, and ConsumerLab are the most reputable.

Here’s a quick review of some of the most popular supplement brands that contain L-theanine (Please note I do not earn a commission for any of these products):

Integrative Therapeutics

• Price: Moderate
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? Their quality page says so, but the absence of the cGMP seal on the label possibly indicates that their L-theanine supplement is not manufactured at a cGMP facility.
• Is the product third-party verified? Their quality page says they are NSF Certified®, and it looks like they are listed on NSF’s database. But the absence of the signature NSF seal on the label possibly indicates that only some of their products can bear the mark.
• Trustworthiness: Low. Maybe their other products are better, but their L-theanine line doesn’t look convincing.

Sport’s Research

• Price: Cheap
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? Yes, and it’s on the label as well.
• Is the product third-party verified? They say it’s third-party quality tested, but they don’t mention who did it. Given the price and vagueness, it’s likely not a reputable third party.
• Trustworthiness: Moderate. I wish they had better third-party verification, but the price is unbeatable for the quality.

Thorne

• Price: Expensive
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? Their quality page says their products are CGMP certified, but the absence of the cGMP seal on the label possibly indicates that their L-theanine supplement is not manufactured at a cGMP facility.
• Is the product third-party verified? Their quality page says they are NSF Certified®, and it looks like they are listed on NSF’s database. But the absence of the signature NSF seal on the label possibly indicates that only some of their products can bear the mark.
• Trustworthiness: Low. It’s one of the most expensive products on the list, and the absence of cGMP and third-party verification label makes at this price point makes it one of the worst.

Double Wood

• Price: Cheap
• Does the product contain Suntheanine®? No, it has a non-descript form of L-theanine.
• Is the product cGMP certified? Their product page says so, but there’s no seal on the label.
• Is the product third-party verified? They have a verification test result pdf on their product page, but it’s from a smaller, non-reputable lab called Micro Quality Labs.
• Trustworthiness: Low. The bottle has no patented ingredients, no cGMP label, and the third-party verification lab is not a reputable name.

Doctor’s Best

• Price: Cheap
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? No.
• Is the product third-party verified? No, but it seems like they do their own testing.
• Trustworthiness: Low. No cGMP label and no third-party verification.

Now Supplements

• Price: Cheap
• Does the product contain Suntheanine®? No, it has a non-descript form of L-theanine.
• Is the product cGMP certified? Yes.
• Is the product third-party verified? No, but their other products seem to be tested.
• Trustworthiness: Low. No patented ingredients and no third-party verification.

Nature’s Trove

• Price: Really Cheap
• Does the product contain Suntheanine®? No, it has a non-descript form of L-theanine.
• Is the product cGMP certified? Yes.
• Is the product third-party verified? No.
• Trustworthiness: Low. No patented ingredients and no third-party verification.

Pure Encapsulations

• Price: Really Expensive
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? No.
• Is the product third-party verified? No, but they do their own testing.
• Trustworthiness: Low. No cGMP certification or third-party testing.

Klaire Labs

• Price: Moderate
• Does the product contain Suntheanine®? Yes, it has Suntheanine®.
• Is the product cGMP certified? Yes, there’s no seal, but there is mention of it on the label.
• Is the product third-party verified? No, but they do their own testing.
• Trustworthiness: Moderate. I wish they had better third-party verification, but it fits the bill for the price.

With the few brands I’ve extensively reviewed, it’s clear that L-theanine is not a high-priority ingredient for many of these brands. Most of them only check one of the three boxes I measured in my criteria. The three criteria were (1) the existence of Suntheanine®, (2) a cGMP label, (3) and a legitimate third-party verification.

Klaire Labs and Sport’s Research at least get two out of three marks. If you’re going to try out L-theanine for yourself, Klaire Labs and Sport’s Research appear to be safer bets based on my shortlist analysis.

Should you take a green tea extract instead of an L-theanine supplement?

Matcha.com seems to think so, but they obviously have a commercial agenda to tell that story since they sell green tea extract products.

Green tea extract sellers and their allies push the natural product agenda in their argument against L-theanine supplements because L-theanine supplements are largely synthetic.

But there hasn’t been a direct toe-to-toe study to compare green tea extracts and L-theanine in the scientific literature, so it’s hard to tell which one is better.

However, a study published in the Journal of Medicinal Food shows positive preclinical data when combining the two ingredients.

Just start with green tea steeped a little longer than usual.

The not-so-transparent supplement market makes synthetic forms of L-theanine tough to trust without any clear markings of verification and patents on their labels. Some of them are also quite expensive.

However, the simplest and probably cheapest way to try out L-theanine is to steep your tea longer than usual. The longer the steep, the more L-theanine is extracted from the tea leaves.

Research published in the Journal of Separation Science lists several factors to optimize L-theanine extraction from tea. According to the article, the optimal conditions for green tea are as follows:

• 80℃ water temperature
• 30 minutes of brew time
• 20:1 mL/g water-to-tea ratio
• A tea particle size of 0.5–1mm

The Biohacker’s Journal recommendation:

Synthetic forms aren’t always perfect, and in some cases, the natural way of doing things might be the best way to enhance your productivity. It may not be the sexiest biotech out there, but it’s hard to beat an ingredient that’s been around human existence for thousands of years.

From my experience, L-theanine supplements were largely ineffective. I benefited from drinking teas with lighter tannins like green tea and oolong tea. Indian tea variations gave me the most symptoms, such as stomach aches and nausea, but that was because I’m intermittent fasting, and I was drinking tea on an empty stomach.

But it’s only been about two decades since Suntheanine® hit the market, so I’m still optimistic about synthetic options. As research continues to build, L-theanine synthetics will only get better. AlphaWave® has already built upon the existing science. I only hope that supplement companies dedicate the resources to ensure the quality control we deserve.