Suntheanine vs L-Theanine: Is one REALLY better?

Theanine is one of the most effective nootropic supplements in the world. It is a key ingredient in most of the leading brain supplement stacks on the market today. On top of that, practically every high-quality energy supplement and caffeine pill contains a good serving of L-Theanine in one form or another.
Theanine has many benefits relating to cognitive performance, which is why it is found in so many of the best nootropics and caffeine pills on sale today. In particular, ADHD-focused nootropics usually contain lots of Theanine.

But does the kind of Theanine you take make a difference?

More specifically, is there a difference between L-Theanine and Suntheanine?

This is a very good question. You'll see lots of people - especially supplement manufacturers - saying that to really get the benefits of Theanine, you need to use a "superior form" such as Suntheanine. They claim that Suntheanine is better than simple L-Theanine due to its higher purity and greater bioavailability.

But is there any truth to these claims?

Is Suntheanine better than L-Theanine? Is there really any difference between these two forms of Theanine? What is the best Theanine supplement for you to take right now? Does one have more negative side effects than the other?

Let's take a closer look at both of these popular Theanine supplements to see if there really is a difference and - if there is - whether it's worth paying for!

What is L-Theanine?

L-Theanine is simply the most common isomer of the amino acid Theanine. Theanine occurs in two forms: L-Theanine and D-Theanine, with the former being vastly more common in nature.

Theanine is found naturally in large quantities in tea and in certain mushrooms. You may hear that green tea leaves contain much more theanine than black tea, but this isn't true; in fact, black tea and green tea usually contain essentially the same amount of Theanine.

Theanine green tea source

The reason why most of you will know about Theanine is because of its efficacy as a supplement. Theanine supplements (and increasingly Suntheanine supplements) are increasingly being used either by themselves or as part of a nootropic stack. L-Theanine is by far the most widely-used kind of supplement form of Theanine, although an increasing amount of pre-made nootropic supplements are using Suntheanine instead.

Clinical studies have shown beyond doubt that using either L-Theanine or Suntheanine deliver massive and varied cognitive benefits.

Using large doses of either L-Theanine or Suntheanine have been found to be effective for improving:

  • Focus and mental clarity
  • Reaction times and attention
  • Physiological stress responses
  • Sleep quality
  • Mood

These benefits have all been well established by high-quality scientific studies and human clinical trials. 

In one study, researchers found that daily consumption of Theanine reduced the reaction time to attention tasks (Stroop test, Part 1), and it increased the number of correct answers and decreased the number of omission errors in working memory tasks in men and women aged 50-69 (Baba, Yoshitake et al., 2021).

Both L-Theanine and Suntheanine supplements are also known to be extremely effective for reducing the side effects of caffeine. Incredibly, Theanine supplements suppress stimulant side effects while amplifying the benefits.

For example, in a 2008 study, researchers found that a combination of L-Theanine and Caffeine "improved both speed and accuracy of performance of the attention-switching task at 60 min, and reduced susceptibility to distracting information in the memory task at both 60 min and 90 min" (Owen, Gail N et al., 2008). The effects was greater than that observed in people using caffeine alone. 

Because Theanine (as either L-Theanine or Suntheanine) has these benefits, it is being studied as a treatment for symptoms of attention deficit hyperactivity disorder, anxiety disorders and chronic stress syndrome. It has already been found to be an effective natural treatment for insomnia and various sleeping disorder.

So how does Theanine produce these benefits? What is actually going on in the brain when you take L-Theanine or Suntheanine?

What L-Theanine does to your brain

So what is happening in the brain when we take L-Theanine?

L-Theanine works by influencing the activity of certain neurotransmitter receptors in the brain. It also has an effect on neuropeptide levels in the brain, although this effect is responsible for its long-term benefits that have not been fully studied.

First of all, L-Theanine is an antagonist of group 1 metabotropic glutamate receptors. These receptors act as regulators for other neurotransmitter receptors. L-Theanine is structurally similar to glutamate, which is one of the main excitatory neurotransmitters in the human body.

Studies show that L-Theanine easily binds to glutamate receptors. This effectively "blocks" the receptors and prevents glutamate from activating them. Because glutamate excites the CNS, blocking these receptors 'calms' the CNS, reducing nerve activity overall.

There is also some very strong evidence suggesting that L-Theanine boosts levels of GABA, serotonin, and dopamine. Here is a quick overview of what these neurotransmitters do:

  1. GABA is the opposite of glutamate in many ways; it is the main inhibitory neurotransmitter in the human CNS. It works to reduce overall nerve activity
  2. Serotonin increases feelings of joy, euphoria and togetherness. Boosting serotonin levels will increase overall wellbeing and promote a positive mood
  3. Dopamine has a wide range of roles in the human brain and wider nervous system. Its main job is motivating behavior; dopamine produces a rewarding feeling when you work towards a goal

By promoting the release of these neurotransmitters - especially GABA - L-Theanine works to promote quality of sleep, physiological stress responses, symptoms of depressive disorder, mild cognitive impairment, Alpha brain wave activity, and according to some clinical trials, may even help with the symptoms of attention deficit hyperactivity disorder.

Does L-Theanine boost BDNF?

There is some evidence that L-Theanine might boost the production of neuropeptides in the brain, including both Brain Derived Neurotrophic Factor (BDNF) and Nerve Growth Factor (NGF).

Looking at the scientific studies on this, it seems highly likely that large doses of L-Theanine do in fact increase BDNF levels in the brain. Raising BDNF over long periods of time will have tremendous benefits for brain health, cognitive performance and mental health.

What is Suntheanine®?

So what about Suntheanine? What is this supplement and how is it different to L-Theanine?

Suntheanine is simply L-Theanine produced by a particular patented process which involves using microbes to produce the amino acid rather than extracting it from ground up tea leaves. According to the patent filed by the makers of Suntheanine, Taiyokagaku Co. Ltd., their production process is much more efficient since only about 1.5% of tea leaves are theanine while microbes can produce almost pure theanine on an industrial scale.

Suntheanine logo

This has led the makers of some dietary supplements to claim that Suntheanine is more potent than L-Theanine.

But there is ABSOLUTELY NOTHING in the Suntheanine patent to make you think that's the case. Suntheanine is different to L-Theanine only in the production process. The actual product itself is the amino acid L-theanine!

Suntheanine is not a more concentrated form of L-Theanine. It is just that the production process is more efficient. This should in theory make Suntheanine cheaper than L-Theanine, but in reality is is a lot more expensive!

What Suntheanine® does to your brain

Suntheanine L-Theanine is no different to any other type of L-Theanine when using the same dosages. That means that 200mg of Suntheanine L-Theanine will have exactly the same effects on the brain as 200mg of L-Theanine of the same purity.

In other words, Suntheanine affects the brain in exactly the same way as L-Theanine, since Suntheanine is just L-Theanine made in a certain way.

The acute effects of Suntheanine administration are:

  • Reduced brain fog
  • Enhanced focus
  • Reduced anxiety
  • Increase in Alpha brain wave activity
  • Improved sleep quality

Just like with other forms of L-Theanine, Suntheanine also reduces the side effects of caffeine while amplifying or potentiating its beneficial effects. This applies to other natural stimulants too.

Are Suntheanine and L-Theanine the same thing?

Essentially, yes. Suntheanine and L-Theanine are the same things. Suntheanine is just a branded, patented form of L-Theanine. The only difference between Suntheanine and other L-Theanine supplements is how the L-Theanine is obtained.

Most L-Theanine supplements are made by obtaining the amino acid from tea leaves via a natural process. Dry tea leaves are used as a source material and various methods are used to obtain pure L-Theanine from the powder.

Suntheanine, by contrast, is made by getting microbes to produce L-Theanine. This process is more scalable on an industrial level.

The positive effects of both Suntheanine and L-Theanine - the improved brain function, the sleep aid activity, and anti-stress effects - are exactly the same. How you obtain the L-Theanine doesn't matter, all that matters is the purity and the dose!

What is the purest form of L-Theanine?

There is no one single purest form of L-Theanine.

Some L-Theanine is obtained from the dried powder of black tea leaves. This is what we think of as regular L-Theanine. Other forms - i.e. Suntheanine - are made in a very elaborate way using microbes. But the "purity" of the end result is essentially the same in both cases (depending on how well the proces is controlled and monitored).

You may see some brands of L-Theanine in nooropic stacks which claim to deliver 10x more L-theanine because they are so much more bioavailable than regular L-Theanine. This is either a lie or a complete misunderstanding of the manufacturing process and what it means for L-theanine supplementation.

The purity of the L-Theanine you use will determine the degree of beneficial effects you experience. A purer L-Theanine, if dosed properly, will improve cognitive function more than a less pure L-Theanine. But most nootropics use highly pure L-Theanine. Suntheanine is not significantly purer than other L-Theanine products.

L-Theanine vs. Suntheanine® Side Effects: Is one safer than the other?

Neither Suntheanine nor L-Theanine are known to cause any serious side effects or adverse reactions whatsoever (assuming you're taking a sensible dose).

In every randomized, double-blind, placebo-controlled clinical trial done on acute L-theanine administration, no notable side effects are reported by the authors. Studies looking at chronic l-theanine administration have also not raised any real health or safety concerns.

That said, large doses of L-Theanine have been known to cause side effects. Some of the most common side effects of L-Theanine consumption include:

  • Elevated heart rate
  • Anxiety symptoms
  • Reduced attention span
  • Reduced mental clarity

These side effects are mostly associated with taking very large doses of L-Theanine or Suntheanine. They are also much more likely in people who are taking medications which have an effect on or relationship with glutamic acid.

Healthy people not on any medication and taking moderate doses of Suntheanine or L-Theanine should not experience any significant side effects from these supplements. That being said, it is vital that you talk to your doctor before using supplements containing L-Theanine in any form and to do your own research thoroughly.

Maximizing the Benefits of Theanine with Supplements

L-Theanine, an amino acid predominantly found in tea leaves, is celebrated for promoting relaxation without drowsiness. To elevate its cognitive and mood-enhancing effects, many individuals have turned to 'stacking' Theanine with other supplements.

  • Citicoline: Known to enhance brain energy and boost the synthesis of vital neurotransmitters, Citicoline combined with Theanine can amplify focus and mental clarity. This stack promotes better memory retention and quicker recall.

  • Caffeine: The synergy between Theanine and Caffeine is well-known. While Caffeine provides alertness and enhanced cognitive function, Theanine can moderate the jitters or restlessness that some people experience with caffeine. Together, they offer balanced energy and improved attention.

  • Tyrosine: An amino acid precursor to vital neurotransmitters like dopamine and norepinephrine, Tyrosine can further uplift mood and cognitive performance. When stacked with Theanine, the duo can counteract stress while promoting clear, calm focus.

  • B6: Vitamin B6 is essential for neurotransmitter synthesis. By augmenting the production of neurotransmitters, B6 can bolster the mood-enhancing and cognitive benefits of Theanine, creating a more robust and resilient mental state.

In conclusion, stacking Theanine with these supplements creates a harmonized blend that optimizes brain function, balances mood, and fosters a more productive mental state, making it a potent combination for cognitive enthusiasts.

L-Theanine vs. Suntheanine® Supplements: Which is better?

So what's the difference between L-Theanine and Suntheanine?

The answer is, "not much".

Clinical trials show absolutely no discernible difference between Suntheanine and L-Theanine, be it in terms of negative side effects, anxiety relief, cognitive enhancement, or synergy with caffeine.

L-Theanine use is highly recommended if you are looking for a safe and natural way to promote focus, get rid of brain fog and reduce anxiety. It makes caffeine more effective, promotes BDNF in the brain and even helps you sleep!

But don't be fooled by those claiming that Suntheanine is the best L-Theanine supplement. Any good quality L-Theanine supplement will give you the same benefits as Suntheanine but for a fraction of the cost!

What is much more important than worrying about Suntheanine vs L-Theanine is the way you stack L-Theanine with other substances, as well as the dosage and the quality of the product in question.


  • Baba, Yoshitake et al. “Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.” Journal of medicinal food vol. 24,4 (2021): 333-341. doi:10.1089/jmf.2020.4803
  • Owen, Gail N et al. “The combined effects of L-theanine and caffeine on cognitive performance and mood.” Nutritional neuroscience vol. 11,4 (2008): 193-8. doi:10.1179/147683008X301513

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