L-Theanine is the naturally occurring amino acid in green tea that adds a savory note to every comforting sip. It has long been prized for its calming effect and gentle ability to promote stress resilience, help reduce occasional anxiety, and promote restful sleep—all without sedation. For this reason, dietary supplements containing L-theanine are popular among folks looking for support to stay calm, relaxed, and focused—not to mention enjoy restful sleep.

If you’ve ever taken a regular L-theanine supplement, you know it goes to work in a matter of minutes. You also know it fades fast. That’s because, while L-theanine is highly effective, its fast-acting nature is also its biggest limitation—unless it's formulated for gradual absorption.

How L-Theanine Works

L-theanine is a water-soluble amino acid. Some scientists call it L-gamma-glutamylethylamide; others call it 5-N-ethyl-glutamine. Whatever you call it, it has a remarkable ability to cross the blood-brain barrier easily and quickly. Once in the brain, L-theanine helps modulate key biochemical pathways involved in your ability to stay calm, relaxed and focused (1):

• L-theanine is a biochemical cousin to glutamate, an excitatory brain chemical (neurotransmitter) that helps neurons communicate. It binds to glutamate receptors, calming their activity, which can help you manage stress.

• L-theanine promotes alpha brain waves, which are linked to a relaxed, yet alert, state of mind. 

• L-theanine promotes the optimal activity of GABA—the brain’s main calming chemical—to help reduce occasional anxiety, support relaxation, and promote restful sleep.

• L-theanine helps balance levels of dopamine, a neurotransmitter that plays a key role in motivation, and serotonin, a neurotransmitter that plays a key role in mood and emotional well-being. 

This brain chemical balancing act is a key reason many people feel noticeably calm within 30-45 minutes after taking an L-theanine supplement.

The Problem: Regular L-Theanine Works Fast, But It Doesn’t Last

Here’s the catch: When you take a regular L-theanine supplement, it’s quickly absorbed but also quickly cleared from your body. Because it dissolves well in water, scientists say it has a “short half-life,” lasting just 1 to 2 hours in your bloodstream before the kidneys remove it.

That means:

• Its calming effects peak quickly, but drop off soon after

• Frequent dosing is required throughout the day for consistent support

• When taken at bedtime, it may help you fall asleep, but doesn’t help you stay asleep through the night

One study clearly shows this vanishing act in action. For this study, university researchers compared how healthy men and women process a 100-mg dose of L-theanine as a pure powder in a capsule or from green tea (2). Both forms were absorbed surprisingly quickly—within 10 to 24 minutes—and hit their peak blood level around 48 minutes. After that, levels dropped off pretty fast, with more than half gone after about 3 hours.

Other researchers report a similar trend in healthy men: L-theanine from either green tea or pure form is quickly absorbed and eliminated from the blood (3). This pattern of rapid absorption, rapid elimination is also seen in laboratory mice (4). If you’re seeing a theme here, your right. Keeping L-theanine levels steady in your bloodstream requires next-level formula innovation.

The Solution: Controlled-Release L-Theanine

For an L-theanine supplement to work effectively, you need to start with a quality ingredient like the Suntheanine® brand. Rather than made in the lab using standard chemical methods, this special form is produced through enzymatic fermentation—a natural process that mimics how green tea plants make L-theanine. We really like this approach, which is why our product formulators chose this form for EndurPro™ L-Theanine SR. 

Next, to make L-theanine last longer in the body, a controlled-release (or sustained-release) delivery form is needed—but not just any delivery form will do. We chose a vegetable wax-matrix tablet (similar to the one used in extended-release niacin) because it has the unique ability to gradually release L-theanine over 7-8 hours to promote the optimal absorption needed for long-lasting support.

The result is an easy-to-swallow tablet that skips sugary or harsh chemical coatings and synthetic binders, plus it’s free from artificial colors, flavors, and preservatives. As the tablet travels through your digestive tract,  the gentle vegetable wax matrix slowly releases L-theanine for absorption by the cells that line your intestines. In this way, it promotes steady, lasting benefits.*

How to Take EndurPro™ L-Theanine SR for Best Results

For daytime calm and focus:*

• Suggested Use: 200-400 mg, two times daily (morning and mid-afternoon) 

• A controlled- or sustained-release form provides smoother, more consistent absorption of L-theanine (and fewer doses), which can help avoid sharp spikes and drops in blood levels. 

For sleep support:*

• Suggested Use: 200-400 mg, 30-60 minutes before bed

• A controlled- or sustained-release form supports steady absorption of L-theanine over several hours to help you fall asleep and stay asleep for longer.  

Who Can Benefit Most from L-Theanine?

L-theanine is ideal for individuals with occasional:

• feelings of anxiety or racing thoughts

• sensitivity to overstimulation or sensory input

• difficulty falling or staying asleep

• mood fluctuations

• sensitivity to stimulants or difficulty focusing

And the best part? L-theanine works to promote calm without causing sedation, dependence, or tolerance—making it safe for daily and long-term use. This means it can be used regularly without worries about feeling sleepy or needing to increase the dose over time for the same benefits.

Final Thoughts

L-theanine is one of the most research-backed options for calming the mind, promoting focus, and supporting restful sleep. But for lasting effects, the delivery method matters. Fast-acting forms can offer a quick reset, but for support that lasts for hours, a controlled-release wax-matrix tablet is the new gold standard.

If you want to learn more about EndurPro™ L-Theanine SR and how it can support your emotional wellbeing and restful sleep, be sure to talk with your doctor.

Your brain will thank you—and so will everyone around you.

References

1. Wang L, Brennan MA, Li S, Zhao H, Lange KW, Brennan CS. How does the tea L-theanine buffer stress and anxiety. Food Sci Hum Wellness. 2022;11(3):467-475. doi:10.1016/j.fshw.2022.05.004

2. Scheid L, Ellinger S, Alteheld B, et al. Kinetics of L-theanine uptake and metabolism in healthy participants are comparable after ingestion of L-theanine via capsules and green tea. J Nutr. 2012;142(12):2091-2096. doi:10.3945/jn.112.166371

3. van der Pijla PC, Chen L, Mulder TPJ. Human disposition of L-theanine in tea or aqueous solution. J Funct Foods. 2010;2(4):239-244. doi:10.1016/j.jff.2010.09.002

4. Yamaura S, Sadamori K, Konishi R, et al. Pharmacokinetics of L-theanine and the effect on amino acid composition in mice administered with L-theanine. Amino Acids. 2024;56(1):29. doi:10.1007/s00726-024-03389-3

Suntheanine® is a registered trademark of Taiyo International, Inc.