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Caffeine + L-Theanine: Does It Improve Your Workouts? (Explained)

Updated: Aug 16

TL;DR: L-theanine can reduce the jitteriness and anxiety associated with caffeine, while also improving focus more than either alone, possibly improving your workouts.

Caffeine and l-theanine are quite opposite supplements, caffeine is a stimulant and l-theanine is a sleep and relaxation promoting supplement. So how do they work together to improve workouts?

When combined with caffeine, l-theanine may reduce some of the stimulating effects of caffeine. The outcome is a boost in energy without the jittery side effects and crash associated with caffeine consumption.

In this article, I will explain the synergistic effects of l-theanine and caffeine and if they could help improve your workouts.

Table of Contents:

cup full of coffee beans

What Is Caffeine?

Caffeine is a naturally occurring stimulant found in tea, coffee, and cacao plants. It works by activating the brain and central nervous system, preventing fatigue and maintaining alertness.

Coffee was allegedly found by an Ethiopian shepherd who noted the increased energy it provided his goats. Historians trace the origins of tea back to 2737 B.C. (1)

The Food and Drug Administration (FDA) estimates that about 80% of the population consume some kind of caffeine every day.

Caffeine does much more than simply keep you awake, it is a central nervous system stimulant that has a variety of effects on your body.

How It Works

Caffeine is rapidly absorbed from the stomach into the circulation after consumption. It then goes to the liver, where it is broken down into chemicals that may influence the operation of different organs.

Caffeine's main effect, however, is on the brain. It works by inhibiting the effects of adenosine, a neurotransmitter that relaxes the brain and makes you tired. (2)

Normally, adenosine levels rise during the day, making you weary and wanting to sleep.

Caffeine keeps you awake by attaching to adenosine receptors in your brain but without activating them. This inhibits the effects of adenosine. It may also raise blood adrenaline levels and the activity of dopamine and norepinephrine in the brain. (3)

This combination stimulates the brain even more, promoting alertness, and focus. Caffeine is frequently referred to as a psychoactive substance because of how it affects your brain.

Furthermore, caffeine has a rapid onset of action.

For example, the quantity contained in one cup of coffee may enter the bloodstream in as short as 20 minutes and achieve maximum efficacy in around one hour. (1)

effects of caffeine infographic

To summarise; the primary impact of caffeine is on the brain. It stimulates the brain by preventing the neurotransmitter adenosine from acting. Adenosine's role in the brain is to slow its function.

Safety, Dosage & Side-Effects

Using caffeine is likely safe if only relatively small amounts are used, up to 400mg per day seems safe. One cup of brewed coffee has around 90-200 mg of caffeine.

Caffeine has been linked to sleeplessness, anxiety and restlessness, stomach discomfort, nausea, increased heart rate, and other side-effects.

Larger dosages may result in headache, anxiety, agitation, and chest discomfort. Overdosing on caffeine is very dangerous and potentially fatal.

What Is L-Theanine

L-theanine is an amino acid that is mainly present in green and black tea, as well as certain mushrooms. It's also available as a pill or tablet.

In terms of the brain, l-theanine is believed to help with the following.

  • Anxiety and stress relief (4, 5, 6)

  • Improve focus when combined with caffeine (7)

  • May reduce the jittery effects of caffeine

How It Works

L-theanine's function is to raise inhibitory neurotransmitter levels while also acting directly to prevent excitatory neurotransmitter overproduction.

L-theanine is a glutamic acid analogue, which is a chemical molecule that is comparable to the neurotransmitter glutamate.

Due to these functions, l-theanine may reduce anxiety and stress. (6)

However, there is not as much research into l-theanine and its function in the brain.

Safety, Dosage & Side-Effects

There have been no proven direct negative effects associated with the use of L-theanine. In general, it is safe to use teas and supplements containing L-theanine.

A typical dosage of l-theanine is either 100-400mg, or if combined with caffeine, a 1:1 ratio is used, for example; 200mg caffeine and 200mg of l-theanine.

Note: Avoid using more than 400mg of caffeine per day.

It should also be noted that the Food and Drug Administration (FDA) does not regulate dietary supplements. Manufacturers have the duty of ensuring that their products are safe.

Also, l-theanine may have interactions with certain medications, such as cancer treatments. You should speak with your doctor if you take this supplement.

Can This Supplement Stack Improve Your Workouts?

The combination of l-theanine and caffeine is usually a cognitive enhancers favourite nootropic, but it may also improve your workouts and exercise performance.

Caffeine has been known for a long time to improve strength and endurance. (8) L-theanine is an inhibitory supplement which reduces anxiety and stress. (6)

These two supplements may work synergistically, maintaining energy, focus, and concentration without the jittery side-effects associated with caffeine. (9)

However, the unique advantage of this stack is that l-theanine can enhance focus further than caffeine alone, allowing you to have a harder workout without losing focus.

In summary, it seems as though the combination of caffeine and l-theanine is able to improve focus more than caffeine alone.

It can also maintain energy while reducing the jitteriness and anxiety associated with caffeine intake.

Further Reading

> Should You Take Creatine & Beta-Alanine Together?

> Does Ursolic Acid Help You Gain Muscle?


This section contains links to research, studies, and sources of information for this article, as well as authors, contributors, etc. All sources, along with the article and facts, are subjected to a series of quality, reliability, and relevance checks.

Real Muscle primarily uses high-quality sources, such as peer-reviewed publications, to back up the information in our articles. To understand more about how we fact-check and keep our information accurate, dependable, and trustworthy, read more about us.

This evidence-based analysis of the synergy between l-theanine and caffeine features 9 references, listed below.

1. Heckman, M.A, Weil, J. and De Mejia, E.G. Caffeine (1, 3, 7-trimethylxanthine) in Foods: A Comprehensive Review on Consumption, Functionality, Safety, and Regulatory Matters. Journal of Food Science (2010) ✔

2. Dunwiddie TV, Masino SA. The role and regulation of adenosine in the central nervous system. Annu Rev Neurosci. (2001) (Review) ✔

3. Ferré S. An update on the mechanisms of the psychostimulant effects of caffeine. J Neurochem. (2008, May) (Review) ✔

4. Anna C Nobre, Anling Rao, and Gail N Owen. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. (2008)

5. J.M. Everett, D. Gunathilake, L. Dufficy, P. Roach, J. Thomas, D. Upton, N. Naumovski. Theanine consumption, stress and anxiety in human clinical trials: A systematic review. Journal of Nutrition & Intermediary Metabolism. (2016) (Review)

6. Michael S. Ritsner, Chanoch Miodownik, Yael Ratner, Tatyana Shleifer, Maria Mar, Leonid Pintov, Vladimir Lerner. L-Theanine Relieves Positive, Activation, and Anxiety Symptoms in Patients With Schizophrenia and Schizoaffective Disorder. Schizophrenia and Schizoaffective Disorders. (2009)

7. Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. (2010, Dec) (Randomised Controlled Trial) ✔

8. Grgic J, Trexler ET, Lazinica B, Pedisic Z. Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. J Int Soc Sports Nutr. (2018, Mar) ✔

9. Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. (2008, Aug) (Randomised Controlled Trial) ✔

Citations with a tick indicate the information is from a trusted source.


The information provided in this article is not intended to replace professional medical advice, diagnosis, or treatment. Always seek the guidance of a physician or other competent professional before following advice or taking any supplement. See our terms and conditions.

Real Muscle leads the way in terms of transparency and privacy, which is why we want to let you know that some of the outbound links in this article may be affiliate links in which we may earn a small commission through. Despite this, our product recommendations are completely unbiased.

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