Caffeine + L-Theanine Background

Caffeine + L-Theanine Background



L-Theanine is a fairly rare phytochemical and a non-dietary amino acid found primarily in a small number of mushrooms and in common tea, Camellia sinensis. For thousands of years, people in the East have used strong tea as a health-promoting and calming drink. Without knowing it, they were tapping into the benefits of L-Theanine. These include the ability to help reduce stress, improve mood and mental focus, boost your sleep quality, and promote a healthy circulatory system through its powerful antioxidant effects. [1]

Caffeine is even better known than L-Theanine. With coffee being the world’s most consumed drink, most people have a good understanding of Caffeine’s effects. It is energizing and stimulating, with noticeable improvements in mood and cognitive performance. The Caffeine compound is known as a purine alkaloid and is found predominantly in Coffea Arabica (the ‘coffee tree’), which is a dark green shrub that is indigenous to Ethiopia. [2]

Caffeine is a stimulant with potentially dangerous properties at high doses. It acts as a vasoconstrictor, meaning it increases blood pressure while improving focus and energy. A cup of coffee generally contains around 60mg of pure caffeine. More than 6 cups of coffee can be dangerous, and pure caffeine needs to be used very carefully to avoid potentially negative side effects. [3]



Caffeine + L-Theanine Effects/Benefits

The overall benefits and effects of Caffeine + L-Theanine capsules can be summarized into three categories, namely, the benefits of L-Theanine alone, Caffeine alone, and the benefits of combining the two.

Benefits of L-Theanine

Powerful Antioxidant Effects:

Studies have shown that L-Theanine has protective effects on the liver due to its ability to act as a powerful antioxidant. Alcohol consumption increases the amount of toxic chemicals called ‘free-radicals’ in your body. These cause harm to your liver and other organs. In 2012, scientists showed that L-Theanine has a significant protective effect on the liver by helping your body to destroy free-radicals. [4]

May Help Boost Mental State:

Studies have shown that the consumption of L-Theanine significantly increases the activity in alpha-frequency brainwaves in humans. Alpha brainwaves are associated with a relaxed, but alert state of mind. These effects are especially noticeable in concentrations that are higher than what you’d find in a cup of tea, for example. Alpha brainwave activity is thought to play an important role in attention and mental focus. [5]

Helps to Reduce Feelings of Stress:

Human studies have shown that supplementing with L-Theanine can reduce your response to stress. In one study, volunteers took an L-Theanine supplement and were presented with a stressful stimulus. The results showed lower heart rate and salivary immunoglobulin (s-IgA) for those who used L-Theanine. These are critical aspects of the stress response. [6]

Benefits of Caffeine

Energizing and Stimulating

Caffeine has powerful effects on the central nervous system (CNS). Through these effects, it is able to generate positive and noticeable effects on mental activity. It is particularly effective in activating noradrenaline receptors and affecting the release of dopamine. Essentially, caffeine increases mental and physical energy while improving mental stimulation and alertness. [7]

Improves Mood 

People have known for a long time that caffeine can be used to improve mood. A single cup of coffee produces, for many people, noticeable effects on their state of mind and feelings of well-being. Numerous studies have been conducted to evaluate the mechanisms and the scientific soundness of these claims. Needless to say, there is now empirical evidence that Caffeine significantly helps to boost mood. [8]

Boosts Physical Energy and May Help Maintain a Healthy Metabolism

In a recent study, the effects of caffeine on energy levels and thermogenesis (production of heat in the body, as a result of increased metabolism) were studied. In the study, twelve healthy participants were given either Green Tea Extract, Tyrosine, or Caffeine (50 mg). Of the three substances used, only Caffeine produced a significant increase in thermogenesis. This means that Caffeine can be used to boost metabolism and physical energy/endurance. Furthermore, this evidence suggests that people may consider using Caffeine in addition to a healthy diet as a means of promoting weight-loss. [9]

Benefits of Using L-Theanine with Caffeine

Best of Both

When you take a supplement containing both Caffeine and L-Theanine, you’ll be getting the benefits of both these great compounds. This means you’ll feel noticeable improvements in mood, memory, and stress-reduction, while also feeling mentally stimulated and energized. This is definitely one of the top supplement stacks available today!

Help Mitigate Potential Negative Effects of Caffeine

Studies into the effects of using L-Theanine with Caffeine tend to point to a highly synergistic relationship between the two. In one study, researchers found that L-Theanine helped to reduce the vaso-constrictive effects of Caffeine. In effect, this means that L-Theanine may help to reduce some of the potentially dangerous effects of Caffeine, especially for people with high blood pressure. [10]

Boost Cognitive Performance 

A number of studies have researched the synergistic effects of L-Theanine and Caffeine in combination, especially for your mental state. In one such study, researchers found that taking Caffeine with L-Theanine significantly improved cognitive performance and mood, while reducing the effects on heart-rate and blood pressure that are noticeable when using caffeine alone. [11] 

In a similar study, researchers found that taking L-Theanine with Caffeine helped to reduce the adverse effects of both. This means fewer people reported headaches (which was common with high doses of L-Theanine). Furthermore, the combination improved Rapid Visual Information Processing (RVIP) accuracy scores better than either supplement alone, and also reduced ‘mental fatigue’ ratings. The results suggest a significant improvement in cognitive performance when using a combination of L-Theanine and Caffeine. [12]

Caffeine + L-Theanine Recommended Usage

The serving size of our Caffeine + L-Theanine capsules is 250 mg, each containing 150 mg of L-Theanine and 100 mg of Caffeine. The recommended dosage is 1-2 capsules, once to twice daily. Always start with a lower dosage to assess your response to the supplement. Do not exceed the recommended serving size.

Caffeine + L-Theanine side effects and warnings 

Large doses of Caffeine can cause nervousness, headache, tremor, spasms, palpitations, high blood pressure, insomnia, and indigestion. Furthermore, very high doses of Caffeine can cause potentially fatal overdose symptoms.

Caffeine may not be suitable for people with a number of varying ailments. This includes people with anxiety disorders, bipolar disorder, bleeding disorders, heart conditions, diabetes, epilepsy, diarrhea, glaucoma, high blood pressure, irritable bowl syndrome, or osteoporosis. If you have any medical issues, please consult your doctor before using a Caffeine supplement. [13]

Caffeine is also known to be addictive and withdrawal symptoms from prolonged caffeine use are common. Withdrawal effects may include headaches, irritability, anxiety, dry mouth, and nausea.[14] To avoid withdrawal symptoms, do not use high doses of Caffeine capsules for prolonged periods of time.


In summary, Caffeine + L-Theanine pills are a great way to improve mental energy, wakefulness, and focus. Caffeine is one of the world's most widely consumed stimulant compounds, while L-Theanine is a potent calming and cognition-enhancing supplement found naturally in tea and mushrooms sources. Research shows that these two supplements have a great synergistic relationship when taken together, with L-Theanine helping to reduce some of the jitteriness of Caffeine, and both helping to support healthy cognitive performance and memory. The recommended serving size for this supplement is 1 - 2 capsules, once to twice daily. Do not use this supplement before sleep as Caffeine may keep you awake. Do not exceed the recommended serving size. Side effects are more noticeable at higher doses. 



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[2] Caffeine,, available online from [Accessed November 14, 2017]

[3] Caffeine: How much is too much?, available online [Accessed November 14, 2017]

[4] Li, G., et al., l-Theanine prevents alcoholic liver injury through enhancing the antioxidant capability of hepatocytes. Food Chem Toxicol. 2012 Feb;50(2):363-72.

[5] Nobre, A.C., Rao, A., Owen, G.N., L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-8.

[6] Kimura, K., Ozeki, M., Juneja, L.R., Ohira, H., L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45. Epub 2006 Aug 22.

[7] Glade, M.J., Caffeine-Not just a stimulantNutrition. 2010 Oct;26(10):932-8

[8] Smith, A., Sutherland, D., Christopher, G. Effects of repeated doses of caffeine on mood and performance of alert and fatigued volunteersJ Psychopharmacol. 2005 Nov;19(6):620-6.

[9] Belza, A., Toubro, S., Astrup, A., The effect of caffeine, green tea and tyrosine on thermogenesis and energy intakeEuropean Journal of Clinical Nutrition (2009) 63, 57–64 (2009)

[10] Dodd, F.L., et al., A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood.Psychopharmacology (Berl). 2015 Jul;232(14):2563-76.

[11] Giesbrecht, T., et al., The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertnessNutr Neurosci. 2010 Dec;13(6):283-90

[12] Haskell, C.F., et al., The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol. 2008 Feb;77(2):113-22. Epub 2007 Sep 26.

[13] Caffeine: Side Effects,, available online. [Accessed November 14, 2017]

[14] Caffeine Myths and Facts,, available online [Accessed November 14, 2017]