Cognitive Effects of Caffeine and L-Theanine

Theanine is a compound that has similarities to amino acids such as L-glutamine which might help gut function, your immune system, and it provides “fuel” (nitrogen and carbon) to many different cells in your body. Theanine can be found in certain plants and fungal species, as well as green tea. In common preparations, such as teas and supplements, Theanine is absorbed in the small intestine after oral ingestion. It can also cross the blood-brain barrier intact.


Many of us have ingested caffeine and experienced the jitters that come along with it. As well, some people experience high blood pressure, dehydration, trouble sleeping and increased anxiety. Ingesting caffeine and Theanine together can help reduce or even eliminate the negative effects of caffeine alone.There have been numerous studies done indicating that Theanine has positive impacts on mood, relaxation and alertness. Especially when taken with caffeine, the combination can improve focus and attention span. First I will discuss some researcher that has been done on Theanine, as well as Theanine taken with caffeine, and then I will discuss when and how much of each to take.


Research done in the journal of Nutritional Neuroscience by Gail N. Owen, Holly Parnell, Eveline A. De Bruin and Jane A. Rycroft studied the combined effects of L-Theanine and caffeine on cognitive performance and mood. This study was done to compare 50mg of caffeine, with and without 100 mg of L-Theanine on the cognition and mood of healthy volunteers. Researchers wanted to test the effects of the combination of caffeine and Theanine on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood, and compared the results to a placebo in 27 participants. Performance was measured at the baseline, 60 min interval, and 90 min after each treatment, and these treatments were separated by a 7-day washout period. Caffeine alone improved subjective alertness at the 60 min interval, and accuracy on the attention-switching task at the 90 min interval. The combination of Theanine and caffeine improved both speed and accuracy of performance of the attention switching task at 60 mins, and reduced susceptibility to distracting information in the memory task at both the 60 min and 90 min interval.  


Consuming caffeine alone cause us to get a jolt of energy, but we may find it hard to focus on one task. Caffeine causes our Beta wave brain function, which is responsible for for alert, energetic, and distracted type thinking, to increase. L-Theanine encourages alpha wave brain function, which is typically created when we are daydreaming or consciously practicing mindfulness or meditation. The bonus is that L-Theanine overrides caffeine’s stimulatory effects that promote beta wave function.Theanine can enhance your alpha brain wave activity, and consequently your mood, relaxation and alertness. Studies done at Unilever Food and Health Research Institute tested that L-Theanine significantly increases activity in the alpha frequency band which indicates that it relaxes the mind without inducing drowsiness.


Another study done at the Cognitive Neurophysiology Laboratory in New York used 100 mg of L-Theanine and 50 mg of caffeine to measure both cognitive behaviour, as well as brain waves in 16 healthy subjects. Subjects were given either a placebo, 100 mg of L-Theanine, 50 mg of caffeine, or L-Theanine and caffeine combined. They were tested each day for 4 consecutive days. The theanine alone, nor the caffeine alone had any discernible effects, however, together they improved the subjects performance on cognitive tests. Brain waves were also tested in the subjects, and alpha brain wave activity increased in those taking the combination of theanine and caffeine. Alpha brain waves are associated with effortless alertness, and are believed to be the underlying mechanism for the cognitive benefits.


How to:

To supplement caffeine and L-theanine:

  • for veteran coffee drinkers, take 200 mg of each supplement 30 minutes before you need increased focus and attention
  • People that are not used to caffeine should start with a 100 mg L-theanine dose taken alongside 50 mg of caffeine
  • Taking caffeine and L-theanine on an empty stomach can increase the rates of absorption. If this upsets your stomach, please take with food.



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