Theanine + Caffeine - A Natural and Powerful Combination to Increase Your Attention and Reaction Speed (+6-10%)

Tea will naturally contain both theanine and caffeine, but will it work, as well as supplemental theanine and caffeine?
While everybody knows caffeine (see last SV article comparing caffeine to coffee), theanine aka L-γ-glutamylethylamide or N5-ethyl-L-glutamine, an amino acid analogue of the proteinogenic amino acids L-glutamate and L-glutamine, is less well known, but as a recent study shows not less potent when it comes to its effects on cognition and neurophysiological measures of selective attention aka "focus" on a task / object (Kahathuduwa. 2016).

You want to know why the researchers from the Universities of Peradeniya, Kelaniya and the Texas Tech University know that? Let's take a look at what the researchers did and why they conclude that the effects of caffeine & theanine add up.
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In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, Chanaka N. Kahathuduwa et al. compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive and neurophysiological measures of attention.
Figure 1: Theanine and caffeine contents of 37 commercial white, green, oolong, black, and pu-erh tea samples were quantified by high-performance is a liquid chromatography-diode array detector (Boros. 2016).
To get practically relevant results, the authors used simple [SVRT] and recognition visual reaction time tests, as well as neurophysiological (event-related potentials [ERPs]) measures of attention and recorded the visual (VEPs) and motor evoked potentials (MEPs) of their subjects after ingesting each of the three treatments.
Mean ± SE amounts of l-theanine in cups (200 ml) of commercially-available teas. Mean amounts of l-theanine (mg/200 ml) are also shown in brackets (Keenan. 2011) | rel. values for matcha tea are in the text.
What else can theanine do for you / how much is in tea? As the authors of a not exactly unbiased 1999 review (Juneja. 1999) conclude, theanine is a "unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ‘green’ tea". In the brain, theanine appears to act as an inhibitory neurotransmitter that reduces blood pressure; probably by modulating α-waves, which are associated with relaxation. In humans these effects have been shown to occur 40 min after the oral administration of theanine (50–200 mg), without causing drowsiness, however. It should be obvious that this makes theanine the perfect adjunct to caffeine which is known for making people jittery when consumed in doses large enough to elicit significant ergogenic and/or nootropic effects.
On the left hand side, you can see an overview of the theanine content of various commercial teas; in this context it is also worth pointing out that high grate matcha tea contains ~56% more than std. sencha green tea (for low grade gree tea, it's even more than 100% extra theanine in matcha vs. sencha | Goto. 1996).
Lastly, I would like to point out that theanine is not just the "calming" partner of caffeine, more recent research shows that l-theanine has neuroprotective, nootropic, immune-modulating, anti-fatigue, anti-diabetic and anti-depressant effects that are almost on par with caffeine. If you want to learn more about these, check out Liang's latest review (Liang. 2015)
What they found were statistically significant improvements in recognition visual reaction time (RVRT) in response to by theanine (P = 0.019), caffeine (P = 0.043), and theanine–caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). A result that is in line with previous research by Haskell, et al. form 2008.
Figure 2: Pre- ad post recognition visual reaction time (RVRT) latency and P110 visual evoked potential latencies, a measure of the reaction speed of your brain; abs. values in ms, rel. changes in % above the bars (Kahathuduwa. 2016).
Additive benefits for the combination of caffeine and theanine were observed not just for the recognition visual reaction time, but also for other parameters - including the P300 event-related potential amplitudes, an objective measure brain activity of the subjects that refutes the sometimes heard claim that theanine calm down your brain activity too much. At least in combination with caffeine, it's quite clear that the opposite is the case.
Caffeinated soft drink, coffee or tea, caffeine alone or caffeine + l-theanine what's going to yield the desired afterburner effect for your brain? The answer to this question came out probably less straight forward than you'd expected | learn more
Bottom line: For the authors their observations are evidence enough to prove "that high doses of theanine and caffeine have acute [beneficial effects on] attention" (Kahathuduwa. 2016). The authors do yet also point out that further research is necessary to figure out the dose–response relationship, as well as the time-course of theanine supplementation on objective measures of attention.

What I personally find even more interesting, though, is the fact that the evidence clearly indicates that "theanine and caffeine have additive effects" (Kahathuduwa. 2016)... ok, you probably expected that, in view of the fact that they are natural synergists in tea. Against that background, it appears strange that the scientists found no improvements in attention when they gave their subjects tea. The reason for the lack of effects is yet simple: the amount of theanine and caffeine used in the study are equivalent to the amounts found in 6–10 and 2-4 cups of tea, respectively.

Due to the relatively low theanine content of regular tea, even two cups of green, white or black tea will thus only cut it, if you add extra theanine (and a sprinkle of caffeine) to it | Comment!
  • Boros, Klára, Nikoletta Jedlinszki, and Dezső Csupor. "Theanine and Caffeine content of infusions prepared from commercial tea samples." Pharmacognosy Magazine 12.45 (2016): 75.
  • Goto T., Yoshida Y., Amano I., Horie H., Foods Food Ingredients J. 170 (1996): 46-51. 
  • Juneja, Lekh Raj, et al. "L-theanine—a unique amino acid of green tea and its relaxation effect in humans." Trends in Food Science & Technology 10.6 (1999): 199-204.
  • Haskell, Crystal F., et al. "The effects of L-theanine, caffeine and their combination on cognition and mood." Biological psychology 77.2 (2008): 113-122.
  • Kahathuduwa, Chanaka N., et al. "Acute effects of theanine, caffeine and theanine–caffeine combination on attention." Nutritional Neuroscience (2016): 1-9.
  • Keenan, Emma K., et al. "How much theanine in a cup of tea? Effects of tea type and method of preparation." Food chemistry 125.2 (2011): 588-594.
  • Liang, Yue-Rong, et al. "Health Benefits of Theanine in Green Tea: A Review." Tropical Journal of Pharmaceutical Research 14.10 (2015): 1943-1949.
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