Theanine or Caffeine? Soda, Black or Green Tea? What's Going to Get Your Brain Going? Plus: What About Sleep?

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.

"L-theanine, coffee or both? What's going to get your brain going?" That's the question form the title of today's SuppVersity article and it's a question with an astonishingly simple answer:  Both!

I guess you will be well aware that both caffeine and l-theanine have scientific evidence to support their usefulness as cognitive enhancers (Quinlan. 2000; Hindmarch. 2000; Nathan. 2006). Their interactions however have not been studied that extensively.

It's thus worth to take a closer look at the data Hira Zameer et al. collected for their most recent paper in the International Journal of Endorsing Health Science Research - data on the effects these agents can have on the cognitive performance and reaction times of 87 healthy young women (18-19 years), when they are consumed as part of hot and cold beverages (Zameer. 2013)

Compare to caffeine, which is literally on everyone's lips, only few people actually know what l-theanine is. Quite often you will see it being mislabled as the "the caffeine in tea" and that despite the fact that it is not even a methylxanthine, but (as the "L-" already suggests) an amino acid. Against that background it appears prudent to start today's SuppVersity article with a mini-summary of the the (astonishingly few) things we know about gamma-glutamylethylamide or 5-N-ethyl-glutamine, an amino acid and a glutamic acid analog that's - who would have guessed that - primarily found in tea.

L-theanine - the "tea caffeine"!?

L-theanine has gained quite some attention in the field of neuroscience. Kakuda et al., for example report significant neuroprotective effects in their 2002 paper. Protection is however not the only thing l-theanine can do for you. Previous studies have shown that it has direct beneficial effects on the activity of alpha frequency band (8–14 Hz), the cellular pacemaker of the human body (Kobayashi, 1998; Juneja, 1999).

Not to be confused: L-Theanine vs. theacrine as in "Theacrine Will Get You Going - Every Day! Camellia Kucha Alkaloid Acts via Dopamine and Adenosine" | more

In this context it's important to know that l-theanine has, in contrast to many other agents, the ability to cross the blood-brain barrier. It does so relatively easily, but not rapidly: Based on the current scientific evidence it takes ca. 30 minutes from the moment of its ingestion, before the first changes in neurotransmitter levels can be observed.

Structurally, L-theanine is similar to the excitatory neurotransmitter glutamic acid (Nathan. 2006). Consequently, L-theanine has the ability to antagonizes the central effects of glutamate by inhibiting glutamate reuptake and blockade of glutamate receptors in the hippocampus (Kakuda. 2002). This process goes hand in hand with an increased release of the "calming" neurotransmitter GABA and a concomitant decline norepinephrine levels.

In view of its GABA-ergic effects, it's not really surprising that L-theanine has also been found to ameliorate the blood pressure rising effects of caffeine and tone down the CNS responses (Eschenhauer. 2006) - quite a neat effect for an agent you get for free with your daily dose of caffeine in tea, isn't it?
In subjects who had to perform a standardized series of stressful tasks, L-theanine has been shown to reduce the heart rate and salivary immunoglobulin A release via direct inhibition of the excitation of cortical neurons (Kimura. 2007). With the close connection between stress exposure, the activation of the sympathetic nervous system and the ensuing release of vasoconstricting hormones, it is not unlikely to assume that L-theanine's blood pressure lowering effects are a simple result of its ability to buffer the CNS activity and reduce the adrenergic tone (Kulkarni. 1998; Matthews. 2004).

Enough of the past, let's get to the most recent results

Now that you are in the know about some of the most prominent effects of l-theanine consumption, let's see how it fares in a direct comparison to everyone darling - caffeine!

Figure 1: Effects of soda, (black) tea and green tea ingestion on reaction time, concentration test performance, blood pressure and heart & pulse rate (Zemeer. 2013)

I already mentioned that the subjects, 87 young adult females (18-19 years of age) were randomly assigned to three groups

• Group A consumed a cold beverages in the form of soft drinks (caffeine only)
• Group B consumed a serving of black tea (caffeine + l-theanine)
• Group C consumed a serving of green tea (min. caffeine + l-theanine)

Before and 45 min after the beverage ingestion the scientists monitored the cardiovascular and neurophysiological responses. After the "immediately post" data had been collected, all participants engaged in a series of standardized reaction time and concentration tests that yielded astonishingly similar results:

• Both tea preparations "proved to be more sufficient in enhancing concentration and focusing power of the individuals by reducing the distractions during a task at hand" (Zemeer. 2013)
• The concentration levels during a passage reading task in the tea condition were likewise significantly higher (p < 0.05) than in the soft drink condition, which had only marginal effects on the subjects' ability to focus.

The analysis of the cardiovascular parameters, on the other hand, showed that all groups experienced a decline in systolic blood pressure, surprisingly,

Ever wondered about the "exact" pharmacology of caffeine? Tom Edwards captured it in 1990.

"[...] a significant reduction in systolic blood pressure by 13 and 19 mm Hg was evident amongst the candidates of group A and C who were assigned for the intake of soft drink (caffeine) and green tea (L-theanine), respectively (p < 0.05) as compared to individuals who were belonged to tea (caffeine + L theanine) consumption group. Similarly, a considerable decline in diastolic blood pressure by 12 mm Hg was more noticeable among the participants who were subjected to consume soft drink (caffeine) and green tea (L-theanine) (p < 0.05) as compared to the group B, tea consumers.

Physiological rise in the heart rate of the individuals was observed when their basal heart rates were taken before and after consumption of hot and cold beverages. But a less significant rise in heart rate by 1bpm was remarkable among group C (L-theanine) candidates (P=0.31). In contrast to heart rate, a significant increase in pulse rate by 10 bpm was reported within the members of group C, green tea (L-theanine) consumers (P=0.01). " (Zemeer. 2013)

If you look back at my brief summary of the current data on l-theanine in the upper part of this article, you will probably find the increase in blood pressure and the modulatory effects on the heart rate of the subjects odd - in the end, it is however perfect evidence that the effects of neurotransmitters and agents that can influence their levels and ratios are hard, if not impossible to predict. As with GABA (see "SuppVersity Science Round-Up: Paradoxical Effects of GABA. Plus: GABA-Alternatives" | read more) it may thus well be that tea really psyches you up and a "simple" coffee, where caffeine runs the whole show, is much better suited for you than a huge cup of black or green tea.

References:

• Eschenauer G, Sweet BV. Pharmacology and therapeutic uses of theanine. Am J Health Syst Pharm. 2006 Jan 1;63(1):26, 28-30.
• Hindmarch I, Rigney U, Stanley N, Quinlan P, Rycroft J, Lane J. A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality. Psychopharmacology (Berl). 2000 Apr;149(3):203-16.
• Nathan PJ, Lu K, Gray M, Oliver C. The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother. 2006;6(2):21-30. 
• Kakuda T, Nozawa A, Sugimoto A, Niino H. Inhibition by theanine of binding of [3H]AMPA, [3H]kainate, and [3H]MDL 105,519 to glutamate receptors. Biosci Biotechnol Biochem. 2002 Dec;66(12):2683-6. 
• Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45.
• Kulkarni S, O'Farrell I, Erasi M, Kochar MS. Stress and hypertension. WMJ. 1998 Dec;97(11):34-8. Review.
• Kuriyama S, Shimazu T, Ohmori K, Kikuchi N, Nakaya N, Nishino Y, Tsubono Y, Tsuji I. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006 Sep 13;296(10):1255-65.
• Quinlan PT, Lane J, Moore KL, Aspen J, Rycroft JA, O'Brien DC. The acute physiological and mood effects of tea and coffee: the role of caffeine level. Pharmacol Biochem Behav. 2000 May;66(1):19-28.
• Zameer et a.. Comparative Effects Of Caffeine & L-Theanine Consumption On Subjective Cardiovascular Signs And Neurophysiological Responses. International journal of endorsing health science research. 2013; 1(1): 38-42.