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Time for tea: Mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together

Department of Experimental Psychology, University of Bristol, 12a Woodland Road, Bristol, BS8 1TU, UK.
Psychopharmacology (Impact Factor: 3.99). 02/2008; 195(4):569-77. DOI: 10.1007/s00213-007-0938-1
Source: PubMed

ABSTRACT Although both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats.
To study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers.
In a randomised, double-blind, placebo-controlled study, healthy adult participants (n = 48) received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task.
Caffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine also slowed overall reaction time on the visual probe task.
Theanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.

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    • "Interaction between caffeine and theanine may also be possible. For example, previous studies reported that the combined intake of caffeine and theanine may improve attention more than caffeine alone [33] [34]. Because our study addressed total injury deaths, it is likely that other substances contained in green tea played a role in reducing the risk of death other than accidental injuries, which may warrant further investigation. "
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    • "According to Yokogoshi and collaborators [108], Ltheanine is partially transported to the brain via a leucinepreferring transporter system and can cross the BBB exercising protective and preventive effects on neuronal cell death. The benefits of L-theanine for health are reported to be associated with regulation of blood pressure, effective prophylaxis and treatment for neurodegenerative diseases, among others [109] [110] [111]. "
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    Current Neuropharmacology 12/2014; 12(6). DOI:10.2174/1570159X13666141204220539 · 2.35 Impact Factor
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    • "Adenosine antagonism has been implicated as a contributor to the direct cardio-acceleratory effect of caffeine, which also increased blood pressure and respiration rate [12]. On the other hand, both caffeine and L-theanine were recently found to have beneficial effects on cognition and mood [13-15], but no study has compared these two components under conditions in which acute psychological and physical stresses increase blood pressure. "
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