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.

    • "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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    ABSTRACT: Background and Purpose: We examined the association between green tea consumption and mortality due to all causes, cancer, heart disease, cerebrovascular disease, respiratory disease, injuries and other causes of death in a large-scale population-based cohort study in Japan. Methods We studied 90,914 Japanese (aged between 40 and 69 years) recruited between 1990 and 1994. After 18.7 years of follow-up, 12,874 deaths were reported. The association between green tea consumption and risk of all causes and major causes of mortality was assessed using the Cox proportional hazards regression model with adjustment for potential confounders. Results Hazard ratios for all-cause mortality among men who consumed green tea compared with those who drank less than 1 cup per day were 0.96 (0.89 to 1.03) for 1 to 2 cups per day, 0.88 (0.82 to 0.95) for 3 to 4 cups per day, and 0.87 (0.81 to 0.94) for more than 5 cups per day (p for trend <0.001). Corresponding hazard ratios for women were 0.90 (0.81 to 1.00), 0.87 (0.79 to 0.96), and 0.83 (0.75 to 0.91) (p for trend <0.001). Green tea was inversely associated with mortality from heart disease in both men and women, and mortality from cerebrovascular disease and respiratory disease in men. No association was found between green tea and total cancer mortality. Conclusion This prospective study suggests that the consumption of green tea may reduce the risk of all-cause mortality and the three leading causes of death in Japan.
    Annals of Epidemiology 03/2015; 25(7). DOI:10.1016/j.annepidem.2015.03.007 · 2.15 Impact Factor
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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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    ABSTRACT: Diabetes mellitus (DM) is a metabolic disease that is rapidly increasing and has become a major public health problem. Type 2 DM (T2DM) is the most common type, accounting for up to 90-95% of the new diagnosed DM cases. The brain is very susceptible to glucose fluctuations and hyperglycemia-induced oxidative stress (OS). It is well known that DM and the risk of developing neurodegenerative diseases are associated. Tea, Camellia sinensis L., is one of the most consumed beverages. It contains several phytochemicals, such as polyphenols, methylxanthines (mainly caffeine) and L-theanine that are often reported to be responsible for tea’s health benefits, including in brain. Tea phytochemicals have been reported to be responsible for tea’s significant antidiabetic and neuroprotective properties and antioxidant potential. Epidemiological studies have shown that regular consumption of tea has positive effects on DM-caused complications and protects the brain against oxidative damage, contributing to an improvement of the cognitive function. Among the several reported benefits of tea consumption, those related with neurodegenerative diseases are of great interest. Herein, we discuss the potential beneficial effects of tea consumption and tea phytochemicals on DM and how their action can counteract the severe brain damage induced by this disease.
    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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    ABSTRACT: Background L-theanine, an amino acid contained in green tea leaves, is known to block the binding of L-glutamic acid to glutamate receptors in the brain, and has been considered to cause anti-stress effects by inhibiting cortical neuron excitation. Both L-theanine and caffeine, which green tea contains, have been highlighted for their beneficial effects on cognition and mood. Methods In this study, we investigated the effects of orally administered L-theanine or caffeine on mental task performance and physiological activities under conditions of physical or psychological stress in humans. Fourteen participants each underwent three separate trials, in which they orally took either L-theanine + placebo, caffeine + placebo, or placebo only. Results The results after the mental tasks showed that L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after placebo intake. Caffeine tended to have a similar but smaller inhibition of the blood-pressure increases caused by the mental tasks. The result of the Profile of Mood States after the mental tasks also showed that L-theanine reduced the Tension-Anxiety scores as compared with placebo intake. Conclusions The findings above denote that L-theanine not only reduces anxiety but also attenuates the blood-pressure increase in high-stress-response adults.
    Journal of PHYSIOLOGICAL ANTHROPOLOGY 10/2012; 31(1):28. DOI:10.1186/1880-6805-31-28 · 1.27 Impact Factor
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