Psychological effects of dietary components of tea: caffeine and L-theanine.

School of Psychology, University of South Australia, Adelaide, 5001, South Australia, Australia.
Nutrition Reviews (Impact Factor: 4.6). 03/2008; 66(2):82-90. DOI: 10.1111/j.1753-4887.2007.00011.x
Source: PubMed

ABSTRACT This review summarizes the literature on the association between two dietary components of tea, caffeine and L-theanine, and the psychological outcomes of consumption; it also identifies areas for future research. The studies reviewed suggest that caffeinated tea, when ingested at regular intervals, may maintain alertness, focused attention, and accuracy and may modulate the more acute effects of higher doses of caffeine. These findings concur with the neurochemical effects of L-theanine on the brain. L-theanine may interact with caffeine to enhance performance in terms of attention switching and the ability to ignore distraction; this is likely to be reflective of higher-level cognitive activity and may be sensitive to the detrimental effects of overstimulation. Further research should investigate the interactive effects of caffeine, L-theanine, and task complexity, utilize a range of ecologically valid psychological outcomes, and assess the neuroprotective effects of L-theanine using epidemiological or longer-term intervention studies among individuals at risk of neurodegenerative disease.

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    ABSTRACT: Two types of instant teas produced from low- and high-quality black teas were examined for their proximate composition, dietary fiber, minerals, water-soluble vitamins, total phenolic content, various antioxidant assays, phenolics (flavanols, condensed phenolics, and phenolic acids), alkoloids, and carotenoids as well as taste-active compounds (sugars, organic acids, and free amino acids). Some variations, albeit to different extents, were observed (p < 0.05) among these parameters between instant teas produced from low- and high-quality black teas. With respect to proximate composition, carbohydrate was the predominant component (56.68-59.84 g/100 g), followed by protein (19.31-19.86 g/100 g). Ash, moisture, and, to a lesser extent, dietary fiber and fat were also present in both instant teas. Thirteen minerals, four water-soluble vitamins, six flavanols, two alkoloids, three condensed phenolics, one phenolic acid, and one carotenoid were identified. Total phenolic content varied between 17.35 and 17.82 g of gallic acid equivalents (GAE)/100 g instant tea. With regard to antioxidant activities, three different assays such as oxygen radical absorbance capacity (ORAC), trolox equivalent antioxidant capacity (TEAC), and cupric ion reducing antioxidant capacity (CUPRAC) were measured. No significant differences (p > 0.05) in total phenolic, ORAC, TEAC, and CUPRAC contents between low- and high-quality instant teas were observed. Regarding taste-active compounds, three sugars, five organic acids, and 18 free amino acids were positively identified, of which fructose, tannic acid, and theanine predominated, respectively. The present work suggests that despite some differences, instant teas produced from low- and high-quality black teas should not be distinguished on the basis of their compositional, nutritional, and functional characteristics as well as taste-active compounds.
    Journal of Agricultural and Food Chemistry 07/2013; · 3.11 Impact Factor
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    ABSTRACT: A fast RP-HPLC-DAD method has been developed and validated for simultaneous analysis of major bioactive constituents of tea. The collective separation of theanine, caffeine and catechins have been achived by using a new hydrophobic selective C12 stationary phase. The separation was done without any pre-column derivatization and using simple gradient solvent system of acetonitrile and water containing 0.01% TFA. We have achived rapid separation of all these components within 16 minutes with very good peak resolution and sensitivity. The method also exhibits very good linearity with correlation coefficients between 0.9918-0.9999 for all the compounds. A comparative assesment study for the estimation of above mentioned phytoconstituents from different solvent extracts as well as brewed infusions of green and black teas was also performed using this LC method. The results of the comparative evalution studies have showed that green tea extracts and brewed green tea infusions contain high yield of these phytoconstituents in comparison to black teas. The present HPLC method is quite applicable for biochemical analysis of wide range of tea samples including various types of teas, tea extracts, tea infusions, instant teas, RTDs and various other tea based value added food products and nutraceuticals and beverages.
    Journal of Liquid Chromatography &amp Related Technologies 01/2014; · 0.57 Impact Factor
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    ABSTRACT: This study explored whether drinking tea "treated" with good intentions would enhance mood more than drinking ordinary tea, under double-blind, randomized conditions. Each evening, for seven days in a row, volunteers recorded their mood using the Profile of Mood States (POMS) questionnaire. On days three, four, and five of the test, each participant drank 600mL of oolong tea in the morning and again in the afternoon. One randomly assigned group blindly received tea that had been intentionally treated by three Buddhist monks; the other group blindly received untreated tea from the same source. On the last day of the test, each person indicated what type of tea he/she believed he/she had been drinking. Stratified, random sampling was used to assign 189 adults into two groups matched by age, gender, the psychological trait of neuroticism, and the amount of tea consumed on average per day. All participants were Taiwanese and lived in Kaohsiung, Taiwan, and the test was conducted over the course of one week to reduce mood fluctuations due to changes in local weather and other common influences. Those who drank treated tea showed a greater increase in mood than those who drank untreated tea (Cohen's d = 0.65, P = .02, two-tailed). Change in mood in those who believed that they were drinking treated tea was much better than those who did not believe (Cohen's d = 1.45, P = .00002, two-tailed). Tea treated with good intentions improved mood more than ordinary tea derived from the same source. Belief that one was drinking treated tea produced a large improvement in mood, but only if one was actually drinking the treated tea, indicating that belief and intentional enhancement interact. This also suggests that the esthetic and intentional qualities associated with the traditional tea ceremony may have subtle influences that extend beyond the ritual itself.
    EXPLORE The Journal of Science and Healing 01/2013; 9(6):355-60. · 0.92 Impact Factor


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