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Study Title and Description

Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses.
Author A Yoto,M Motoki,S Murao,H Yokogoshi,
Country
Year 2012
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? 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.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) A cross-over, randomized, placebo-controlled design was used in this study. In total, three separate trials were performed, in which the participants orally took either Ltheanine (200 mg, Taiyo Kagaku Co., Tokyo, Japan) + placebo, caffeine (100 mg, Shiratori Pharmaceutical Co., Chiba, Japan) + placebo, or placebo only on each day. Dextrin (Nisshin Pharma Inc., Tokyo, Japan) was used as the placebo. All sample capsules were taken with 250 mL warm water at about 25°C. Treatments were allocated using a Latin square design such that the order of treatments was counterbalanced across participants. After each sample was taken, an auditory oddball target detection task (DT) lasting for 5 min each and an arithmetic mental task (AT) lasting for 10 min each were both imposed twice as the psychological stress load. In the DT, participants were required to click the left button of a computer mouse as quickly as possible to target stimuli (a single tone of 2,000 Hz lasting for 0.1 s) that occur infrequently and irregularly within a series of standard stimuli (a single tone of 1,000 Hz lasting for 0.1 s). The AT required participants to add two numbers (each from 1 to 9) that were being displayed on a PC monitor and to enter the answer through the keyboard quickly and accurately. The number and accuracy of the answers to the second AT, which was taken from 26 min to 36 min after each sample intake, were used for data analysis. A cold pressor test (CPT) was taken to establish physical acute stress [20]. Participants were asked to immerse their right hand, past the level of the wrist, for 1 min in a bucket filled with slushy ice water (1.5±0.3C) and then to place the hand on the table nearby with a towel underneath the hand. Arterial pressure in each participant’ s left thumb was recorded continuously by Finometer Pro (FMS, Finapres Measurement Systems, Arnhem, the Netherlands). Simultaneously, skin temperature of the back of the left hand was recorded using a BioAmplifier (Polymate AP1132, TEAC, Tokyo, Japan). The sampling rate was 200 Hz. As baseline data, both the blood pressure and skin temperature were measured for 1 min before the intake. Measurement after mental tasks (AMT) was also made for 1 min at 44 min after the intake of each sample, followed by measurement for 4 min after CPT was started. Baseline data were calculated by averaging the 1 min data before each intake. Differences in blood pressure and skin temperature from the baseline were calculated using the mean value of every 10-s epoch for the above measurements after intake. The first 10-s epoch of the AMT was described as AMT1, and the second, third, fourth, fifth, and sixth 10-s epochs were described as AMT2, AMT3, AMT4, AMT5, and AMT6, respectively. Similarly, CPT1 to CPT6 for the CPT epochs, and RP1 to RP18 for epochs during the 3-min recovering period after the 1 min CPT were named respectively and used for the analysis.
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How many outcome-specific endpoints are evaluated? 1
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (systolic and diastolic)
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List additional health endpoints (separately). 2
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List additional health endpoints (separately).3
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description Arterial pressure in each participant’ s left thumb was recorded continuously by Finometer Pro (FMS, Finapres Measurement Systems, Arnhem, the Netherlands). Simultaneously, skin temperature of the back of the left hand was recorded using a BioAmplifier (Polymate AP1132, TEAC, Tokyo, Japan).
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Placebo vs.100 mg caffeine+placebo
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) L-theanine reduced blood pressure in spontaneously hypertensive rats but not in rats with normal blood pressure [6,7]. Thus it is considerable that L-theanine might act in different ways between people in whom stress increases whose blood pressure in different ways. With this in mind, we divided the participants into two groups after the experiment according to their changes in systolic blood pressure after the mental tasks in the placebo intake condition. The half of participants who showed greater than average changes in blood pressure were sorted into a high-response group and the other half into a low-response group. Differences in blood pressure and skin temperature from the basic control were calculated and used for a repeated-measures ANOVA with group (high-response group and low- response group), treatment (L-theanine, caffeine, and placebo), and epoch (six epochs for AMT, CPT and 18 epochs for CPT). Repeated-measures ANOVA with group and treatment was also applied to the task performance data. A Tukey’ s honestly significant difference (HSD) post hoc test was applied to data groups with significant main effect (P <0.05). Differences in POMS and VAS scores were analyzed using the nonparametric Friedman test to detect differences in treatments.
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What conflicts of interest were reported? "The authors declare that they have no competing interests."
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Refid 23107346
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What were the sources of funding? "This work was supported in part by grants from the Collaboration of Regional Entities for the Advancement of Technological Excellence (CREATE), research funds provided by the Japan Society and Technology Agency (JST), and by a Grant-in-Aid for Scientific Research (B) provided by the Japan Society for the Promotion of Sciences (JSPS) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan."
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