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Study Title and Description

Caffeine in hot drinks elicits cephalic phase responses involving cardiac activity.



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 Caffeine in hot drinks elicits cephalic phase responses involving cardiac activity.
Author MK McMullen,JM Whitehouse,G Shine,PA Whitton,A Towell,
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)? Caffeine has been reported to stimulate 5 of the 25 bitter taste receptors (hTAS2Rs: 7, 10, 14, 43, 46) located in the human oropharyngeal cavity as well as receptors found in the intestinal STC-1 cells lines. Stimulation of oropharyngeal taste receptors activates neurons located in the rostral nucleus tractus solitaries whereas the stimulation of gut taste receptors activates neurons located in the caudal nucleus tractus solitarius. Consequently, our research group has hypothesised that the stimulation of either oropharyngeal or gut hTAS2Rs by caffeine may elicit reflex autonomic responses involving the cardiovascular system. The impact of caffeine and coffee on the cardiovascular system has been extensively researched and reviewed in the acute period 30 to 120 post-ingestion, but little is known of the more immediate effects of caffeinated drinks in the pre-acute period 0 to 30 min post-ingestion. Coffee containing 130 mg caffeine has been reported to increase heart rate for 30 min post-ingestion. Whereas added-caffeine, in doses of 25 to 200 mg, ingested with decaffeinated coffee/tea decreases heart rate 10 to 30 min post-ingestion. This study aimed to clarify caffeine’s chemosensory impact.
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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) Two participant groups were used and by chance, both were comprised of only women. The control group was selected from our previous study23 which involved a double-blind presentation of caffeine and placebo-control capsules. One participant from the previous study, who had an extreme BMI, was excluded from the present study. The second group, the test group, was recruited specifically for this study. Espresso coffee was chosen as the test form because it is straightforward to produce as a standard serving and is traditionally consumed in small volumes. Regular and decaffeinated ‘‘medium roasted Columbia’’ whole coffee beans were used for testing. A double espresso of circa 67 mL was produced from 16.5 g of beans using an espresso machine. The espresso caffeine content was analysed using HPLC and estimated at 130 mg for regular coffee and <10 mg for decaffeinated coffee. During the production of the individual test beverages, the contents of a capsule containing either cellulose (control) or caffeine (67 or 134 mg) was added to the ground coffee beans. The caffeine conformed to British Pharmacopeia standards. Subsequent HPLC analyses indicated that caffeine was present at the appropriate level in the test beverages. The caffeine amounts of 67 and 134 mg are representative of caffeine levels found in single servings of coffee and tea. A haemodynamic monitoring system (Finometer PRO, Finapres Medical Systems, Amsterdam, The Netherlands) was used. The Finometer records the finger-pulse contour and provides continuous beat-to-beat readings of a number of cardiovascular parameters. An infrared plethysmograph in a finger cuff records (200 Hz) the pulsation of the arterial diameter. Cuff pressure clamps the artery’s unstretched diameter and is attuned so that finger arterial pressure is reflected in the cuff pressure. As well as providing enhanced sensitivity due to the availability of continuous blood pressure readings,30,31 the Finometer also provides cardiovascular measures that are useful for assessing changes of the autonomic system. The measures include heart period, heart rate, contraction force (dp/dt) and brachial systolic and diastolic pressure. Modelflow software, which is integrated into the Finometer system, automatically computes for healthy individuals’ stroke volume, peripheral resistance and arterial compliance as well as the body-surface area adjusted values (Dubois and Dubois formula): ‘‘indexed stroke volume’’ and ‘‘indexed peripheral resistance’’ value.32–36 The indexed values are reported rather than the non-indexed values. Participants attended four test sessions which were conducted at similar times (+/-1 h) of the day so as to minimize diurnal effects. Four coffees were administered in a randomized double-blind design: (1) DC: decaffeinated coffee with control capsule; (2) DC67: decaffeinated coffee with 67 mg caffeine capsule; (3) DC134: decaffeinated coffee with 134 mg caffeine capsule; and (4) RC: regular coffee with control capsule. The caffeine dose for DC67, DC134 and RC was circa 1, 2 and 2 mg/kg respectively. Participants sat for 30 min post-ingestion and test sessions were conducted in silence, with the participants being permitted to read but not write.
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How many outcome-specific endpoints are evaluated? 6
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Heart rate
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List additional health endpoints (separately). 2 Blood pressure
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List additional health endpoints (separately).3 Contraction force (dp/dt)
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List additional health endpoints (separately).4 indexed stroke volume (iSV)
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List additional health endpoints (separately).5 Arterial compliance
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List additional health endpoints (separately).6 Indexed peripheral resistance (iPR)
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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 A haemodynamic monitoring system (Finometer PRO, Finapres Medical Systems, Amsterdam, The Netherlands) was used. An infrared plethysmograph in a finger cuff records (200 Hz) the pulsation of the arterial diameter. Cuff pressure clamps the artery’s unstretched diameter and is attuned so that finger arterial pressure is reflected in the cuff pressure. As well as providing enhanced sensitivity due to the availability of continuous blood pressure readings, the Finometer also provides cardiovascular measures that are useful for assessing changes of the autonomic system. The measures include heart period, heart rate, contraction force (dp/dt) and brachial systolic and diastolic pressure. Modelflow software, which is integrated into the Finometer system, automatically computes for healthy individuals’ stroke volume, peripheral resistance and arterial compliance as well as the body-surface area adjusted values (Dubois and Dubois formula): ‘‘indexed stroke volume’’ and ‘‘indexed peripheral resistance’’ value.
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? Coffee
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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.) Control group of 11 females vs. exposed group of 10 females.
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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) Hypertensives (systolic pressure >140 mm Hg or diastolic pressure >90 mm Hg), smokers, pregnant women and those on prescribed medication were excluded from the study.
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What conflicts of interest were reported? "Potential conflicts of interest: none."
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Refid 22614720
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What were the sources of funding? "Sources of support/funding: no external funding or sponsoring was involved in this study. Caffeine and placebo capsules were generously prepared and donated by Dr Brian Whitton of Poppypac UK."
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Results & Comparisons

No Results found.