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Guayusa extract is a caffeinated tea leaf unique blend of antioxidants and caffeine. It is marketed as an ingredient that can help support energy and performance with potential health-related benefits. It has also been indicated as being as safe as any other existing teas (i.e., green tea). However, no studies have previous studied the dose-response effects of guayusa extract for supporting cognitive function, mood, metabolism, nor its effects on resting heart rate, blood pressure, and electrocardiogram characteristics.
Guayusa extract is a caffeinated Amazonian 'super-leaf' belonging to the holly species that contains a unique blend of polyphenol antioxidants and caffeine (~20% caffeine, 30% chlorogenic acids, 5% catechins). It is also remarkably low in tannins which are responsible for the bitter taste found in most teas - giving it a sweet flavor profile. As such, it is marketed as an ingredient that can help support energy and performance (e.g., via caffeine content) with potential health-related benefits due to its antioxidant properties. Indeed, ingredients such as these are often consumed by individuals prior to exercise in order to help improve neurocognitive performance, mood, or otherwise to support health-related goals such as metabolism. Whereas several studies have suggested that caffeine and chlorogenic acid consumption may improve performance, mood, and concentration, and some evidence in animals have linked catechin consumption to improved health outcomes, no studies have previous studied whether guayusa extract supplementation helps to support these, nor has the dose-effectiveness been tested, in humans.
In this study, the effects of acute dietary supplementation with two different doses of botanical organic guayusa extract on neurocognitive/motor-cognitive performance, mood, focus, and jitteriness, resting metabolism, and resting heart rate, blood pressure, and electrocardiogram characteristics will be examined.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Moderate-Dose Guayusa Extract | Experimental | Acute, single dose of 600 mg Organic Guayusa Extract |
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| High-Dose Guayusa Extract | Experimental | Acute, single dose of 1200 mg Organic Guayusa Extract |
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| Placebo | Placebo Comparator | Acute, single dose of Placebo (dextrose) |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Acute Moderate-Dose Guayusa Extract Supplementation | Dietary Supplement | Participants will consume two vegan capsules with one capsule containing 600 mg AmaTea® and 1 containing 600 mg dextrose. |
| Measure | Description | Time Frame |
|---|---|---|
| Mood | Calculated as Total Mood Disturbance (arbitrary units) using the Profile of Mood States Short Form Questionnaire. | 90-minutes Post-supplementation |
| Psychomotor Speed | How well participant perceived, attends, responds to visual-perceptive information, and performs motor speed and fine motor coordination. Calculated as the sum of finger taps in finger tapping test and correct responses in the symbol digit coding test. | 60-minutes Post-supplementation |
| Executive Function | How well participant recognized rules, categories, and manages or navigates rapid decisions making. Calculated as the differences between Shifting Attention Test Correct Responses and Errors. | 60-minutes Post-supplementation |
| Measure | Description | Time Frame |
|---|---|---|
| Jitteriness | Participants will describe how jittery they feel after supplemention using a 0-100 mm visual analog scale. | 90-minutes Post-supplementation |
| Focus | Participants will describe how focused they feel after supplemention using a 0-100 mm visual analog scale. |
| Measure | Description | Time Frame |
|---|---|---|
| Vigor | Vigor will be quantified using the Profile of Mood State Short Form Questionnaire. | 90-minutes Post-supplementation |
| Tension | Tension will be quantified using the Profile of Mood State Short Form Questionnaire. |
Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Integrative Laboratory of Applied Physiology and Lifestyle Medicine | Iowa City | Iowa | 52242 | United States |
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Randomized, placebo-controlled, double-blind, crossover study
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| Acute High-Dose Guayusa Extract Supplementation | Dietary Supplement | Participants will consume two vegan capsules with each capsule containing 600 mg AmaTea® (1200 mg total). |
|
| Placebo | Dietary Supplement | Participants will consume two vegan capsules with each capsule containing 600 mg dextrose (1200 mg total). |
|
| 90-minutes Post-supplementation |
| Energy | Participants will describe how energetic they feel after supplemention using a 0-100 mm visual analog scale. | 90-minutes Post-supplementation |
| Resting Metabolic Rate | Resting metabolic rate (kcal/min) will be quantified from resting, fasted analyses of pulmonary gas exchange. | 50 minutes post-supplementation |
| Resting Fat Oxidation | Resting fat oxidation (g/min) will be quantified from resting, fasted analyses of pulmonary gas exchange. | 50 minutes post-supplementation |
| Resting Heart Rate | Heart rate (bpm) will be quantified from a standard 12-lead ECG | -10 minutes before supplementation, 40 minutes post-supplementation |
| Resting Blood Pressure | Systolic, diastolic, and pulse pressures (mmHg) will be quantified from brachial artery via automated sphygmomanometer. | -10 minutes before supplementation, 40 minutes post-supplementation |
| QTc Interval | QTc Interval (ms) will be quantified from a standard 12-lead ECG | -10 minutes before supplementation, 40 minutes post-supplementation |
| Motor-Cognitive Reaction Time | Motor-cognitive reaction times (ms) will be quantified from motor cognitive (reactionary hop) tests | 100-minutes Post-supplementation |
| Sustained Attention | How well a subject can direct and focus cognitive activity on specific stimuli. Derived from performance on the 4-part continuous performance task test. | 60-minutes Post-supplementation |
| Working Memory | How well a subject can perceive and attend to symbols using short-term memory processes. | 60-minutes Post-supplementation |
| Cognitive Flexibility | How well subject is able to adapt to rapidly changing and increasingly complex set of directions and/or to manipulate the information. Assessed from the Shifting Attention Task and Stoop Test as the Shifting Attention Task Correct Responses - Shifting Attention Task Incorrect Responses and Stroop Commission Errors. | 60-minutes Post-supplementation |
| 90-minutes Post-supplementation |
| Fatigue | Fatigue will be quantified using the Profile of Mood State Short Form Questionnaire. | 90-minutes Post-supplementation |
| Anger | Anger will be quantified using the Profile of Mood State Short Form Questionnaire. | 90-minutes Post-supplementation |
| Confusion | Confusion will be quantified using the Profile of Mood State Short Form Questionnaire. | 90-minutes Post-supplementation |
| Stress | Stress will be quantified using the Profile of Mood State Short Form Questionnaire. | 90-minutes Post-supplementation |
| Composite Memory | How well subject can recognize, remember, and retrieve words and geometric figures. Assessed as a composite performance indicator during the Verbal Memory and Visual Memory Tests. | 60-minutes Post-supplementation |
| Reaction Time | How quickly the subject can react, in milliseconds, to a simple and increasingly complex direction set. | 60-minutes Post-supplementation |
| Complex Attention | Ability to track and respond to a variety of stimuli over lengthy periods of time and/or perform mental tasks requiring vigilance quickly and accurately. | 60-minutes Post-supplementation |
| Reasoning | How well is subject able to recognize, reason and respond to non-verbal visual-abstract stimuli. Assessed from the non-verbal reasoning test as the difference between the number of correct responses and commission errors. | 60-minutes Post-supplementation |