The Effects of Guarana
The positive effects of Guarana on cognitive functions and mental fatigue is well documented in various studies involving lab animals, and human subjects. These studies have found Guarana to help improve cognitive performance, while reducing mental fatigue. It has also been found to help memory performance, and improve mood and alertness.
In a UK study conducted at Northumbria University in Newcastle upon Tyne, 129 healthy young adults aged 18 to 24 years old participated in a guarana extract study. The double-blind, randomised, placebo-controlled, parallel groups study assessed the acute effects of a vitamin, mineral, and guaraná supplement. In this study, the participants completed a set of cognitive tasks to measure mental performance. It was found that the group consuming the Guarana supplement had improved task performance compared to the placebo group. The study found that the Guarana supplement attenuated the mental fatigue, and thus demonstrates Guarana's cognition enhancing properties, and is able to reduce mental fatigue associated with sustained mental effort. [3]
In another UK study performed also at Northumbria University, a double-blind, counterbalanced, placebo-controlled study assessed the acute mood and cognitive effects throughout the day of four different doses of a standardized guaraná extract. The four doses were 37.5mg, 75mg, 150mg and 300 mg. The 26 human subjects performed various mental and cognitive exercises. The study found that Guarana increased the alertness and improved the mood ratings of the participants. It also improved the secondary memory performance of the subjects. [4] The research found that the two lower doses (37.5mg and 75mg) produced more positive cognitive effects than the two higher doses (150mg and 300mg).
While I found many studies with overwhelming evidence of Guarana's beneficial effect on cognition and mental alertness, I also did come across one study where the effects of Guarana was not apparent in a group of elderly volunteers. This was a Brazilian study assessing the effects of long term administration of guarana on cognition in 45 normal, healthy, elderly volunteers. However the results of this double blind study could not determine any significant cognitive alterations in these volunteers. [5]
Guarana and Weight Loss Benefits
Aside from its popular use as an energy drink / supplement, Guarana is also widely used in numerous fat burners and diet pills. Guarana contains caffeine, which is a stimulant that's known to have weight loss benefits. Because of this, it is a common ingredient you will find in weight loss supplements. Studies performed on common weight loss ingredient mixtures including Yerba Mate, Guarana, Damiana, and green tea have consistently found a positive correlation between using these ingredients and achieving weight loss.
Weight loss and delayed gastric emptying following a South American herbal preparation in overweight patients.
Andersen T, Fogh J.
Department of Ultrasound, Medical Center Charlottenlund, Trunnevangen 4A, DK 2920, Charlottenlund, Denmark.
This study was designed to determine the effects of a herbal preparation containing Yerba Maté, Guarana, and Damiana (YGD) on weight loss and gastric emptying. Gastric emptying was observed using ultrasound scanning in seven healthy volunteers following YGD and placebo capsules taken with 420 mL apple juice. Body weight was observed before and after 10 days of treatment with three YGD or placebo capsules for 10 days in 44 healthy overweight patients. Forty-seven healthy overweight patients entered a double-blind placebo-controlled parallel trial of three capsules of YGD capsules before each main meal for 45 days compared with three placebo capsules on body weight. Body weight was monitored in 22 patients who continued the YGD treatment for 12 months.
The study found that the Guarana herbal mixture prolonged gastric emptying time compared to the placebo group. They also recorded body weight reduction of 0.8kg for the YGD group compared to 0.3kg for the placebo group for the 10 day trial. For the 45 day trial, they found even greater weight loss where the YGD group lost on average 5.1kg compared to the 0.3kg of the placebo group. They concluded that the mixture of Yerba Mate, Guarana, and Damiana mixture capsules significantly delayed gastric emptying, reduced the time to perceived gastric fullness and induced significant weight loss over 45 days in overweight patients. [6]
In another 12 week study, 105 subjects were giving either a placebo or a weight loss formula consisting of Asparagus, Green tea, Black tea, Guarana, Mate and Kidney beans. The results of this study found a significant change in the body composition improvement in the weight loss formula group compared to the placebo group. There was greater body fat loss and a significant change in body composition. However, the study also notes that there was not a significant change in weight or BMI. [7]
Side Effects of Guarana Extract
In the United States, guarana has the status of being generally recognized as safe (GRAS). [2] However, despite this, there are some potential side effects of Guarana because it contains the stimulant caffeine. Some possible Guarana side effects include:
- jitteriness and anxiety
- trouble falling asleep
- increased blood pressure
- shortness of breath
- headaches
- upset stomach
- nausea
- increased urination frequency
These side effects of Guarana will vary from individual to individual. Some individuals who tolerate stimulants well may not notice any side effects, while others will experience these side effects at varying degrees. In a study performed at the Nova Southeastern University in Florida, a study was undertaking to assess the safety issues associated with commercially available energy drinks. Their research involved Red Bull, caffeine, glucose, ginseng, guarana, taurine, and bitter orange. Based on their study, most energy drinks contain natural products such as guarana, ginseng, and taurine with as much as 80 to 300mg of caffeine per average 8 oz serving.
Based on their research results, they stated that "no reports were identified of negative effects associated with taurine, ginseng, and guarana used in the amounts found in most energy drinks." However, "the commonly reported adverse effects seen with caffeine in the quantities present in most energy drinks are insomnia, nervousness, and headache." [8] Based on their study results, they concluded that the amounts of guarana, taurine, and ginseng contained in various popular energy drinks are much below the required amounts to deliver either therapeutic benefits or adverse side effects.
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