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Clinical Studies on Guarana
In a study reported in The Journal of Human Nutrition Diet, guarana extract
induced weight loss for over 45 days in overweight patients taking a mixed
herbal preparation containing yerbemate, guarana, and damiana (Andersen et al.
2001). Body weight reductions were 11.22 pounds in the guarana group compared to
less than 1 pound in the group receiving placebo for 45 days.
Guarana extract and its fractions decreased platelet aggregation up to 37% of
control values and decreased platelet thromboxane formation from arachidonic
acid up to 78% of control values (Bydlowski et al. 1991). When platelets
hyperaggregate and/or when excess thromboxane formation occurs, this can
initiate an arterial blood clot, which results in a heart attack or ischemic
stroke.
In a 1997 study in rats, guarana increased the physical activity of the rats as
well as increased physical endurance under stress and increased memory with
single doses as well as with chronic doses. Interestingly enough, this study
revealed that whole guarana seed extract performed better and more effectively
than a comparable dosage of caffeine or ginseng extract (Espinola et al. 1997).
Another Brazilian research group has studied the apparent effect of guarana to
increase memory, which is thought to be linked to the essential oils found in
the seed (Galduroz et al. 1996). Its antibacterial properties against
Escherichia coli and Salmonella have been documented as well (da Fonseca et al.
1994).
A 1998 toxicology study with animals has shown that guarana is nontoxic at even
high dosages of up to 2 grams/kg of body weight. This same study demonstrated
the antioxidant properties of guarana, saying: "Guarana showed an
antioxidant effect because, even at low concentrations (1.2 mcg/mL), it
inhibited the process of lipid peroxidation" (Mattei et al. 1998).
A major advantage to taking guarana in an oil base capsule is its relatively
slow release into the body. In a study reported in the journal Pharmacology
Biochemical Behavior in November 1997, a comparison was made of the absorption
of caffeine from coffee, cola, or capsules. Based on saliva caffeine
concentrations, the absorption from capsules was about 40% slower than that of
coffee or colas. These capsules were not oil-based, yet the rate of caffeine
absorption was still significantly slower than coffee or cola (Liguori et al.
1997). |
