How Does Caffeine & Guarana Work?

According to a 2008 article published in Plant Cell Reports, guarana, or Paullinia cupana var. sorbilis, is "a plant native to the central Amazon basin" whose roasted seed extracts have been in medicinal beverages since before the Spanish conquest. Caffeine naturally occurs in guarana at levels around 12 percent in a standard guarana extract. Research has tried to determine whether guarana has effects, and if those effects are unique to elements of guarana extract other than caffeine, which we know is a stimulant.

Guarana's Reputation

These beverages have a reputation as stimulants, aphrodisiacs, tonics, and protectors of the gastrointestinal tract. A peer-reviewed article published in 2004 in the journal Pharmacology, Biochemistry and Behavior addresses this. It explains that guarana extracts added to modern drinks, foods, and dietary and herbal supplements are there because of supposedly stimulating effects.

Risks of Self Administering Marketed Paramedicinal Products

There is a reported a case of a 30-year old woman whose permanent use of guarana, occasionally with painkillers, led to kidney failure and the suspension of urination for 48 hours. Authors who published the case in a Hungarian medical journal in 2007 did so to draw attention to problems that can occur when patients self-administer hyper-marketed supplements on their own or in conjunction with regular pharmaceutical products.

Remember, herbal supplements don't have to pass the rigorous approval process that regular medicines do. With comparatively less research, these supplements can have unknown impacts as well as little-understood interactions with your other medications. Talk with your family doctor before adding a supplement or herbal product to your daily diet, and remember that in all things moderation is the key.

Increased Physical Capacity in Lab Rats

A 1997 study on lab animals found that with small doses, .3mg/ml of guarana, the mice and rats showed a significant increase in physical capacity when subjected to stressful situations after dosing for 100 and 200 days. Researchers did not find this effect in mice treated with caffeine solution of .1 mg/ml. These results would appear to show that guarana over time can increase your physical endurance. But with different concentrations of the stimulants, or with additional repetitions of the experiment, different outcomes could have occurred. And something to bear in mind is humans are very different from lab rats.

Memory Benefits in Lab Rats

The 1997 study dosing lab rats with small single or chronic doses of guarana also found that the treated mice were partially able to resist the amnesic effects of scopolamine, a drug that completely blocks the formation of memories. Confirmation of definite impacts will need more research, but these results are promising.

Improved Cognitive Performance

The more recent study -- published in late 2004 in the journal Pharmacology, Biochemistry, and Behavior -- also found that human volunteers had improved cognitive performance following administration of guarana. Twenty-eight volunteers between the ages of 18 and 24 participated in the study, which assessed cognitive performance and subjective mood. Researches noted some evidence of improved performance on "attention" tasks, but there was also evidence of reduced accuracy on those test exercises.

Researchers also saw a significant improvement in performance of serial subtraction tasks in conjunction with guarana doses. According to the study's authors, these results provided the first demonstration of the psychoactive effects of guarana. But remember, the sample size was small, just 28 volunteers, so the findings need more research.