Guarana (Paullinia cupana) extracts are popular in energy drinks, teas, and capsules.

In this study, taking guarana improved mental performance and reduced the mental fatigue associated with tasks requiring a sustained mental effort.

How’d it do that?

First, the details.

• 129 healthy young adults were randomly assigned to take a vitamin/mineral/guarana supplement or placebo drink.
• Participants completed a 10-minute test that included subtracting by 3s and 7s; and a test of sustained attention that required working memory.
• Then, 30 minutes following their drink participants took the test 6 more times.
• Neither the participants nor the researchers knew the treatment given — double-blinded.

And, the results.

• The vitamin/mineral/guarana combination resulted in improved task performance as measured by increased speed and accuracy.
• The increase in mental fatigue associated with testing was attenuated by the supplement.

The bottom line?
The authors concluded that adding guarana to a multivitamin/mineral supplement “can improve cognitive performance and reduce the mental fatigue associated with sustained mental effort.”

The abstract doesn’t reveal the amount of guarana in the test drink. However, according to Wikipedia, the guarana seed contains between 9,000 and 76,000 parts per million of caffeine. Nothing else in guarana appears to be responsible for the results described in this study.

The short duration of the study (1.5 hours) may not provide an accurate picture of the mental fatigue that the participants felt 6, 12, or 24 hours later.

More background on guarana can be found here.

8/17/08 14:40 JR