Just when you thought you had found the biggest jolt you could get from a beverage in espresso, along comes guarana. If carbonated energy boosters don’t do much for you, try one of the new coffee-flavored drinks made from the berries of this herb. But be cautious: Guarana is substantially stronger than caffeine and is associated with serious adverse effects that range from sleeplessness to seizures.

Background

Guarana, or Paullinia cupana, is native to South America.This vining shrub sports large divided leaves and clusters of yellow flowers that produce brownish-red berries, each of which holds a single seed about the size of a coffee bean.1 These seeds contain guaranine, a substance so chemically similar to caffeine that the terms have been used interchangeably.2

After the seeds are harvested and washed, they are roasted for six hours. Once dry, they are lightly crushed to remove the outer shell, pounded into a fine powder, and combined with water to make a dough that is allowed to harden for shipping. Also known as Brazilian cocoa or guarana bread, this hardened dough is typically grated, dissolved in hot water with sugar, and consumed as a drink.3

The amount of guaranine in this beverage is much greater than the amount of caffeine in coffee beans.4 A cup of coffee contains, at most, 130 mg of caffeine. A cup of some of the stronger guarana-based syrups made from dissolved bricks contains as much as 350 mg of caffeine.1

In the United States, the caffeine content must be listed on the labels of products to which caffeine has been added, but no similar regulation applies to products like guarana where caffeine or guaranine occurs naturally.

Research

The most obvious use for guarana is as a stimulant. Research has verified a predictable level of cognitive enhancement with modest consumption, as it has with caffeine and other stimulants.

A British study concluded that lower doses of guarana improved memory, mood, and alertness. The Northumbria University team of scientists used a computerized test battery to monitor human responses to four dose levels (37.5 mg, 75 mg, 150 mg, and 300 mg) vs. placebo. They found that the two lowest doses produced more positive cognitive effects than the higher doses.4

Similar test results were reported when a research team at Universidade Federal da Paraíba in Brazil applied the same protocol to mice and rats. The animals were given graduated doses of guarana concentrate and
tested for physical endurance and memory in a maze. Lower doses produced positive effects while higher doses yielded early signs of caffeine-related toxicity.5

Like many high-caffeine products, guarana beverages have been touted for promoting weight loss. Another Brazilian study verified that guarana supplementation increased fat metabolism in rats, but it also confirmed the effect was due solely to the plant’s caffeine content.6

In the future, guarana may be used as a natural food preservative. Seed extracts have demonstrated strong antimicrobial and antioxidant properties against food-borne fungi and health-damaging bacteria.7