Guarana berry is sold as a nutritional supplement and marketed to athletes looking to obtain peak performance.

Guarana, or Paullinia cupana, is a plant in the maple family that grows along the Amazon and is common in Brazil. Its seeds — which look oddly similar to eyeballs — are used for a variety of reasons.

It’s been used for centuries as a tea in Guarani culture. The tea is traditionally made by grinding the shelled seeds into a paste and then grating it into hot water and sugar.

Guarana is most commonly used as a stimulant and contains about twice the caffeine of the coffee bean. It also contains theobromine and theophylline, other stimulants that affect the central nervous system.

Can Guarana Boost Your Athletic Performance?

Everyone could use a little boost, whether it’s to get you through Monday morning or the first leg of the Ironman.

Guarana’s edge is in its high caffeine content. Caffeine has been used to boost athletic performance since the times of the gladiators. It’s also one of the most widely used and socially acceptable legal drugs in the world.

Tests on mice showed that guarana increased both their physical and mental strength, along with memory.

Can Guarana Give You a Mental Edge Up?

Tests on humans determined that a 75 mg dose of dried extract could improve task performance and increase attention span for up to six hours. However, researchers also found signs of reduced accuracy.

Other research suggests that adding guarana to a multivitamin can help young adults perform better at mental tasks and fight the mental fatigue associated with long periods of brainwork, like studying for finals.

One study found that guarana is an effective and inexpensive short-term treatment to help fight the fatigue common in women who undergo chemotherapy for breast cancer.

So if you’re have a lot going on at once, it’s scanning the field for the next play or merely picking up dry cleaning with a sick toddler in tow, guarana might be able to give you the boost you need.

Can Guarana Help You Lose Weight?

Stimulants can increase your heart rate and boost your metabolism, which is why they have historically been used to shed weight. While many dietary aids have been removed from the market because they were deemed unsafe, the U.S. Food and Drug Administration considers guarana to be safe in normal doses.

In 2002, researchers studied whether a mixture of guarana, yerba mate, and damiana (all rich in caffeine and other stimulants) could help people lose weight. The researchers found that the mixture resulted in “significant” weight loss after 45 days.

Some Cautions About Guarana

While studies on mice show that using guarana won’t shorten lifespan, it can have some drawbacks.

The side effects of guarana are the same as the side effects of caffeine, namely:

  • possible anxiety
  • restlessness
  • difficulty sleeping

Children and women who are pregnant or breastfeeding should avoid guarana. People with heart conditions and other serious medical conditions should discuss guarana with their doctors before consuming it.