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Guayusa (Ilex guayusa) is a holly tree native to the Amazon rainforest.

People have harvested this tree’s leaves since ancient times due to their perceived health benefits, including antioxidant and anti-inflammatory properties (1).

Today, guayusa beverages like tea are becoming increasingly popular. Still, you may wonder whether its benefits are backed by science — and whether it has any side effects.

This article examines the uses, benefits, and side effects of guayusa.

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What is guayusa? 

Guayusa trees can grow 19–98 feet (6–30 meters) tall and produce bright green, oblong leaves.

Although found throughout the Amazon rainforest, this species is most widely cultivated in Ecuador (2).

Traditionally, its leaves are picked, dried, and brewed to make herbal tea.

Today, it’s also sold as a powder and extract — and added to products like energy drinks and commercial teas.

Guayusa contains significant concentrations of caffeine and is a rich source of antioxidants and other beneficial plant compounds (1).

Guayusa is native to the Amazon rainforest and harvested primarily in Ecuador. Its leaves are typically brewed to make tea and touted for their caffeine and antioxidant content.

Potential benefits and uses of guayusa 

Guayusa may provide several health benefits, though research on this is limited.

May improve mood and concentration

Guayusa packs an impressive punch of caffeine, a known stimulant.

In fact, it offers similar amounts of caffeine as regular coffee (3).

In addition, it contains theobromine, an alkaloid that’s structurally similar to caffeine. Theobromine is also found in foods like chocolate and cocoa powder (4).

In combination, caffeine and theobromine have been shown to boost mood, alertness, and concentration (5).

One study in 20 healthy adults found that a mixture of caffeine (19 mg) and theobromine (250 mg) may improve short-term brain function (6).

Rich in antioxidants

Studies reveal that guayusa boasts several antioxidants (2, 7, 8).

These substances reduce oxidative stress by combating free radicals, which are unstable molecules in your body. They may help decrease your risk of several chronic diseases (9).

Guayusa is particularly rich in a group of polyphenol antioxidants known as catechins. These may protect against inflammation, heart disease, cancer, and type 2 diabetes (10, 11, 12, 13).

Notably, animal studies have linked catechins in tea to decreased cholesterol levels (3).

Still, more research needs to be done on guayusa’s specific compounds and their effects on human health.

May stabilize blood sugar

You may experience high blood sugar if your body is unable to efficiently transport sugar from your blood into your cells. If left untreated, this condition can eventually lead to type 2 diabetes.

While the exact mechanism is uncertain, guayusa may help lower blood sugar.

In a 28-day study in nondiabetic mice, guayusa supplements were shown to significantly decrease blood sugar levels, suppress appetite, and reduce body weight (14).

The current research is very limited, however, and its results don’t necessarily apply to humans. Further human studies are needed.

May aid weight loss

Guayusa may promote weight loss due to its high caffeine content.

Caffeine is a natural stimulant that helps boost metabolism, increasing the number of calories your body burns. Studies also reveal that it decreases appetite (15, 16, 17).

However, many of these benefits may be only short term, because caffeine’s effects appear to lessen over time (18).

What’s more, most studies use extremely high doses that you wouldn’t reach with a mug or two of guayusa tea.

Ultimately, more research is needed on long-term, low dose caffeine intake.

Guayusa is rich in antioxidants and caffeine. It may provide multiple health benefits, including improved concentration, blood sugar regulation, and weight loss.

Side effects of drinking too much guayusa 

In general, guayusa is very safe. In moderation, it isn’t linked to any adverse effects (8).

Excessive doses of caffeine may cause symptoms like restlessness, anxiety, and insomnia. Yet, despite its caffeine content, guayusa doesn’t appear to cause the jitteriness associated with other caffeinated beverages, such as coffee (19).

Still, like many teas, guayusa harbors tannins — compounds that may interfere with iron absorption and trigger nausea, especially if consumed on an empty stomach (20, 21, 22).

Tannins aren’t likely to harm your health in the low amounts found in tea, but people with iron deficiency may want to limit their intake.

Guayusa is largely considered safe and has very few side effects. Due to its tannin content, those with iron deficiency may need to limit their intake.

How to make guayusa tea 

Guayusa tea is incredibly easy to make. You can enjoy it warm or serve it chilled over ice.

Nonetheless, due to its caffeine content, you may not want to drink it before bed.

You’re more likely to find guayusa sold in loose-leaf form, although tea bags are available as well. You can buy it in specialty stores or online.

To brew it:

Keep in mind that powders and extracts exist as well. These can be added to foods like smoothies, oatmeal, and yogurt bowls.

Guayusa tea is easy to prepare and add to your diet. It can be served warm or chilled.

The bottom line

Guayusa leaves contain various beneficial compounds linked to potential health benefits.

This Amazonian plant is rich in antioxidants and caffeine that may promote weight loss, blood sugar regulation, and improved mood and alertness.

Its tea is safe to drink and serves as an excellent alternative to coffee. To try it, steep loose leaves in boiling water and strain before drinking.