Guayusa tea is made from the leaves of the Amazonian tree, Ilex guayusa. The guayusa tree grows predominantly in Ecuador but can also be found in the Amazonian regions of Peru and Colombia. A cup of guayusa tea has about as much caffeine as a cup of brewed coffee, and indigenous Ecuadorians have traditionally cultivated the guayusa tree to enjoy the stimulating tea made from its leaves. Guayusa tea is marketed as an energy drink high in antioxidants. It’s also reported to have a smoother taste than high-tannin teas like green and black teas, which are made from an unrelated plant, Cammelia sinensis.
In one animal study, diabetic mice had better blood sugar control after ingesting an extract from guayusa. Although this doesn’t prove that guayusa has an anti-diabetic effect in people, the fact that other caffeinated beverages like coffee, mate, and green and black teas have all been found to have a positive effect on sugar metabolism and diabetes risk adds weight to the possibility.
Source: Journal of Ethnopharmacology