In harvesting, mate gatherers called tarrafeiros or yebateros travel through the jungle searching for a stand of trees called a mancha. Harvesting is done between May and October, when the tree is in full leaf, and leaves are picked from the same tree only every third year thus protecting the tree for the ensuing crop. Yerba mate has been used medicinally as a diuretic, tonic, and a central nervous system stimulant. Yerba mate's tonic effect on the body helps to regulate sleep cycles and reduce fatigue. Mate is used to reduce appetite, invigorate the body, and affects the muscles by reducing fatigue.
Sterols resembling ergosterol and cholesterol are also present in yerba mate.
In addition, Yerba Mate is a rich source of minerals and 15 amino acids are present in the leaves. This study suggests the presence of potentially useful antidiabetic agents in Mate. Brazilian researchers in 1998 discovered a vasodilatory effect of a Mate extract. The antioxidant properties demonstrated clinically by Yerba Mate were reported in three clinical studies demonstrating its high antioxidant values linked to rapid absorption of known antioxidant phytochemicals found in Mate leaves. Research performed in 1999 by a group of scientists in Switzerland on healthy human subjects indicated that yerba mate may be beneficial as a weight loss aid.