Yerba mate is an herbal product derived from the leaves of the Ilex paraguariensis tree. Argentina, Brazil, Paraguay, and Uruguay are the largest producers and consumers of yerba mate, but consumption around the globe is increasing.^[1] Yerba mate is generally consumed as a tea and is rich in many biologically active compounds with varying health-promoting properties. These include caffeine, theobromine, chlorogenic acid, and various other flavonoids, xanthines, cinnamic acids, saponins, vitamins (e.g., vitamin C, thiamine, pyridoxine, riboflavin) and minerals (e.g., potassium, calcium, magnesium).^[2][1]

Yerba mate tea is commonly used for its stimulant properties, similar to coffee or other teas. The amount of caffeine in yerba mate can vary greatly (11 to 57 milligrams of caffeine per 100 mL) depending on the type of leaves used and how the beverage is prepared.^[2] Caffeine can reduce drowsiness, increase alertness, and improve some aspects of cognition,^[3] but research on yerba mate hasn’t specifically assessed these outcomes.

Yerba mate is rich in antioxidant and anti-inflammatory compounds. Regular consumption has been reported to improve markers of FAQ:what-is-oxidative-stress — the most consistent finding being increased levels of glutathione — in a variety of populations.^{[4][5][6][7][8][9]}

Yerba mate may positively affect metabolic health, including increased fat oxidation during exercise or at rest^{[10][11][12][13]} and small (likely clinically insignificant) reductions in body fat in people with overweight or obesity.^[14][15][16] Some research has also reported decreases in LDL cholesterol in people with dyslipidemia^[17][6][18] and reductions in HbA1c and blood glucose in people with type 2 diabetes;^[19][8] however, this research should be considered preliminary. While appetite suppression has been reported occasionally,^[11][7] this is not consistently found.^[6][19]

Despite widespread consumption of yerba mate (particularly in South America), clinical research examining its health effects remains limited, and the overall evidence base is weak. Many studies could be prone to bias due to the lack of a control group, small sample sizes, being industry-funded, and being of poor methodological quality in general.

Consumption of yerba mate tea is associated with an increased risk of cancers of the upper digestive tract (i.e., the mouth, esophagus, larynx, and pharynx), most notably when consuming more than one liter (about 4 cups) of yerba mate daily.^[20][21] Associations between yerba mate consumption and bladder and lung cancers have also been reported.^[22][23] This could be due to the presence of carcinogenic compounds (e.g., polycyclic aromatic hydrocarbons) produced during the processing of yerba mate leaves, as well as the thermal damage caused to the upper digestive tract when consuming yerba mate hot.^[20][24]

In general, yerba mate is usually tolerated well. Side effects are uncommon, but nausea, insomnia, and irritation of the lining of the mouth or stomach have been reported.^[18]

Yerba mate contains an abundance of bioactive compounds that could act both independently and synergistically to produce various biological effects. However, most mechanisms are theoretical, and more research is needed to better understand how yerba mate works.

Yerba mate's stimulant properties are mostly attributed to its caffeine content. On average, the content of caffeine in yerba mate is less than coffee, but it can be similar depending on brewing conditions.^[2][25]

The xanthines in yerba mate (e.g., caffeine, theophylline, and theobromine) are also suggested to be responsible for increasing fat oxidation and thermogenesis.^[26] This, combined with the regulation of genes involved in adipogenesis (the synthesis of new fat cells) and the increased production of glucagon-like peptide 1 (GLP-1), could contribute to the proposed antiobesity effect of yerba mate.^[27][28] Despite this, clinical trials have generally reported negligible weight loss effects.^[14][15][16]

Yerba mate is rich in polyphenols, such as chlorogenic acid and caffeic acid, that have antioxidant activity and may help protect the body from oxidative stress. These compounds can directly scavenge free radicals while also enhancing the body’s own antioxidant defense mechanisms.^[25]

The lipid-lowering effects of yerba mate have been proposed to be due to the reduced absorption of fats^[29] and the regulation of lipid metabolism.^[1] Theoretically, yerba mate might also reduce glucose absorption^[30] and enhance glucose uptake by cells in the body, providing a blood-glucose-lowering effect.^[31][32] Increased levels of GLP-1 may further support blood glucose regulation.^[28]