Herb library · Herb · Ilex paraguariensis
Yerba mate
A South American holly whose leaves make maté, a caffeinated everyday drink, also sold for energy and weight loss. Trials suggest a possible small effect on blood sugar and none on cholesterol. Maté is traditionally drunk very hot, which WHO's cancer agency links to esophageal cancer.
Serious warning
WHO's cancer agency (IARC) classifies drinking very hot beverages, above 65 °C, as probably causing esophageal cancer; maté is traditionally drunk at about 70 °C. IARC found no conclusive evidence of cancer from maté drunk at temperatures that are not very hot.
Traditional use
Maté is an infusion of the dried leaves of Ilex paraguariensis, drunk mainly in South America and to a lesser extent in the Middle East, Europe and North America. It is traditionally drunk very hot, at about 70 °C, and also warm or cold (IARC). Supplements of the extract are sold for energy, weight loss, cholesterol and blood sugar.
What studies show
- Limited
Blood sugar: a 2025 meta-analysis of 13 randomized trials found that in people with prediabetes, yerba mate lowered after-meal blood sugar and a measure of insulin resistance, from only two studies each; the authors say more research is needed. It did not change fasting glucose or fasting insulin.
- Limited· shows no benefit
Cholesterol and triglycerides: a 2022 meta-analysis found no difference in total, LDL or HDL cholesterol or triglycerides between yerba mate and control groups, and the 2025 meta-analysis agreed. Both note the studies were small.
- Limited· shows no benefit
Weight: the 2025 meta-analysis found no significant effect on body mass index or waist size.
- Limited
Iron: in a small randomized crossover trial in people with hereditary hemochromatosis, drinking a yerba mate infusion with a meal reduced how much iron was absorbed from it.
Be careful of
Cautions
- NoteLet it cool before drinking. A 2018 meta-analysis of 15 studies linked maté drinking with higher odds of mouth, throat, esophagus and larynx cancer, with more risk above a liter a day; unlike IARC, it found the link at all temperatures.
- NoteMaté leaves are often dried with smoke, and commercial samples often carry high levels of cancer-causing polycyclic aromatic hydrocarbons (PAHs); how much passes into the drink varies widely (a 2019 review).
- NoteSide effects reported in trials included mouth irritation, trouble sleeping, a fast heartbeat, chest pain (angina), headache and stomach upset.
- ConditionIn a small trial, yerba mate drunk with a meal reduced how much iron the body absorbed from it. If you have low iron, ask a clinician about timing.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“This tree yields Paraguay tea or Yerba maté, St. Bartholomew's tea or Jesuit's tea, which is consumed in immense quantities in South America in place of Chinese tea. Its effects are said to more nearly resemble coca than tea.”
“The plant grows along water courses, and from December to August collecting parties gather the leaves which, after a preparatory torrification to enhance their aroma, are powdered and enter into commerce and are sold to be prepared by infusion like common tea.”
Sources
- IARC Monographs evaluate drinking coffee, maté, and very hot beverages (Press release No. 244, 2016) (opens in a new tab) · WHO · read September 25, 2026
- Yerba Maté and its impact on glycemic control and metabolic health: a systematic review and meta-analysis (Front Endocrinol, 2025) (opens in a new tab) · NIH · read September 25, 2026
- Effect of Yerba Mate (Ilex paraguariensis) on Lipid Levels: A Systematic Review and Meta-Analysis (Plant Foods Hum Nutr, 2022) (opens in a new tab) · NIH · read September 25, 2026
- Maté consumption association with upper aerodigestive tract cancers: A systematic review and meta-analysis (Oral Oncol, 2018) (opens in a new tab) · NIH · read September 25, 2026
- Polycyclic aromatic hydrocarbons as a potential source of carcinogenicity of mate (2019) (opens in a new tab) · NIH · read September 25, 2026
- Ilex paraguariensis (A. St.-Hil.) leaf infusion decreases iron absorption in patients with hereditary hemochromatosis: a randomized controlled crossover study (Food Funct, 2021) (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.