Q. Are there actually health benefits from drinking yerba mat tea? What is yerba mat, anyway?
A. Diane L. McKay, PhD, an assistant professor at Tufts Friedman School, replies: Yerba mat tea is made with the dried leaves of Ilex paraguariensis, a subtropical evergreen tree native to South America. Fresh mat leaves undergo several stages of processing including blanching, drying and aging prior to packaging. During blanching, the mat leaves are flash-heated over an open flame. The leaves are then dried very slowly, often using wood smoke, and aged for up to 12 months for flavor development. The name mat is derived from the Quechua word mat meaning a cup or vessel used for drinking. Other names for beverages made with I. paraguariensis include Jesuits tea, Paraguayan tea, cimarr?n and chimarra. In the United States, mat is commercially packed in individual tea bags or as a tea concentrate.
Mat has long been used by the indigenous peoples of South America, especially the Guarani Indians. In folk medicine, mat is used as a central nervous system stimulant, diuretic and anti-rheumatic. The German Commission E (a scientific advisory board to the equivalent of the FDA) approved the internal use of mat for mental and physical fatigue.
Although in vitro and animal studies suggest a potential anti-carcinogenic effect of mat, the available epidemiological evidence does not. Several case control studies conducted in South America reported an association between the consumption of yerba mat tea and an increased risk of oral, laryngeal, esophageal, lung, kidney and bladder cancers.
These negative effects may be due to the way the tea leaves are processed in South America. That is, during the drying process there is some introduction of carcinogens from the smoke used; the carcinogens are called polycyclic aromatic hydrocarbons.
Few clinical trials of mat have been published, and none have reported any statistically significant findings that can be attributed to mat consumption.
Bottom line, yerba mat is an effective pick-me-up (due to the presence of naturally occurring stimulants), but the jury is still out on whether any of the potential benefits suggested by cell culture or animal studies will pan out in humans.