Yerba maté (Ilex paraguariensis) is a South American tea which is a rich source of caffeine, theobromine, cinnamate esters, and numerous other bioactive compounds. Yerba maté and extracts of the plant have been shown to have remarkable antioxidant, antibacterial, antimicrobial, stimulant, diuretic, antihypercholesterolaemic, anti-obesity and anticarcinogenic properties. Ilex paraguariensis extract has been shown to reduce the myocardial dysfunction provoked by ischemia and reperfusion by means of a reduction in oxidative damage. An extract of the tea has been shown to improve the cognition of laboratory rats and yerba maté is believed to enhance memory. One study found that postmenopausal women who consumed yerba maté tea daily for at least five years had higher bone mineral density compared with women who did not drink the tea.
Cancer-related effects of drinking yerba maté
Extracts of Ilex paraguariensis have been shown to reduce DNA damage and the incidence of carcinogen-induced esophageal tumors, as well as inhibiting oral cancer cell proliferation in the laboratory. However, drinking the tea itself has been shown to be promote digestive tract cancers in several population studies.
Yerba maté contains relatively high levels of polycyclic aromatic hydrocarbons (PAHs), including known carcinogens. Significant fractions of these compounds are released even if the leaves are infused with cold water. The tea has been shown to be associated with higher risks of cancers of the esophagus, oropharynx, larynx, lung, kidney, and bladder. Although drinking any type of tea at a very high temperature increases the risk of esophageal cancer, the drinking of yerba maté at a very hot temperature does not explain all of the increased risks of cancers of the esophagus, oropharynx, and larynx. This is reason for concern.
On the other hand, a 2016 Uruguay study reported that women with relatively high yerba maté consumption had significantly lower risk of breast cancer than women with low or no yerba mate intake. This was especially true for obese women. A 2017 Brazilian study reported that more than two-thirds of 104 yerba maté samples from three Brazilian states incorporated unacceptably high levels of cadmium, a known breast carcinogen.
Several herbal weight loss formulations and energy drinks containing yerba maté (possibly listed as Ilex paraguariensis or l. paraguariensis on the label) are available in the U.S. market and should also be avoided by those with breast cancer, breast cancer survivors or those known to be at high risk.
Few studies are available concerning this food and breast cancer. Below are links to recent studies.