The biggest issue regarding yerba mate:
Here is a copy of a page from the Mayo Clinic web site that has been having a negative effect on our business because it is coming up on the first page on Google search for yerba mate.
Yerba mate: Is it safe to drink?
A friend suggested that I try yerba mate tea to boost my energy. What is yerba mate? Is it safe?
Answer from Katherine Zeratsky, R.D., L.D.
"Some studies indicate that people who drink large amounts of yerba mate over prolonged periods may be at increased risk of various types of cancer, including cancer of the mouth, esophagus and lungs. Smoking in combination with yerba mate seems to greatly increase the cancer risk. However, occasional use of yerba mate probably poses no serious risks for healthy adults. As always, check with your doctor before using any herbal product."
Here are the facts from an excerpt from the JOURNAL OF FOOD SCIENCE—Vol. 72, Nr. 9, 2007Yerba Mate Tea (Ilex paraguariensis):
A Comprehensive Review on Chemistry, Health
Implications, and Technological Considerations
C.I. HECK AND E.G. DEMEJIA
"Cancer prevention. In vitro and animal experiments have shown a protective effect of Mate against cancer. Several studies have been conducted on the anticancer properties of Mate tea and comparisons have been made with other teas such as green tea, believed to have high anticancer potential (Yamamoto and others 1997)."
"Epidemiological studies.There has been a growing concern over the fact that there are some epidemiological studies that suggest an association between Mate consumption and increased risk of developing certain cancers, namely, esophageal, oral, lung, bladder, renal, and other cancers of the head and neck (Pintos and others 1994; De Stefani and others 1996, 1998; Goldenberg and others 2003; Bates and others 2007). These incidences have been highly correlated to regions in which heavy Mate consumption persists, portions of Brazil and Uruguay. However, it is also recognized that other habitual factors may play a role, such as smoking and alcohol consumption, which are strongly associated with the culture of these regions.Goldenberg (2002) and Goldenberg and others (2003, 2004) report of epidemiological studies showing increased rates of squamous cell carcinoma with increased Mate consumption even when other confounding factors such as smoking were present. The results of these studies indicate that consuming more than 1 L of Mate a day can increase the risk for head and neck cancer by 3 to 5 times, as well as an apparent association to lung cancer (Vassallo and others 1985; De Stefani and others 1996; Sewram and others 2003). It was also reported that consuming strong and very hot tea can increase the risk for oral cancer. Consuming other hot beverages, coffee and green tea, also increased this risk by 2 to 4 times. Thus, the measured risk of oral cancer may be due to thermal injury (Rolon and others 1995; Castellsague and others 2000).With respect to bladder cancer, again epidemiological studies by the same leading authors (De Stefani and others 1991) conducted in Uruguay showed that a relationship between Mate and bladder cancer was found when associated with smoking and to some degree in nonsmokers as well, though less defined. In the same study, it was also shown that consumers of black tea and coffee had an increased risk of bladder cancer. An epidemiological study conducted in Argentina showed an increase risk of bladder cancer in Mate drinkers and smokers but not in nonsmokers (Bates and others 2007). Whether this increased risk of bladder cancer is due solely to Mate alone, smoking alone, a combination of both, or solely another cause is unclear. It should also be noted that the case studies of Mate consumption and increased cancer incidence also include individuals that consume black tobacco and alcohol, namely, wine. De Stefani and others (1988) stated that there is a correlation to the increased risk of oral cancers in those individuals who consume wine, Mate, and smoke. This increase is also noted to be greater in those who smoke black tobacco over blond tobacco. Again, there is no direct implication that any one factor contributes more to this increase in oral cancers. Due to these other confounding factors, Mate may not be a carcinogen on its own but, due to the high temperature at time of consumption, may in fact be a means of increasing absorption for the carcinogens found in cigarette smoke and other environmental contaminants that are carcinogens or cancer promoters (Goldenberg and others 2004)."
Authors are with Dept. of Food Science and Human Nutrition, Univ. of Illinois, Urbana, Champaign, IL 61801, U.S.A.
My conclusion do not drink mate, coffee, or tea that is too hot. Do not smoke or drink too much alcohol.
If you would like a complete copy of this review I will be happy to send you one.