Yerba Mate, like coffee and tea, is considered safe by the United States Food and Drug Administration, and is on their GRAS (Generally Recognized as Safe) list.
Yerba Mate is known to be a healthy alternative to coffee, one of the most nutritious drinks in the world, and when used properly it has a long and ancient history of safe, personal enjoyment. That being said, even hot soup comes with a warning. And Yerba Mate is a lot more nutrient packed than almost any soup.
Knowledge is power. We have the first and largest Internet Library of yerba mate information. Below is everything we have collected about any potential risks, and it is important to note that yerba mate is not without its risks. Care should be taken in its preparation and use, as it will affect your body. Please consider the following suggestions:
Yerba mate can effect blood pressure. For this reason, it is not recommended before surgery. (Liberti L, Beutler JA, Cirigliano M, et al, eds. The Review of Natural Products. St Louis, Mo: Facts and Comparisons, 2003)
"For otherwise healthy nonpregnant, nonnursing adults who are not taking other substances or medications containing caffeine, [Yerba] Mate is considered relatively safe in amounts typically recommended." (Michael Castleman, medical reviewer, Sheldon Saul Hendler, THE HEALING HERBS.).
Latin American women have always claimed Yerba Mate to be an important part of a healthy pregnancy. Researchers tested it to see if it influenced negatively the growth of the child. A study published in The Journal of Nutrition concurs: "In conclusion, prevalence of daily mate drinking was high among pregnant women and contrary to the hypothesis, no harmful effect on intrauterine growth or duration of pregnancy was detected." (Santos, 2005)
Consumption of drinks (coffee, tea, hot water) or soups at very high temperatures has been reported as a risk factor for esophageal cancer in Puerto Rico (30), Singapore (31), Iran (32), and China (33), (34), (35).
For those on medications, they should note the following drug interactions (Brinker F. Herb Contraindications and Drug Interactions, 2nd ed. Sandy (OR): Eclectic Medical Publications, 1998):
Aspirin: Yerba mate may increase absorption and bioavailability.
Acetaminophen: Pain relief of acetaminophen is increased due to caffeine content in mate.
Benzodiazepines: Effects of benzodiazepines are reduced by caffeine content in yerba mate.
Beta-Adrenergic Agonists: Effects of beta-adrenergic agonists are increased by yerba mate.
Clozapine: Yerba mate may alter effects.
CNS Stimulants: Yerba mate may increase effects.
Monoamine-oxidase inhibitors (MAO-I): Yerba mate can cause hypertensive crisis.
Theophylline: Yerba mate may increase effects and lead to possible toxicity.
Diuretics: Yerba mate may cause an additive effect.
Cholesterol-lowering drugs: Yerba mate is a great source of antioxidants, yet some heart experts say that taking antioxidants in combination with cholesterol-lowering drugs can actually be hazardous.(WebMD)
To be safe, consider avoiding Yerba Mate if you have been asked to avoid caffeine. Although the caffeine appears to be bound uniquely, it is still caffeine. Therefore, patients with hypertension, cardiac disorders, and anxiety should not consume mate.
Since drinking very little water with tea is an ancient and important principle, it can not be safely reccomended to drink copious amounts of water with Yerba Mate in order to intake more chemicals. Rather, it is best to use as little water as possible each time when consumed. Subhuti Dharmananda, Ph.D., Director, Institute for Traditional Medicine in Portland, Oregon examined classical medical literature for recommendations on the amount of water to drink with hot tea. His review highlights the Chinese and Ayurvedic tea principle of "just a few sips" (use as little water as possible)" (2005). We caution against drinking too much water with yerba mate as there is no historical precedence for doing so. It is neither traditional nor common practice. Fortunately, the Traditional Method of yerba mate preparation is designed to use less water than one would use if soaking a tea bag.
Drinking any liquid (coffee, tea), even Yerba Mate, at very high temperatures and in large quantities over time may increase the risk of esophogal cancer. Unfortunately, a large number of Yerba Mate cultures drink it at too high of a temperature and over 5 times a day, taking more than just a few sips each time. In some Latin American cultures it is considered cool, or machismo, to drink the water at a very hot temperature. The American Association for Cancer Research notes that consumption in larger quantities and at very hot temperatures is "associated with an elevated risk of esophageal cancer"(2003).
The practice of Traditional Medicine suggests drinking tea 3-5 times a day, yet Dharmananda notes that it does not reccommend drinking excess amounts of water with tea, nor drinking it at excessively hot temperatures (2005). The American Association for Cancer Research highlighted the risks of excess:
For those drinking more than 1 liter/day at very hot temperatures: Subjects who self-reported drinking mate at a very hot temperature had an almost 2-fold increase in risk [odds ratio (OR), 1.87, 95% CI, 1.17-3.00] compared with those drinking warm to hot mate, after adjusting for cumulative consumption of mate. Mate amount and temperature were observed to have independent effects and, although no departure from multiplicativity was observed between the two covariates, those drinking more than 1 liter/day of mate at a very hot temperature had a 3-fold increase in risk (OR, 2.95, 95% CI, 1.30-6.74) compared with those drinking less than 0.5 liter/day of mate at a warm to hot temperature. Subjects with high cumulative exposure to mate in the presence of low alcohol and tobacco exposures presented a lower-risk estimate (OR, 1.52, 95% CI, 0.88-2.62), whereas those with high cumulative exposures to mate, alcohol, and tobacco presented a 7-fold increase in esophageal cancer risk (OR, 7.10, 95% CI, 3.75-13.46). The population-attributable fraction as a result of mate consumption was calculated to be 53%, of which the sole effect of amount and temperature was 14.8 and 12.6% respectively, and 14.9% was attributable to high mate consumption at high temperature. (2003) The evidence highlights the risk of using very hot water and taking more than "just a few sips." Recall, the tea has many anti-oxidents that help to fight cancer, but is most effective when following the Traditional Method. As the saying goes, "best to avoid too much of a good thing." Use the Yerba Mate wisely.
Police or other enforcement agencies could incorrectly assume that the gourd is being used for illegal drugs. Some students have reported being suspended from the university while their yerba mate gourds were investigated. This is not a completely uncommon occurrence. Raul, from Argentina, tells a not too uncommon story. He talks about the police detaining him while they call in to the station to ask about "Yerba Mate, One Litro, Industria Argentina." Be aware that the Traditional Method is an uncommon site and may require some explaining. For this reason, many choose to use a YerbaCup in public.