Maté contains xanthines, which are alkaloids in the same family as caffeine, theophylline, and theobromine, well-known stimulants also found in coffee and chocolate. Maté also contains elements such as potassium, magnesium and manganese Caffeine content varies between 0.3% and 1.7% of dry weight (compare this to 2.5–4.5% for tea leaves, and 1.5% for ground coffee).
Maté products are sometimes falsely marketed as “caffeine-free” alternatives to coffee and tea, and said to have fewer negative effects. This is based on a mistaken claim that the primary active xanthine in maté is “mateine”, erroneously said to be a stereoisomer of caffeine. However, it is not chemically possible for caffeine to have a stereoisomer, and “mateine” is an official synonym of caffeine in the chemical databases.
From reports of personal experience with maté, its physiological effects are similar to (yet distinct from) more widespread caffeinated beverages like coffee, tea, or guarana drinks. Some users report a mental state of wakefulness, focus and alertness reminiscent of most stimulants, but often remark on maté’s unique lack of the negative effects typically created by other such compounds, such as anxiety, “jitteriness”, and heart palpitations.
Studies of maté, though very limited, have shown preliminary evidence that the maté xanthine cocktail is different from other plants containing caffeine most significantly in its effects on muscle tissue, as opposed to those on the central nervous system, which are similar to those of other natural stimulants. The three xanthines present in maté have been shown to have a relaxing effect on smooth muscle tissue, and a stimulating effect on myocardial (heart) tissue.
Maté’s negative effects are anecdotally claimed to be of a lesser degree than those of coffee, though no explanation for this is offered or even credibly postulated, except for its potential as a placebo effect. Some users report that drinking yerba maté does not prevent them from being able to fall asleep, as is often the case with some more common stimulating beverages, while still enhancing their energy and ability to remain awake at will. However, the net amount of caffeine in one preparation of yerba maté is typically quite high, in large part because the repeated filling of the maté with hot water is able to extract the xanthines very effectively. It is for this reason that one maté may be shared among several people and yet produce the desired stimulating effect in all of them
In vivo and in vitro studies are showing yerba maté to exhibit significant cancer-fighting activity. Researchers at the University of Illinois (2005) found yerba maté to be “rich in phenolic constituents” and to “inhibit oral cancer cell proliferation” while it promoted proliferation of oral cancer cell lines at certain concentrations.
On the other hand, a study by the International Agency for Research on Cancer showed a limited correlation between oral cancer and the drinking of hot maté (no data were collected on drinkers of cold maté). Given the influence of the temperature of water, as well as the lack of complete adjustment for age, alcohol consumption and smoking, the study concludes that maté is “not classifiable as to its carcinogenicity to humans”. Yerba maté consumption has been associated with increased incidence of bladder, esophageal, oral, squamous cell of the head and neck, and lung cancer.
The pyrrolizidine alkaloids contained in maté tea are known to produce a rare condition of the liver, veno-occlusive disease, which produces liver failure due to progressive occlusion of the small venous channels in the liver. One fatal case has been reported in a young British woman who consumed large quantities of maté tea from Paraguay for years.
An August 11, 2005, United States patent application (documents #20050176777, #20030185908, and #20020054926) cites yerba maté extract as a monoamine oxidase inhibitor; the maximal inhibition observed in vitro was 40–50%. MAOIs being antidepressants, there is speculation that this may contribute to the calming effect of yerba maté.
In addition, it has been noted by the U.S. Army Center for Health Promotion and Preventive Medicine that yerba maté can cause high blood pressure when used in conjunction with other MAO inhibitors (such as Nardil and Parnate).
Emerging research also shows that yerba maté preparations can alter the concentration of members of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) family, resulting in an elevated level of extracellular ATP, ADP, and AMP. This was found with chronic ingestion (15 days) of an aqueous yerba extract, and might lead to a novel mechanism for manipulation of vascular regenerative factors, i.e., treating heart disease
Source: Wikipedia, under Yerba Mate