Maté is widely advertised as a healthful beverage, said to provide all the presumed benefits of green tea, such as preventing cancer and heart disease. However, the basis for this claim is largely theoretical. Maté does contain antioxidant polyphenols similar to those in tea, but this by itself does not demonstrate that mate is health-promoting; numerous substances with strong antioxidant properties have failed to prove beneficial in double-blind, placebo-controlled studies. Even green tea itself has not yet been proven to offer any health benefits.

In the test tube, mate has shown effects that suggest possible value for reducing cancer risk.^1-3 However, these findings are far too preliminary to rely upon; in fact, there is stronger evidence that maté could under certain circumstances increase risk of cancer (see Safety Issues).

Other proposed benefits of maté also largely lack foundation. One study found that an extract of mate could help slow glycation, a metabolic side effect of diabetes.⁴ These findings have been used to claim that maté is healthful for people with diabetes. However, this study did not involve people with diabetes; it involved chemicals in a test tube. Tens of thousands of substances show benefits in the test tube that fail to translate into real life; it is greatly premature to claim that maté is helpful for people with diabetes based on these exceedingly preliminary findings.

Similarly weak evidence hints that maté might increase fat metabolism,⁵ and on this basis maté has been proposed as a weight-loss agent. However, there are no published human studies of maté that show any weight loss benefit. One small double-blind, placebo-controlled study evaluated an herbal preparation containing maté combined with guarana(Link tonew article) and damiana.⁶ The herbal mixture appeared to cause participants to feel full more quickly during a meal, and to continue to feel full for longer after the meal; this led to modest, short-term weight loss. However, it is not clear to what extent the maté in this product played a role.

Another study found that maté might increase bile flow and speed the action of the intestines ⁷; these reported effects, even if real, do not indicate any particular health benefit.

Although some maté proponents attempted for many years to maintain that maté does not contain caffeine (supposedly it contained a chemical called “mateine,” which, in fact, does not exist), maté does in fact contain caffeine. Depending on how it is brewed, maté tea contains somewhat more caffeine than black tea and slightly less caffeine than coffee. Based on this caffeine content, maté would be expected to enhance mental function and improve sports performance.

As a widely consumed beverage maté is generally assumed to be entirely safe. However, this may be an incorrect assumption. Numerous studies have found associations between high consumption of maté in South American and increased rates cancer of the esophagous, mouth, throat, and larynx.^8-10 It is widely stated that this increased risk is entirely due to the practice of drinking maté at very high temperatures. However, the underlying evidence is not so clear-cut. The data actually suggest that at least some of this increased risk is be due to the maté itself, rather than the temperature at which it is consumed.¹⁰ In addition, maté consumption has also been associated with increased risk of kidney and lung cancer, which would not be expected to be influenced by beverage temperature.^11,12 Finally, there is some direct evidence that mate has carcinogenic effects.¹³ Putting all this information together, it does appear that maté is at the very least slightly carcinogenic. However, so is charred hamburger; moderate use of maté is not likely to significantly increase cancer risk.

Other potential problems with maté relate to its caffeine content. Potential side effects of caffeine include heartburn, gastritis, insomnia, anxiety, and heart arrhythmias (benign palpitations or more serious disturbances of heart rhythm.)¹⁴ All drug interactions that can occur with caffeine would be expected to occur with maté as well (see next section).

Maximum safe doses have not been established in pregnant or nursing women, young children, or people with severe liver or kidney disease.

• MAO inhibitors: The caffeine in maté could cause dangerous drug interactions.
• Stimulant drugs such as Ritalin: The stimulant effects of maté might be amplified.
• Drugs to prevent heart arrhythmias or treat insomnia, heartburn, ulcers, or anxiety: The caffeine in maté might interfere with their action.