Maté is an evergreen tree native to Argentina, Brazil, Paraguay, and Uruguay. The leaves and small stems of the tree are used to make a tea-like caffeinated beverage. Maté has traditionally been used to enhance alertness and mental function, and also to treat digestive problems.

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. Evengreen 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 withguarana(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.