A University food science and nutrition professor has found yerba mate tea to have more antioxidants than green tea.

Yerba mate is less studied than green tea, but a growing body of scientific research on it has been published recently. In test tubes, the tea hinders growth of some kinds of cancer cells, but so far there is no proof of cancer-retarding properties in humans.

The South American tea is sold by companies that say it’s full of nutrients that fight disease, provide energy and aid weight loss. Research does show that yerba mate has positive effects on cells in test tubes, animals and some human studies.

Research by University professor Elvira de Mejia and her graduate students Caleb Heck and Laura Kim shows that the tea contains a greater concentration of antioxidants than green tea. Although yerba mate has more antioxidants than green tea, it has little or no catechines, a green tea ingredient linked to lowering the risk of prostate cancer.

“The difference is small, and depends on the brand and how you brew it,” de Mejia said.

Yerba mate has become increasingly popular despite its grassy taste because of health claims ranging from cancer-fighting ability to prevention of atherosclerosis, or hardening of the arteries. If you don’t like the bitter taste, you can add sweeteners, lemon or honey, but adding milk inhibits absorption of the tea’s antioxidants, de Mejia said.

“Yerba mate tea has the same energizing effect as coffee, but has a smoother balance stimulant effect and it lasts longer,” Heck said.

In South America, people drink it in gourds with straws, usually sharing it with a group of friends, Heck said. In the U.S., it is sold in tea bags, leaf tea and cold energy drinks.

Although yerba mate is high in antioxidants, it is not for everyone. Pregnant women and diabetics shouldn’t drink yerba mate because the tea contains caffeine. This could harm a fetus and raise blood sugar. Those who are at risk for esophageal cancer, like smokers and heavy drinkers, should sip sparingly because some studies found a higher occurrence of esophageal cancer in Uruguayans who drank more than four coups of yerba mate daily, compared with those who drank none, said de Mejia.

Kim, one of de Mejia’s graduate students, is studying yerba mate’s anti-obesity effects and whether or not it can be used as prevention or as treatment.

“So far I know that yerba mate has potential in anti-obesity,” Kim said.