Anyway, a few years ago a drink called "yerba mate" burst into the mainstream and was touted as a miracle drink, with people claiming it provided a super-duper energy burst (with no ill effects) and that it was better for you than even green tea. I haven't seen it around so much lately, but many are still a little confused about how it stacks up to tea. I'll attempt to illuminate the world (or at least my readers--if any of you are left) below.
Yerba mate is a plant that grows in South America and is drunk in most of the countries there. I personally don't like it, as it tastes very vegetable-like and sort of grassy like green tea, but some people like that kind of thing. It's actually pretty nutritious and contains a lot of vitamins and minerals, as well as antioxidants and such (though just about EVERY plant contains antioxidants--antioxidants serve to protect the plant from the sun's rays). And because the people in South America are clearly still alive, mate can't be poisonous or toxic or anything.
Even more compelling is the fact that while yerba mate does contain a form of caffeine, it acts differently in the human body. It stimulates without making you jittery, as it affects muscle tissue moreso than the nervous system (which is what coffee and tea affects).
However, as far as containing more antioxidants than green tea (or more effective ones), mate falls short. It's good for you, but it's not green tea. I don't know how it stacks up to rooibos or black tea (there doesn't seem to be any literature), but green tea still reigns in that department. Also, yerba mate has been connected with several forms of cancer, including oral, esophageal, stomach, bladder, and lung cancers. There isn't any conclusive evidence to show that it actually causes these cancers, but I'd recommend enjoying it in moderation or abstaining completely from it until there's more data.
Other resources:
http://pixiemate.com/mate-studies.html
http://www.mayoclinic.com/health/yerba-mate/AN01774
