Unfortunately, little is known about Yerba mate. The scientific evidence on more well-understood drinks like tea is still full of a lot of uncertainty, and with Yerba mate, where the studies are scarce and to some degree conflicting, it’s a big area of uncertainty.
There are epidemiological studies showing increased risk of cancer associated with Yerba mate, but this may be confounded by heavy smoking and drinking in the populations, and it also could be that people drink it through a straw, which can lead to burns, increasing the risk of cancers of the mouth and throat. It’s very antioxidant rich, and in vitro experiments show potential anti-cancer activity.
I’ve been collecting this information on a page about Yerba mate which cites and summarizes these studies and articles. If anyone has any other studies that I haven’t cited, or any deeper readings of those studies that they think would enrich the article, please let me know!
I can tell you that I drink Yerba mate and I enjoy it. But it is a bit strange; the way it makes me feel is very different from how tea or coffee makes me feel. It does not aid my concentration the way tea and coffee do, and I find it somewhat relaxing. I only consume it in the late afternoon…any other time of day I’m not crazy about how it makes me feel. And because little is known about it, I am cautious about drinking a lot of it on a regular basis. I have started to really like the way it tastes though. It took me some time to develop a taste for it but now I find it quite delicious, and there’s a fair amount of diversity, based on whether it’s green, roasted, aged, or smoked. (And it can be all / none / any combination of roasted, aged, or smoked)