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Found an interesting article that seems to base its statements on lots of research. I haven't checked out the studies themselves but this review article seems to state that yerba mate does in fact contain considerable amounts of carcinogenic compounds (in addition to the previously proven antioxidants) and should probably not be consumed in large quantities because of this.

Kind if disappointing because I've really begun to like mate and the energy it gives me. I'm going to have to look around more and decide whether I want to continue purchasing it or not.

The article can be found here: http://www.caring4cancer.com/go/cancer/ ... /questions

sigh*...what doesn't give you cancer.

Hm I am not sure but they should probley keep testing this and keeping track. I think its up to the drinker to decide how much risk they think it would be to them.

As quoted in the article, the cancer seems to be linked more to the daily consumption of scalding hot mate. Having grown up in Brazil, I observed that the mate drinkers of the south tend to drink only hot mate, instead of water and other drinks, so imagine that amount of hot water going through your throat! Any drink will give you cancer like that!
I have done some personal research on mate and found that even in the areas where it is consumed extensively, cancer cases are not above average. In fact, they usually register lower that most areas, but those types of studies have so many variables it's hard to define exactly what all is influencing the result.
Just remember, though, that usually research like this is done usually by applying concentrated amounts of extract to a cell and observing the mutations. Just about anything carried out in this way will "cause cancer". They really need to do a controlled study on humans over the span of several years - something no one will be willing to attempt.

Yes, it mentions the heat of the brew being a factor, but then it goes on to discuss in depth polycyclic aromatic hydrocarbons (PAHs) which are classified as carcinogens.

PAHs, like most potentially "unhealthy" compounds, are found in small amounts in many foods, so they (sort of) compared PAH levels in green tea to that in mate. It later says that they actually only measured PAH levels in green tea leaves, not the actual brew. When comparing mate leaves to tea leaves, mate had 2 to 11 times as many PAHs. This still isn't very clear; two times as many PAHs might mean nothing, while 11 might be significant. They state that brewed mate still had significant PAH levels but they do not compare it to brewed green tea.

What is most striking is that they go on to say that the amount of PAH consumed by a "traditional" mate drinker equates to the PAH consumed by smoking a pack of cigarettes a day. I for one have no interest in taking in an amount of chemicals equal to a pack of cigarettes a day; there's a reason I don't smoke. Surely there are dozens of other chemicals (and just the tar and smoke itself) in cigarettes that make them far more unhealthy, but that comparison irked me.

Burning your mouth with scalding liquid and then chain smoking...not a good combo.

I lived in Paraguay for 2 years, and not only do they drink yerba mate all the time, but it is incredibly strong compared to how we drink it in the U.S. If there is a problem with mate, surely it must manifest very clearly in South American drinkers, which I don't believe is the case. In the meantime,if you're drinking a few tablespoons rather than a few cups of the dried herb each day, I don't think there is anything to worry about.

teaisme wrote:If there is a problem with mate, surely it must manifest very clearly in South American drinkers, which I don't believe is the case.

well... there is a high % of penile cancer in Paraguay ... coincidence

From the wikipedia page:

"When the yerba is harvested, the branches are dried sometimes with a wood fire, imparting a smoky flavor."

"...researchers in Mississippi found that both cold and hot water extractions of yerba mate contained high levels (8.03 to 53.3 ng/g dry leaves) of carcinogenic polycyclic aromatic hydrocarbons (PAHs)"

Duh. PAHs do not spontaneously arise in heat-treated leaves. Woodfire smoke is also responsible for PAH uptake in grilled foods, although the primary carcinogenic compounds formed in cooked meat arise from a process called carmelization of proteins. Eating vegetables appears to mitigate the carcinogenic effects of grilling, as does marinating (different reasons).

The oncogenic effect reported in (epi- and endothelial) cells of the skin, upper GI tract/head and neck, bladder and lungs appear to be consistent with toxic metals such as arsenic that overwhelm natural reductive capacity or supplant selenium at the active site of glutathione enzymes. These metals are bioaccumulated in many plants.

Arsenic contamination of tea has been reported/studied. It's usually found in cheaper teas, grown at low elevation in contaminated watersheds that are downstream from mining areas or as a result of "natural" groundwater contamination in river valleys catalyzed by surface water nitrates acting on natural sediments or underlying rock (nitrate sources include agriculture, urban pollution).

Yerba mate chemistry has not been studied in depth.

An aside: http://www.noborders.net/mate/what.html

"Mate has a characteristic mature flavor which is somewhat sweet, bitter, withered leaf like, and alfalfa-like, similar to that obtained from tea (Camellia sinensis)[1]. Of the 196 volatile chemical compounds found in Yerba Mate, 144 are also found in tea. "

1. Kawakami, M. and Kobayashi, A.; Volatile Constituents of Green Mate and Roasted Mate, J.Agric.Food Chem. 39, 1275 (1991).

The wikipedia page cites six scientific studies showing higher cancer rates associated with Yerba Mate use. There's also a (less common, but significant enough to be mentioned) problem of liver damage.

It seems enough to concern me; I'll drink it occasionally but would not recommend regular use.

One additional thing to consider...in cultures where people have been exposed to something for generations, people may have adapted to possible negative effects. For example, this is why Native Americans have very low rates of allergies to poison ivy.

Yerba Mate has been consumed for at least a few hundred years by people of European ancestry living in south America, and much longer than that by certain native peoples of South America, but it has only recently started to be consumed in other regions. It was introduced to Europe earlier but never caught on the way tea or coffee did. That's enough to make me at least cautious.

AlexZorach wrote: The wikipedia page cites six scientific studies showing higher cancer rates associated with Yerba Mate use. There's also a (less common, but significant enough to be mentioned) problem of liver damage.

It seems enough to concern me; I'll drink it occasionally but would not recommend regular use.

One additional thing to consider...in cultures where people have been exposed to something for generations, people may have adapted to possible negative effects. For example, this is why Native Americans have very low rates of allergies to poison ivy.

Yerba Mate has been consumed for at least a few hundred years by people of European ancestry living in south America, and much longer than that by certain native peoples of South America, but it has only recently started to be consumed in other regions. It was introduced to Europe earlier but never caught on the way tea or coffee did. That's enough to make me at least cautious.

Yerba mate is safe to drink frequently and even daily. If there were really a risk of liver damage or cancer you would have large populations-literally millions of people, dying of cancer in Argentina, southern Brasil, Paraguay, and Uruguay.