The other day, I received an email from the VP of Operations of Guayaki Yerba Maté in response to my earlier post about the drink and its links to cancer. Since my post sparked a lot of discussion, I thought I’d share his note. He said:
I’m writing from Guayakí Yerba Mate in response to your article on PLoS today. We would value the opportunity to discuss this topic in more detail and provide additional research and information below. I am available this week or next for a phone call.
The first point to note is that the link between yerba mate and cancer is based on epidemiological studies which are known to be unreliable. This is due in large part to environmental factors, cultural practices and varying medical support systems. Some of the key factors not taken into consideration are water quality, quality of the yerba mate, consumption patterns, processing methods and temperature of water used.
Some studies have linked cancer with the consumption of very hot water and similar links have been found in tea and coffee consumed in very hot water, as you have noted, thank you. Many experts do believe that the potential risk is due to PAH, polycyclic aromatic hydrocarbons. Human and environmental PAH’s are found virtually everywhere including foods and beverages such as barbecued meats, shellfish, water, coffee and tea. Research suggests that PAH may result from environmental pollution, harvesting and smoke finishing processes. It’s important to note that organic, air-dried yerba mate is found to contain lower amounts of PAH than green tea in recent testing.
I also attached a recent study published in Comprehensive Reviews in Food Science and Safety. Note page 313 (excerpt also pasted below).
I welcome a conversation on this topic and hope to hear from you.
Thanks for your time,
Guayaki SRP, Inc.
And the excerpt, from Comprehensive Reviews in Food Science and Safety, Volume 9, 2010 Page 313
“…concerns have been raised regarding an association between yerba mate and the occurrence of certain types of cancer, specifically oral, esophageal, lung, bladder, and renal (Heck and de Mejia 2007). However, there is no conclusive evidence that this association is a result of the consumption of yerba mate but rather due to various lifestyle choices including smoking and excessive alcohol consumption. In addition, these cases have primarily been reported in certain areas of South America where large amounts of yerba mate are consumed at very hot and damaging temperatures which could lead to increased absorption of carcinogens found in cigarette smoke or other environmental pollutants (Heck and de Mejia 2007).”
It’s nice to see that Mr. Bruehl did actually read my post. And some of the points he makes are similar to ones I made. For instance, yes: case-control studies do not prove causality, and the studies that have been published about Yerba maté did not control for every factor that might influence outcome, as I mentioned. That said, some of these studies did collect information on consumption patterns (in terms of quantity consumed) and temperature. And many tried to control for tobacco and alcohol consumption, too.
In my opinion, Bruehl’s tactic here is pure manufactured doubt—”we can’t prove beyond a shadow of a doubt that it’s the Yerba maté causing the cancer”—which is pretty much exactly what the tobacco, asbestos, and lead industry did when science started to suggest their respective dangers. (For more on industry doubt campaigns, I highly recommend Doubt is Their Product by David Michaels, former Assistant Secretary of Energy.) I know, it’s unfair of me to compare the Yerba maté industry to Big Tobacco, but I’m just trying to make the point that these kinds of arguments surface again and again in industry, and I’m not at all convinced by them.
Mr. Bruehl is, of course, right that PAH’s are found in other foods. But personally I think this is a cause for more concern, not less. The fact that the world is full of dangerous exposures does not make me feel better, nor does it make this particular exposure any less worrying! Plus, considering that Yerba maté is marketed as an “anti-cancer drink,” the fact that there is more evidence suggesting it increases rather than decreases cancer risk is particularly disturbing. (To be fair, Guayaki does not tout Yerba maté as an anti-cancer drink, but their website does have a page dedicated to its antioxidant capacity, and it calls maté “the healthiest” stimulant drink around.)
I will concede Mr. Bruehl’s last point: it may well be true that organically grown Yerba maté is purer and potentially safer. I can’t find evidence to back this up, but logically it would make sense if it’s grown with fewer chemicals. So if I were going to reach for some Yerba maté—and chances I are never will—I’ll be sure it’s the certified organic kind.