Posted by: Christopher Maloney, Naturopathic Doctor | September 15, 2012

Does Yerba Mate Cause Esophageal Cancer?

English: Yerba mate

English: Yerba mate (Photo credit: Wikipedia)

The short answer is no.  The longer answer is much more complicated.

I was looking into the weight loss effects of Yerba Mate (more of that on my website:  maloneymedical.com) and found a fairly stunning review of Yerba Mate claiming it almost tripled a person’s risk of esophageal cancer.  How could this be?

Looking a bit deeper, the review was based on population studies in South America and did not account for the differences in tea drinking.  Those who drank Yerba Mate tea at very hot temperatures and who drank more than a liter a day were at double the risk of those who drank smaller amounts of warm tea.  In comparison, those who combined alcohol, cigarettes, and the tea were seven times more likely to get esophageal cancer.  Another study looked at the effect of other hot drinks:  “Consumption of other very hot beverages, such as tea and coffee with milk but not coffee alone, was also significantly associated with an increased risk, in the 2- to
4-fold range.” (Int J Cancer. 2000 Nov 15;88(4):658-64.)  Evidently the preparation of proper Mate tea involves brewing it at almost boiling temperatures.

At the same time:  “Yerba Mate has been shown to be hypocholesterolemic, hepatoprotective, centralnervous system stimulant, diuretic, and to benefit the cardiovascular system.  It has also been suggested for obesity management. Yerba Mate protects DNA from  oxidation and in vitro low-density lipoprotein lipoperoxidation and has a high antioxidant capacity.” (J Food Sci. 2007 Nov;72(9):R138-51.)

In looking for whether Yerba Mate might increase the risk of cancers by any chemical means, I came across the fact that Yerba Mate can cause cellular changes.  But “since caffeine is one of the most abundant compounds found in the dry mass of mate, we conducted additional experiments with caffeine alone. We showed that caffeine used at the same concentrations manifests a more potent cyto- and genotoxic effect that may account, at least in part, for the disadvantageous effects observed for yerba mate extract.”  (Mutat Res. 2009 Sep-Oct;679(1-2):18-23.)  In other words, caffeine would increase your risk of cell changes more than Yerba Mate.

Here’s the rub.  Yerba Mate doesn’t increase esophageal or upper body cancers more than any other liquid that is drunk at a burning temperature in high quantities.  There are no studies that show Yerba Mate is a problem once it has cooled.  What evidence we do have is that compounds in the Mate may buffer the effect of both temperature and caffeine.

Now for a little good news. “Our data show improvements in both the basal glucose blood levels and in the response to insulin administration in the treated animals. The molecular analysis of insulin signalling revealed a restoration of hepatic and muscle
insulin…”  Now that’s a reason to drink a tea.

In full disclosure, I do drink a cup of Yerba Mate tea most mornings.  Click on the link below to learn why.  All the abstracts I used for this post are at:  http://www.maloneymedical.com/id164.html

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