Yerba Mate Side Effects
Caffeine, Cancer and Pregnancy Risks

Yerba mate has been consumed by people in South America for centuries, and it is classified by the Food and Drug Administration as “Generally Recognized as Safe.”

However, that does not mean that it is completely without side effects. Before you start drinking mate, it is important to be aware of the side effects and dangers.

Like coffee and tea, yerba mate contains caffeine.

Some companies that sell yerba mate claim that the boost you get from drinking it is caused by a chemical they call “mateine,” and that yerba mate has little, if any, caffeine.

These companies say that “mateine” has all of the positive effects of caffeine without side effects like nervousness and anxiety. However, mateine is just another word for caffeine.

This is what Dr. Leslie Taylor, an herbalist and author of "The Healing Power of Rainforest Herbs" states:

So, how much caffeine does yerba mate contain?

A 2005 study published by the researchers at the University of Sao Paolo analyzed several popular brands of mate and found that the amount of caffeine varied depending on the type of mate and the brewing method.

One cup (182 milliliters) of mate tea made from roasted leaves contained only 13 milligrams of caffeine.

One "cuia" (500 milliliters) of Tererê contained an average of 85 milligrams of caffeine. This is a cold-brewed beverage made from dried green mate leaves

One "cuia" (500 milliliters) of Chimarrão contained an average of 135 milligrams of caffeine. This is the hot mate made from dried green mate leaves.

What does this mean?

An 8 ounce cup of coffee usually has anywhere from 60 to 120 milligrams of caffeine. When you consider that an 8 ounce cup is only about half a cuia, you can see that even the most caffeinated mate drinks have less caffeine in them then coffee.

So, if you are trying to cut back on caffeine without eliminating it entirely, switching to yerba mate instead could help. However, it is still entirely possible to consume enough yerba mate to cause caffeine-related side effects like anxiety, insomnia and rapid heartbeat.

Also, unlike green tea, yerba mate does not contain theanine, the amino acid that blunts the side effects of coffee. Just as with coffee, the key to avoiding side effects from the caffeine in yerba mate is knowing when to stop.

Pregnant women have to be especially careful about what they eat and drink. Anything containing caffeine is suspect, since some studies have indicated that drinking caffeinated beverages like coffee can cause low birth weight, miscarriages and other problems.

Most doctors agree that low-to-moderate caffeine consumption is safe during pregnancy, while others advise their patients to avoid it entirely.

Research indicates that consumption of yerba mate during pregnancy does not increase the risk of prematurity and low birth weight; however, moderation and caution is still advised.

While researchers at the Federal University of Pelotas found that mate drinking was not associated with prematurity or low birth weight, a 2007 case study of a mother who consumed excessive amounts of mate while pregnant found that her baby exhibited signs of withdrawal after birth, including “increased jitteriness and irritability, high-pitched cry, hypertonia in the limbs, and brisk tendon reflexes.”

If you are pregnant or nursing, you should definitely follow your doctor's advice when it comes to drinking mate.

One of the most disturbing possible side effects of yerba mate consumption may be an increased risk of cancer. When I discovered this, I felt blindsided. How could a drink that was supposed to be so healthy and good for you increase your risk of cancer?

But several studies performed over the past decade have linked yerba mate consumption to an increased risk of oral cancer, cancer of the esophagus, lung and renal cancer. These studies are far from conclusive.

As a matter of fact, a 2009 review of the medical literature said that while “The role of hot mate in increasing the risk of cancer of esophagus, larynx, and oral cavity seems to be supported by several epidemiological studies...there is no sound population-based case-control study on mate consumption as a risk factor for cancer.”

More research is needed to determine what the risk, if any, mate poses when it comes to cancer.

Some scientists have suggested that the risk of oral cancers may increase in hot mate drinkers simply because they tend to consume mate through a straw at a very high temperature. The high temperature of the drink may damage the esophagus, leading to an increased cancer risk over time. Supporting this theory, some studies only show an increased cancer risk when mate is consumed hot, not when it is consumed cold.

However, other research suggests that the apparent increase in cancer risk may come from carcinogenic compounds called polycyclic aromatic hydrocarbons.

Another yerba mate side effects study published in 2008 found “very high concentrations of carcinogenic PAHs were found in yerba mate leaves and in hot and cold mate infusions.”

Additionally, a study published in 2006 examined the urine of 200 Brazilian subjects for 1-OHPG, a metabolite of PAHs, and found that “any maté consumption significantly increased urine 1-OHPG concentrations and that there was a step-wise increase in 1-OHPG concentration with the volume of maté consumed. “

To avoid yerba mate side effects, drink in moderation, and avoiding drinking it at extremely high temperatures.

Hearn, Kelly, “Tempest in a Teapot.” http://www.alternet.org/environment/20510

Deborah H. Markowicz Bastos, Ana Claudia Fornari, Yara S. de Queiroz, Rosana Aparecida Manolio Soares & Elizabeth A.F.S. Torres (2005). “The Chlorogenic Acid and Caffeine Content of Yerba Maté (Ilex paraguariensis) Beverages” Acta Farm. Bonaerense 24 (1): 91-5 (2005).

Loria D, Barrios E, and Zanetti R (2009). Cancer and yerba mate consumption: a review of possible associations. Rev Panam Salud Publica. 2009;25(6):530–9.

Martín, Itziar MD, PhD; López-Vílchez, María Ángeles MD, PhD; Mur, Antonio MD, PhD; García-Algar, Óscar MD, PhD; Rossi, Silvia BSc; Marchei, Emilia BSc; Pichini, Simona PhD (2007). Neonatal Withdrawal Syndrome After Chronic Maternal Drinking of Mate. Therapeutic Drug Monitoring: February 2007, pp 127-129

Iná S. Santos2, Alicia Matijasevich and Neiva C. J. Valle (2005). Maté Drinking during Pregnancy and Risk of Preterm and Small for Gestational Age Birth. 2005 The American Society for Nutritional Sciences J. Nutr. 135:1120-1123, May 2005

Renato B Fagundes, Christian C Abnet, Paul T Strickland,, Farin Kamangar, Mark J Roth email, Philip R Taylor, and Sanford M Dawsey (2006). “Higher urine 1-hydroxy pyrene glucuronide (1-OHPG) is associated with tobacco smoke exposure and drinking maté in healthy subjects from Rio Grande do Sul, Brazil” BMC Cancer 2006, 6:139doi:10.1186/1471-2407-6-139

Farin Kamangar1, Michele M. Schantz, Christian C. Abnet, Renato B. Fagundes and Sanford M. Dawsey (2008). High Levels of Carcinogenic Polycyclic Aromatic Hydrocarbons in Mate Drinks. Cancer Epidemiology, Biomarkers & Prevention. May 2008 17; 1262

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