International Agency for Research on Cancer (IARC) - Summaries & Evaluations

Mate (Group 3)
Hot mate (Group 2A)

For definition of Groups, see Preamble Evaluation.

VOL.: 51 (1991) (p. 273)

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Mate, an aqueous infusion prepared from dried leaves of Ilex paraguariensis, is consumed mainly in Argentina, Bolivia, Brazil, Chile, Ecuador, Paraguay and Uruguay. It is usually drunk very hot following repeated addition of almost boiling water to the infusion. In Paraguay and southwestern Brazil, however, it is also drunk cold. Among numerous constituents, caffeine, theobromine and a number of chlorogenic acids have been identified in mate.

5.2 Experimental carcinogenicity data

No data were available to the Working Group.

5.3 Human carcinogenicity data

Three case-control studies in South America have investigated the association between mate drinking and oesophageal cancer. Two studies from Uruguay reported an increased risk among drinkers and dose-response relationships, even after adjustment for confounding variables, including alcohol consumption and smoking. Heavy drinkers of mate were approximately ten times more likely to develop cancer than people who did not drink mate. Another study in southern Brazil showed a nonsignificant increase in risk for oesophageal cancer among daily drinkers of mate after adjustment for confounding variables; however, intake levels were lower than in the previous studies, and no attempt was made to assess a possible dose-response relationship.

The role of mate in oral cancer was the subject of another case-control investigation in Brazil. The crude analysis showed a dose-response effect with the frequency of mate drinking, but this effect was no longer present after adjustment for smoking and alcohol consumption. After such adjustment, mate drinkers were 1.6 times more likely to have oral cancer than nondrinkers of mate - a nonsignificant difference. A case-control study from Uruguay reported a dose-response association between mate drinking and oropharyngeal cancer, which remained after adjustment for age, alcohol and smoking.

One study from Uruguay reported a three-fold increased risk for laryngeal cancer among mate drinkers, with a significant dose-response relationship after adjustment for age, tobacco and alcohol.

The results of a case-control study of bladder cancer in Argentina showed no evidence of trend in risk with increasing consumption of mate.

Overall, the case-control studies on mate drinking and cancer of the upper gastrointestinal tract suggest a strong association, whereas no such association was seen in one study of bladder cancer. These findings would be compatible with an effect of mate drinking due either to the composition of the beverage or to the temperature at which it is consumed or both, since all of these studies were conducted in populations that consume hot mate. No data were available on populations that drink cold mate. Some issues must be resolved before a conclusive result is obtained: (i) Awareness of the possibility that mate drinking may increase the risk of cancer of the upper gastrointestinal tract may have led to increased reporting of mate drinking for cancer cases as compared to controls. (ii) The results require confirmation by other groups of investigators. (iii) The possibility of residual confounding by alcohol drinking and tobacco smoking cannot be excluded entirely, although this was adjusted for in all of the studies.

5.4 Other relevant data

An endoscopic survey from southern Brazil showed that daily drinkers of hot mate had a prevalence of histologically confirmed oesophagitis which was three times higher than that of nondrinkers of mate.

5.5 Evaluation

There is limited evidence for the carcinogenicity of hot mate drinking in humans. No data were available on the drinking of cold mate.

There are no data on the carcinogenicity of mate in experimental animals.

Overall evaluation

Mate is not classifiable as to its carcinogenicity to humans (Group 3).

Hot mate drinking is probably carcinogenic to humans (Group 2A).

For definition of the italicized terms, see Preamble Evaluation.

Last updated: 17 November 1997

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