Cancer and yerba mate consumption: a review of possible associations.

OBJECTIVE

To identify any possible link between mate consumption and cancer, mainly of the esophagus, larynx, and oral cavity.

METHODS

A review of literature, published through August 2008, pertaining to the carcinogenic risk of mate consumption was undertaken by searching the two databases, MEDLINE and TOXLINE, for relevant articles. The bibliographies of the articles were examined for additional relevant sources. In addition, a search on the name of each author having published on the topic was conducted. The epidemiological studies are presented by cancer site; experimental works are examined in dedicated sections; and the discussion combines epidemiological and experimental evidence.

RESULTS

Almost all epidemiological studies shared similar methodology: hospital-based, case-control studies where participants were personally interviewed on the main risk factors, using similar questionnaires. Several studies found an association between the temperature of the mate infusion and oral, esophageal, and/or laryngeal cancer risks; while a few focused on carcinogenic contaminants introduced during the industrial processing of the leaves. The cancer most frequently mentioned in association with hot mate with bombilla (drunk through a metal straw) was the esophagus. Size, exposure assessment, methods of analysis, and quality were different among the studies reviewed. The results varied greatly. The higher risk estimate (odds ratio = 34.6) was found for women who drank 1 L or more daily; for men it was only 4.8. Risk increased with duration, daily quantity, and temperature at drinking. The synergic action between mate, alcohol, and tobacco was a clear result in several studies, and in some, nutritional deficiencies and poor oral hygiene played a role. No increased risk was associated with cold mate beverages.

CONCLUSIONS

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. The temperature could act by damaging the mucosa or accelerating metabolic reactions, including those with carcinogenic substances in tobacco and alcohol. However, there is no sound population-based case-control study on mate consumption as a risk factor for cancer. This, coupled with the range of results on mate risk, make assessing the etiological fraction difficult. More research needs to be done before a definitive statement can be made regarding cancer risk associated with any of the various forms of mate consumption. Future research should include population-based studies; collection of data on consumption of tobacco, alcohol, hot drinks, fresh fruit, and vegetables; and, a method to precisely measure volume and temperature of mate intake.