According to the Brazilian Ministry of Health, southern Brazil has incidence rates for ESCC of approximately 20.4/100,000/year for men and 6.5/100,000 for women. These rates are much higher than those observed in most western countries. Several epidemiologic studies have examined potential etiologic factors other than tobacco and alcohol in this region of South America that may contribute to the high rates of ESCC. Some evidence suggests that high consumption of churrasco
and hot maté could be additional important risk factors [4
The median urine 1-OHPG level of the inhabitants of southern Brazil who were examined in this study (2.09 pmol/ml) was similar to those found in two other high ESCC-risk areas, namely Linxian, China (2.06 pmol/ml) [16
] and northeastern Iran (4.2 pmol/ml)[28
]. All of these concentrations are much higher than those reported for non-smoking US residents (0.23 pmol/ml)[29
]. As expected, tobacco smoking in our population had a significant association with urine 1-OHPG. Non-smoke exposed subjects who regularly prepare barbeque also had elevated urine 1-OHPG concentrations, presumably from increased smoke exposure during this activity. Surprisingly, we also 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.
Brazil is a country with recognized regional socio-economical and cultural differences. Rio Grande do Sul State has an economy based largely on agriculture and cattle production which has led to high consumption of red meat, due to relatively low prices and the availability of this product, and a preference for barbequed meat. The churrasco
maker is exposed to coal or wood smoke when preparing the meat. We did not see a significant association between urine 1-OHPG concentration and the amount of barbeque consumed, but exposure to other potentially hazardous compounds that may be present in the barbequed meat, such as heterocyclic amines, should also be investigated [30
Several epidemiologic studies in this region of South America have shown an association between maté consumption and risk of esophageal cancer [4
]. Possible reasons for this association include ingestion of carcinogens present in the unprocessed leaves of Ilex paraguayensis
, ingestion of carcinogens produced or added as contaminants during the processing of the leaves, and thermal injury to the esophageal mucosa caused by drinking maté tea at very hot temperatures. Many people in this region drink large amounts of maté at very high temperatures. In our study population, we saw a median intake (interquartile range) of 500 (100 – 1000) mls/day. Previous studies in southern Brazil have reported mean maté consumptions of 1200 and 1800 ml/day and mean temperatures measured just before consumption of 63.4 and 69.5°C [31
]. Several studies have reported that only the temperature at which maté was drunk was significantly associated with ESCC risk, while the amount of maté consumed and the temperature at which it was extracted were inconsequential [7
]. Other studies, however, reported that high temperature and a high volume of consumption were both important, and were independently associated with significantly increased risk of ESCC [4
]. Yet another study reported that duration and amount of maté consumption was consistently associated with cancer risk, but temperature was not [5
]. We did not collect information on mate temperature in this study because we had no a priori
reason to suspect that consumption temperature would affect urine 1-OHPG concentration. We also thought that without objective temperature measurements, questionnaire data concerning mate temperature would not be sufficiently reliable for meaningful evaluations.
In most studies from this region, mate consumption is considered to be an independent risk factor for esophageal cancer. The underlying mechanism, whether thermal or chemical, remain unclear. Fonseca et al
. reported that extracts of unprocessed Ilex paraguayensis
are mutagenic in bacterial assays and can cause chromosomal aberrations in human peripheral lymphocytes treated ex vivo
]. The processing of this herb for maté involves roasting the leaves over an open fire, which can lead to the formation or addition of PAHs or other contaminants. A single study of processed mate purchased in Germany reported that the leaves contained up to 461 μg/kg benzo[a]pyrene, but there were relatively low concentrations of this PAH in the prepared beverage [34
]. Differences in maté brand and the details of tea preparation might change the amount of benzo[a]pyrene in the tea. The finding of benzo[a]pyrene in maté implies, however, that elevated 1-OHPG concentrations in maté drinkers may come directly from the maté, and need not be attributed to uncontrolled confounders such as smoking. Our findings raise the possibility that PAH exposure from consumption of maté may be one cause for the previously reported association between maté drinking and ESCC risk.