The current study was designed to determine whether drinking yerba maté results in significant exposure to polycyclic aromatic hydrocarbons, including known carcinogens such as benzo[a]pyrene. The concentrations of 21 individual polycyclic aromatic hydrocarbons were determined in the dry leaves of eight commercial brands of yerba maté, as well as in infusions made with two commonly used brands and hot (80 degrees C) or cold (4 degrees C) water. Infusions were made by adding the hot or cold water to the leaves, steeping for 5 minutes, removing and storing the resulting infusion, and then adding more of the same temperature water to the remaining leaves. This infusion process was repeated 12 times for each temperature. Any polycyclic aromatic hydrocarbons released into these infusions (ng/g of dry leaves) were measured in the first, third, sixth and twelfth infusions and were estimated for the other eight. The total concentrations of the 21 polycyclic aromatic hydrocarbons in the dry leaves of the different brands of yerba maté were found to range between 536 ng and 2906 ng per gram of leaves. Benzo[a]pyrene concentrations varied from 8.03 ng/g to 53.3 ng/g of dry leaves. For the infusions prepared using Brand One and hot water, 37% (1092 ng out of 2906 ng) of the total measured polycyclic aromatic hydrocarbons in the dry leaves and 50% (25.1 ng out of 50 ng) of the benzo[a]pyrene content were released into the 12 infusions. For the maté infusions prepared using Brand One and cold water 34% (999 ng out of 2906 ng) of the total polycyclic aromatic hydrocarbons content of the dry leaves and 56% (28.1 ng out of 50 ng) of the benzo[a]pyrene content were released into the 12 infusions. Brand Two yielded similar results. The authors conclude that very high concentrations of carcinogenic polycyclic aromatic hydrocarbons are found in yerba maté leaves, and substantial portions of these compounds are released into hot and cold maté tea infusions. Furthermore, the results suggest that levels of benzo[a]pyrene intake associated with drinking maté may be comparable to that associated with smoking cigarettes, and they support the theory that the carcinogenicity of yerba maté may be related to its polycyclic aromatic hydrocarbons content.

The current case-control study was designed to evaluate the association between maté intake and bladder cancer. Maté is a type of tea made from Ilex paraguariensis which is widely consumed in South America as maté con bombilla and maté cocido. Drinking maté has previously been found to be linked to the risk of esophageal, oral, lung, and bladder cancers. 114 Argentinean case-control pairs were interviewed regarding their maté consumption at the time of interview and at points 20 and 40 years previously. Regular maté con bombilla consumption 20 years earlier was found to be strongly associated with bladder cancer in ever-smokers (odds ratio=3.77, 95% confidence interval: 1.17–12.1), but not in never-smokers. Maté cocido was not found to be associated with bladder cancer. The authors note that these results are consistent with a previous study in Uruguay.

The current cross-sectional study was designed to examine the effect of drinking yerba maté during pregnancy on the risk of preterm and small-for-gestational-age (small) birth. Yerba maté, a hot infusion of Ilex paraguayensis, is widely consumed in Southeast Latin America, including during pregnancy. All 5,189 mothers who gave birth to single children during 1993 at the hospitals in Pelotas, Brazil were interviewed during the first 24 hours after delivery. Gestational age at birth was determined using the Dubowitz score and birth weight was also recorded. The incidence of small birth was 8.0% and preterm birth was 9.1%. Maté consumption of at least once per week during the entire pregnancy was reported by 68% of the new mothers. Crude analyses demonstrated a 30% increase in the risk of small birth for daily maté drinkers compared to nonconsumers (prevalence ratio = 1.3; 95% CI 1.1–1.6), whereas no statistical association was found for preterm births. After controlling for confounding factors, the significance of the association with small-for-gestationa-age birth no longer held and the lack of association with prematurity remained unchanged. The authors conclude that the common practice of daily maté drinking during pregnancy had no harmful effect on intrauterine growth or duration of pregnancy.

This retrospective hospital-based case-control study was designed to evaluate the role of maté consumption on the risk of esophageal cancer. Including 344 cases with squamous cell carcinoma of the esophagus and 469 controls, the study took place at the Oncology Institute of Montevideo, Uruguay, between January 1988 and August 2000. Maté intake was found to be significantly associated with an increased risk of esophageal cancer. The association showed a clear dose response, with a relative risk of 2.84 [95% confidence interval (CI), 1.41–5.73] for those drinking more than one liter per day of maté compared to nondrinkers. Cases who reported drinking maté at a very hot temperature had an almost two-fold increase in risk [OR 1.87; 95% CI, 1.17–3.00] compared to those drinking warm to hot maté. Maté amount and temperature were found to have independent effects and (although no departure from multiplicativity was found between the two covariates) those drinking more than one liter per day of maté at a very hot temperature had a three-fold increase in risk (OR 2.95; 95% CI, 1.30–6.74) compared to those drinking under half a liter per day of maté at a warm to hot temperature. Cases with high cumulative intake of maté in the presence of low alcohol and tobacco exposures had a lower-risk estimate (OR, 1.52; 95% CI, 0.88–2.62), whereas those with high cumulative consumption of maté, alcohol, and tobacco were found to have a seven-fold increase in esophageal cancer risk (OR, 7.10; 95% CI, 3.75–13.46). The authors conclude the report by noting that the population-attributable fraction as a result of maté consumption was calculated at 53%, of which the sole effect of amount and temperature were 14.8% and 12.6% respectively, and 14.9% was attributable to high maté intake at high temperatures.

Maté is a local tea prepared with infusions of the herb Ilex paraguariensis. The current case-control study was designed to determine the relationship between maté consumption and the risk of lung cancer in Uruguay. The study, which included 497 cases of lung cancer and 497 controls, was carried out at the Instituto de Oncologia, Montevideo, between 1988 and 1994. Maté consumption has been associated with increasing risk of most upper-aerodigestive tract cancers. After adjusting for major cofactors, including pack-years of cigarette smoking, maté intake was found to be associated with a 1.6-fold increase in risk of lung cancer for heavy drinkers compared to light drinkers, and was found to have a significant dose-response pattern. When the analysis was refined to include cell type, small cell lung cancer was found to have a significant increase in relative risk for maté intake (odds ratio = 2.9; 95% confidence interval, 1.3-6.2) and maté duration (OR = 3.6; 95% CI, 1.3-9.9). On the other hand, pulmonary adenocarcinoma was not found to be associated with maté drinking.