Cancer preventionIn vitro and animal experiments have shown a protective effect of Mate against cancer. Several studies have been conducted on the anticancer properties of Mate tea and comparisons have been made with other teas such as green tea, believed to have high anticancer potential (Yamamoto and others 1997). Tests conducted by Ramirez-Mares and others (2004) on in vitro chemopreventive activity included cytotoxicity, TPA-induced ornithine decarboxylase (ODC), quinone reductase (QR) activities using HepG2 cells, and topoisomerase inhibitory activity using Saccharomyces cereviseae. These tests are of particular importance because cytotoxicity is highly associated with anticancer activity. ODC is a promoter of tumor growth and tumor cells often contain high concentrations of ODC. QR is another screening method for anticancer activity and topoisomerase is required for mitosis; cancer cells show higher concentrations of topoisomerase II (Topo II) than normal cells due to high rates of cell division. Mate was shown to possess the highest cytotoxicity against human liver cancer cells compared to green tea, IC50 value of 12.01 g eq. (+) catechin/mL for Mate compared with 72 g eq. (+) catechin/mL for green tea. Table 5 shows the concentrations of tea needed for various inhibitory activities on HepG2 cells.
Table 5—. Inhibitory effect of Mate tea, green tea, and Ardisia tea against growth of HepG2 cancer cells.a
| ||μg eq. (+) catechin/mL ± SD|
|IC10|| 9.3 ± 0.6|| 50.7 ± 2.5|| 4.9 ± 1.4 |
|IC50|| 12.0 ± 0.2|| 72.0 ± 1.8|| 46.9 ± 3.3 |
|IC90||17.6 ± 0.8||113.6 ± 5.5||177.2 ± 33.4|
Human antitopoisomerase II activity was significant and showed a 65% inhibition compared with 15% for green tea (Ramirez-Mares and others 2004). The catalytic topoisomerase inhibition, however, was only on TopoII and not topoisomerase I (Topo I). An in vitro study on oral cell carcinoma showed that concentrations greater than 375 μg of solid extract/mL had complete inhibition of cancer cell growth (Gonzalez de Mejia and others 2005). Mate has shown to be a potent TopoII inhibitor and thus showing significant cancer cell growth inhibition, even at low concentrations.
Proteasome inhibitors are an important aspect of cancer research (Osanai and others 2007). The compound epigallocatechin gallate (EGCG), found in green tea, has already been shown to inhibit proteasomes (Osanai and others 2007). Similarly, compounds have been identified in Mate that show proteasome inhibition (Arbiser and others 2005). The compounds identified were 3,5-dicaffeoylquinic acid (3,5-DCQ), 5-caffeoylquinic acid (5-CQ), and 3,4-dicaffeoylquinic acid (3,4-DCQ), which act by inhibiting the chymotrypsin-like activity of a purified 20S proteasome and 26S proteasome in Jurkat T (human, peripheral blood, leukemia) cell extracts. Among all of these compounds, 3,5-DCQ showed the highest inhibitory ability. It is believed to act similarly to EGCG due to its similar structure (Arbiser and others 2005).
Other compounds found in Mate have also been studied for their chemopreventive properties. Rutin and quercetin are two that show distinct cytotoxicity to HepG2 cells (Alía and others 2006). Although these compounds are found with small concentrations in Mate they show the diversity of flavonoids present in Mate that contribute to its anticancer potential.
Epidemiological studies There has been a growing concern over the fact that there are some epidemiological studies that suggest an association between Mate consumption and increased risk of developing certain cancers, namely, esophageal, oral, lung, bladder, renal, and other cancers of the head and neck (Pintos and others 1994; De Stefani and others 1996, 1998; Goldenberg and others 2003; Bates and others 2007). These incidences have been highly correlated to regions in which heavy Mate consumption persists, portions of Brazil and Uruguay. However, it is also recognized that other habitual factors may play a role, such as smoking and alcohol consumption, which are strongly associated with the culture of these regions. Goldenberg (2002) and Goldenberg and others (2003, 2004) report of epidemiological studies showing increased rates of squamous cell carcinoma with increased Mate consumption even when other confounding factors such as smoking were present. The results of these studies indicate that consuming more than 1 L of Mate a day can increase the risk for head and neck cancer by 3 to 5 times, as well as an apparent association to lung cancer (Vassallo and others 1985; De Stefani and others 1996; Sewram and others 2003). It was also reported that consuming strong and very hot tea can increase the risk for oral cancer. Consuming other hot beverages, coffee and green tea, also increased this risk by 2 to 4 times. Thus, the measured risk of oral cancer may be due to thermal injury (Rolon and others 1995; Castellsague and others 2000). With respect to bladder cancer, again epidemiological studies by the same leading authors (De Stefani and others 1991) conducted in Uruguay showed that a relationship between Mate and bladder cancer was found when associated with smoking and to some degree in nonsmokers as well, though less defined. In the same study, it was also shown that consumers of black tea and coffee had an increased risk of bladder cancer. An epidemiological study conducted in Argentina showed an increase risk of bladder cancer in Mate drinkers and smokers but not in nonsmokers (Bates and others 2007). Whether this increased risk of bladder cancer is due solely to Mate alone, smoking alone, a combination of both, or solely another cause is unclear.
It should also be noted that the case studies of Mate consumption and increased cancer incidence also include individuals that consume black tobacco and alcohol, namely, wine. De Stefani and others (1988) stated that there is a correlation to the increased risk of oral cancers in those individuals who consume wine, Mate, and smoke. This increase is also noted to be greater in those who smoke black tobacco over blond tobacco. Again, there is no direct implication that any one factor contributes more to this increase in oral cancers. Due to these other confounding factors, Mate may not be a carcinogen on its own but, due to the high temperature at time of consumption, may in fact be a means of increasing absorption for the carcinogens found in cigarette smoke and other environmental contaminants that are carcinogens or cancer promoters (Goldenberg and others 2004).
On the other hand, there may be compounds present in Mate that could contribute to cancer. Fagundes and others (2006) have shown a correlation between the amount of Mate consumed and the amount of polycyclic aromatic hydrocarbons (PAHs) in the body. It is known that PAHs, particularly benzo[a]pyrene, have carcinogenic properties and that tobacco smoke and grilled meat contain high concentrations of PAHs; at least 15 PAH compounds have been found in Mate varieties. These compounds were isolated and identified by the utilization of stir bar sorptive extraction (SBSE) and high-performance liquid chromatography–fluorescence detection (HPLC–FLD) (Zuin and others 2005). Total PAHs found in various Brazilian Mate samples ranged from 600 to 2300 ng/L, with naphthalene, acenaphthene, and phenanthrene having the highest concentrations. Table 6 shows the PAH compounds identified in Mate and their average concentration in 11 Mate samples.
Table 6—. Average concentration of polycyclic aromatic hydrocarbons found in Brazilian Mate tea samples.a
|Naphthalene|| 96.5||Benzo(a)anthracene|| 9.7|
|Fluoranthene|| 61.4||Indeno(1,2,3)pyrene|| 9.5|
|Pyrene|| 59.1||Benzo(g,h,i)perylened|| 7.7|
|Anthracene|| 50.9||Dibenz(a,h)anthracene|| 5.0|
|Fluorene|| 29.7||Benzo(k)fluoranthene|| 3.6|
|Benzo(a)pyrene|| 12.2|| |
It is known that exposure to PAHs through tobacco smoke and other sources may increase the risk of esophageal squamous cell carcinoma (ESCC). Fagundes and others (2006) evaluated 200 healthy adult Mate tea consumers, half male and half female with half being smokers and half being nonsmokers, to determine the concentrations of 1-hydroxypyrene glucuronide (1-OHPG), a PAH glucuronide detoxification metabolite excreted in the urine. Their presence provides evidence that an individual has been exposed to PAHs. 1-OHPG can be measured in the urine using immunoaffinity chromatography, synchronous fluorescence spectroscopy, and a urine cotinine dipstick test; the tests were conducted by the Natl. Cancer Inst. at Johns Hopkins Univ. This study found that there was a direct correlation between the amount of Mate consumed and the concentrations of PAHs in the urine, the higher the consumption the higher the concentrations. Table 7 shows the increasing concentrations of 1-OHPG in the urine with increasing Mate consumption.
Table 7—. Concentration of 1-hydroxypyrene glucuronide (1-OHPG) in urine of humans.a
|Mate consumption (mL/day)||1-OHPG (pmol/mL)|
However, other than an increase in Mate consumption alone, higher concentrations of 1-OHPG can also be correlated with a combination of smoking and Mate drinking. When Mate consumption is combined with smoking, 1-OHPG concentrations are significantly higher but Mate alone produces about the same concentrations of 1-OHPG on average as smoking alone (Fagundes and others 2006). When examining a population in Campinas, SP, Brazil and the coffee and Mate they consumed, PAHs were found in all products and ranged from 10.12 μg/kg for coffee to 0.70 μg/kg for Mate (Rojo de Camargo and others 2002). Considering the per capita average daily consumption estimates in Brazil of 69.79 g of Mate tea, one can assume that Mate tea contributes with approximately 0.05 μg of total PAHs to the dietary intake of these contaminants by the studied population (n= 600) (Rojo de Camargo and others 2002).
Although there has been no proven biological correlation to the drinking of Mate and developing cancer (Pereira Jotz and others 2006), the contamination with PAHs does present a plausible explanation for increased rates of Mate drinking and cancer. It is highly probable that PAHs are obtained in the processing, as Mate is commonly dried over a smoky wood fire. The smoke from the wood may thus be producing the PAHs found in Mate. There also appears to be an apparent lack of new information on the subject. Though a number of papers are published on the topic, no new evidence has been presented. This is an area that warrants further investigation.