The present study indicate that the tea temperatures consumption above 65°C, consumption of tea more than four times in day, consumption of tea immediately after a meal, continuous tea intake and other beverages intake raise the risk of EC.
The strong association had been observed between the frequency of tea intake in a day, the volume of tea consumption and drinking hot tea with the risk of EC in our study. The temperatures above 65°C have increased risk of EC 6.1 times. Most similar studies had reported similar results(5, 11, 12). Probably, hot drinks can cause inflammatory processes and chronic irritation of the squamous cell tissue of the esophagus. This study also showed that daily amount of tea consumption more than one liter and an increase in the frequency of tea consumption (continuous tea intake) were associated with increased risk of EC. Consumption of tea more than four times in one day increased the risk of EC 10.3 times. There are studies that had reported similar results(10, 13). It can be presumed people who consume tea more than usual, may consume it with higher temperature, which in turn stimulates the surface of the esophagus and increases the risk of EC. On the other hand, high intake of tea may lead to high intake of kinds of additives (which may be used in some industrial tea packaging), this pathway can lead to carcinogenic compounds exposures. It is suggested that some future study, can investigate about types and measures of legal and illegal additive in food products including tea. Many people have reported that regular consumption of tea may be related to the lifestyle of the people of their regions. In the present study, there was a significant relationship between race with EC risk, so that, the Turkmen race had a higher chance of developing EC, which can be related to continuous consumption of tea, high temperature of drinking tea and immediate intake of tea after meals. This study showed that consumption of tea immediately after food meals, increased the risk of EC 2.1 times; while tea intake before food meals, had not such relation. There wasn’t any association between the risk of EC and green and black tea consumption, similar studies confirmed the results of this study(14). However, some other studies had shown that green and black tea had prevention role in EC(15). Studies have shown that both black and green tea with antimicrobial, antioxidant and anti-inflammatory activities may be considered as a cancer prevention agent(5, 16). But some studies have shown that green tea is related to an increase risk of esophageal cancer, which somehow caused by consuming hot tea(17). Also in this study between the consumption of other beverages such as coffee, boiling water was significant association with the risk of EC. Some studies had reported similar results(18, 19); this result meant that some other drinks may have a role in the EC etiology. There was no significant association between the amount of drinking tea per serving and the speed of drinking tea with EC in this study. However, some studies had shown that amount of drinking tea per serving was directly related to the risk of EC(20) In this study the speed of tea drinking did not associated with the risk of EC. Also, we didn’t observed any significant association between the food habits (including preferred foods cooking method and temperature of eating foods and the speed of eating foods) with the risk of EC(20, 21). While, the American Cancer Society reports that high-temperature cooking methods (such as fried food) due to the emergence of a wide range of substances that are carcinogenic, mutagenic and the formation of high levels of polycyclic aromatic hydrocarbons, as well as high levels of heterocyclic amines, raise the risk of EC(20, 21).
The strength of this study was measuring the tea temperature intake objectively through standard infrared thermometer, also, several aspects of tea drinking were investigated; including: different types of tea intake, amount daily tea consumption, speed of tea drinking, time of tea consumption cooking habits, etc. For future research, we suggest implementing of population based longitudinal study, for obtaining more complete results.