Very hot tea increases risk of esophageal cancer
When it comes to tea, the spirits divide: if one person is at a good temperature at the moment, another finds him already too cool. In view of the risk of cancer, however, it is highly recommended not to drink tea too hot. This is confirmed by a major analysis in Iran.
Photo by 五玄土 ORIENTO on Unsplash
Very hot tea can promote the development of esophageal cancer: People who regularly drink more than 0.7 litres of tea at a temperature of at least 60 degrees have a significantly increased risk of developing squamous cell carcinoma in the oesophagus. This is the result of a study conducted by Farhad Islami of Tehran University of Medical Sciences in Tehran (Iran) and presented in the International Journal of Cancer.
There have been indications of such a connection for some time. Therefore, the International Agency for Research on Cancer (IARC) classifies "drinking very hot beverages at temperatures above 65 degrees Celsius" as "possibly carcinogenic". The cancer information service of the German Cancer Research Centre (DKFZ) also warns on its website against very hot drinks in connection with esophageal cancer.
The researchers around Islami now present results on a very large database: Between 2004 and 2017, they collected data from more than 50,000 women and men in the Northern Iranian province of Golestan for their study. On average, the participants were tracked for a good ten years. In addition to the exact circumstances of tea consumption, the researchers collected socio-economic data and eating habits.
Trained employees visited the study participants in their apartments. Two cups of tea were poured to determine the preferred drinking temperature. The employee put a thermometer into a cup. When the temperature of the tea had dropped to 75 degrees Celsius, the participants were asked to drink the tea. If the tea was still too hot for them, they were again asked to drink it at 70, 65 and 60 degrees. The preferred drinking temperature was noted. In earlier studies, the participants themselves had reported how hot their tea usually is when they drink it - an error-prone process.
During the study period, there were 317 cases of squamous cell carcinoma among the participants, one of the two most common types of esophageal cancer. After adjusting for possible other influencing factors such as smoking or alcohol consumption, there were statistically clear correlations between the temperature of the tea and the risk of cancer. In addition, the shorter the time between pouring the tea and drinking it, the greater the risk of cancer.
As to the possible cause, the researchers write that the hot fluid can cause injuries that lead to inflammatory processes in the tissue of the oesophagus. In turn, the genetic material can be directly altered or the formation of carcinogenic substances can be intensified - with a tumour as a possible consequence.
Stephen Evans of the London School of Hygiene & Tropical Medicine, who was not involved in the study, also suspects heat injuries as a cause. Jam heated in the microwave is also known to cause injuries to the esophagus. "It's possible that the injury could lead to cell changes and therefore cancer." (dpa)
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