People who regularly drink scalding hot tea are more likely to get esophageal cancer. A large-scale, long-term study by Iranian scientists now confirmed what WHO cancer experts had suspected since 2016.
There are several factors that up your risk of getting cancer. Heavy drinking, smoking and obesity can all contribute to a higher cancer risk — no surprise there. But now researchers from the Tehran University of Medical Sciences in Iran have confirmed another.
Their large-scale study showed that people who regularly drink beverages hotter than 60 degrees Celsius (140 degrees Fahrenheit) have a significantly higher risk of getting esophageal cancer.
The Iranian researchers observed and examined more than 50,000 men and women from the northern Iranian province of Golestan for 13 years, from 2004 till 2017. During this time, there were 317 cases of esophageal squamous cell carcinoma (ESCC), one of two common kinds of esophageal cancer.
Scientists found that drinking 700 milliliters or more a day of tea that was at least 60 degrees Celsius "was consistently associated with an about 90 percent increase in ESCC risk."
Risk higher in South America, Asia and Africa
The Tehran University study confirms long-standing suspicions. In 2016, the International Agency for Research on Cancer (IARC) classified drinking very hot beverages as a probable carcinogen.
The agency specifically referred to drinks hotter than 65 degrees Celsius (roughly 149 degrees Fahrenheit), and specifically to mate — a tea traditionally drunk at very high temperatures in South America, Asia and Africa.
Does that mean hot tea is as dangerous as hard liquor or cigarettes, two other factors known to increase your risk of esophageal cancer? Well, it might depend on where you live. While the Iranian study implies just that, the American Cancer Society points out that in the US, hot beverages like tea, coffee or cocoa are usually drunk at temperatures below 65 degrees Celsius.
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Experts in Germany don't view hot drinks as a standout risk, either. Thomas Seufferlein is the medical director of the Internal Medicine Clinic I at University Hospital Ulm in Baden-Wurttemberg. He has been treating patients with esophageal cancer for roughly 20 years.
His reply when asked about cases of esophageal cancer brought on by hot beverage drinking?
"Personally I have never seen that in a patient."
'Blow on your drink, don't panic'
Seufferlein says there's no point in becoming alarmed about drinking hot tea in Germany at the moment.
"Around here, people who don't drink alcohol frequently and don't smoke, but come in with esophageal cancer from drinking hot drinks are the absolute exception," the doctor told DW. "I'd say to just blow on your drink and don't panic."
It's good advice — cooler tea cannot cause the same damage as hot tea, because scalding beverages basically burn the esophagus's mucous membrane.
"With these cases, we're talking about chronic heat damage," Seufferlein explained. "The damage of a mucous membrane always leads to an attempt to repair this damage. And if I have constant repairs going on, there is more room for error as well."
When these errors occur in cell divisions, it could create mutations — and this, to put it simply, is how cancer cells are born.
Seufferlein emphasized that the exact process of how hot beverages damage the esophagus has yet to be explored. But waiting for your tea to cool down a little bit before you chug it seems to be the smart thing to do for now.