Drinking scalding-hot tea may increase esophagus cancer risk

Tea drinkers who love a scalding-hot cup of the beverage may want to let it cool down a bit to avoid an increased risk of oesophagus cancer, a new study suggests. 

Among tea drinkers followed for about 10 years, those who drank a lot of tea and liked it very hot — above 60ºC — had nearly double the risk for oesophageal squamous cell carcinoma compared to those who drank cooler tea and less tea in general, researchers report in the International Journal of Cancer. 

“Drinking hot tea is a very common habit worldwide, and earlier studies have pointed to an association between drinking hot beverages and an increased risk of oesophageal cancer,” study leader Dr Farhad Islami of the American Cancer Society (ACS) in Atlanta, Georgia, said by e-mail. 

Oesophageal squamous cell carcinoma is the sixth most common cause of cancer death worldwide. In the US, according to the ACS, the lifetime risk of developing the disease is about 1 in 132 in men and about 1 in 455 in women. 

The World Health Organisation’s International Agency for Research on Cancer has classified drinking “very hot” beverages, above 65oC, as “probably carcinogenic” to humans. 

Starting in 2004, researchers collected data on 50,000 adults living in the Golestan Province in northeastern Iran, where high rates of oesophageal cancer have been reported and where residents drink an average of 1,100 millilitres of black tea daily. 

Early in the study, researchers poured cups of tea during interviews with participants to measure tea drinking temperatures and asked each person about their preferences for tea temperature, as well as how soon after pouring the tea they tended to drink it. 

By 2017, 317 participants had developed oesophageal squamous cell carcinoma. People who regularly drank tea at temperatures of 60ºC or higher were 41 per cent more likely than those who drank it cooler to develop oesophageal cancer. Those who preferred “very hot” tea had nearly two-and-a-half times the risk of those who liked it cold or lukewarm. And those who drank their tea within two minutes of pouring it had 51 per cent higher risk than those who waited six minutes or more. 

Overall, people who drank at least 700ml daily at temperatures above 60ºC had 91 per cent higher risk than those who drank less tea, at lower temperatures. 

“We are not asking people to stop drinking tea, but we recommend waiting a while until hot beverages cool down before drinking,” Islami said. 

Even after researchers accounted for factors that could affect the risk of oesophageal cancer, including use of tobacco, alcohol or opium, and sociodemographic factors, the heightened risk with scalding-hot tea remained. 

“This is probably the first well-designed and informative study that actually went to people to measure the temperature, while most previous studies were based on self-reports,” said Dr Dirk Lachenmeier, a food chemist and toxicologist at the Chemical and Veterinary Investigation Agency in Karlsruhe, Germany. “Would you know the temperature of your coffee this morning?”

Although more research is needed, the most likely reason for the increased cancer risk is a direct influence on throat tissues through consistent inflammation, said Lachenmeier, who was not involved in the research.

New studies are also investigating serving temperatures in restaurants and cooling behaviours, such as using milk, he noted.

“Food serving establishments might, for example, change temperatures to lower default settings,” he said in an email. “In coffee, very often brewing is done at too high temperatures, which is also bad for the taste of the beverage.”