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 esophagus 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 60 degrees Celsius (140 degrees Fahrenheit) - had nearly double the risk for esophageal 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 esophageal cancer,” study leader Dr. Farhad Islami of the American Cancer Society (ACS) in Atlanta, Georgia, said by email.
Esophageal squamous cell carcinoma is the sixth most common cause of cancer death worldwide.
The World Health Organization’s International Agency for Research on Cancer has classified drinking “very hot” beverages, above 65 C, 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 esophageal cancer have been reported and where residents drink an average of 1,100 milliliters (about 37 ounces) 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 esophageal squamous cell carcinoma. People who regularly drank tea at temperatures of 60 degrees C or higher were 41 percent more likely than those who drank it cooler to develop esophageal 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 percent higher risk than those who waited six minutes or more.
Overall, people who drank at least 700 ml (24 ounces) daily at temperatures above 60 C had 91 percent 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 esophageal 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 wasn’t involved in the research.
New studies are also investigating serving temperatures in restaurants and cooling behaviors, 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