Doctors have long wondered whether very hot beverages increase the risk for squamous cell esophageal cancer. Considering the many things people eat and drink, studies have come back mixed on the hot drink and cancer connection.
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But in the Golestan Province in Iran, people tend to drink just two beverages: water and very hot tea. The people in the province also tend to have an abnormally high rate of esophageal cancer.
A research team traveled to Golestan and documented the smoking, alcohol use and tea habits of 871 people in the region, 300 of whom were recently diagnosed with esophageal cancer. According to the study published in the British Medical Journal, the researchers found a strong link between the temperature at which people preferred their tea and the likelihood that they developed cancer.
"We have found many factors and the hot tea is one of the factors," said Reza Malekzadeh, professor and director of the Digestive Disease Research Center at the Tehran University of Medical Sciences in Iran.
"Having a poor social economic status, not eating enough vegetables and fruit and not brushing their teeth are some [risk factors]. One of the main ones is the hot tea," he added.
So how hot is too hot for your throat? The scientists classified warm tea at anything below 149 degrees Fahrenheit. Hot tea, anything measured above 156 degrees Fahrenheit, doubled the risk of esophageal cancer. People who frequently had very hot tea, at 158 degrees Fahrenheit or above, had an eight-fold increased risk of esophageal cancer.
At the very hot temperature, Malekzadeh said, "it would even hurt your finger -- but they get used to it, you see."
"The temperature -- this is probably a cultural type of thing," he added.
Hot tea is not the only beverage linked to esophageal cancer. Drinking alcohol and using tobacco also ups the risk for cancer in the windpipe.
But unlike booze and cigarettes, Malekzadeh said evidence in his study showed it's not the chemicals in the tea that matters.
"It doesn't seem to be that," he said. "Especially this specific type of cancer -- the so called squamous cell cancer."
Past studies comparing adjacent tea drinking areas in Linxian, China and areas surrounding the Golestan province in Iran, showed temperature affects cancer rates, according to data cited in Malekzadeh's article. Esophageal cancer numbers rose in regions where people preferred their tea very hot, and dropped where tea was served at a cooler temperature.
But gastroenterologists aren't entirely convinced of hot tea's effects. Dr. Jennifer Christie, an assistant professor in the Division of Gastroenterology at Emory University School of Medicine in Atlanta, said she's not making any new recommendations to her patients yet.
"I think it's an important study and it clearly adds to our knowledge about esophageal cancer," said Christie. "But I would not tell people to stop drinking hot tea at this point. Also there's diet, and you have to look at genetic factors that are involved, as well."
Christie said esophageal cancer, especially the squamous cell variety, is much more prevalent in Asian and South American countries than in the United States.
"So there's not a recommended screening for esophageal cancer in the U.S.," she said.
Instead, Christie said U.S. doctors perform esophageal testing based on symptoms.