LONDON Drinking hot tea may cause throat cancer, Iranian researchers said Friday, suggesting people should let steaming drinks cool before consuming them.
Previous studies have linked tobacco and alcohol with cancer of the oesophagus, and the research published in the British Medical Journal suggests that scalding beverages may also somehow pave the way for such tumors.
Drinking very hot tea at a temperature of greater than 70 degrees Celsius was associated with an eight-fold increased risk of throat cancer compared to sipping warm or lukewarm tea at less than 65 degrees, the researchers said.
Reza Malekzadeh of Tehran University of Medical Sciences and colleagues studied the tea-drinking habits of 300 people with oesophageal cancer and another 571 healthy men and women from the same area in Golestan Province in northern Iran.
That region has one of the highest rates of throat cancer in the world but smoking rates and alcohol consumption are low, the researchers said. Nearly all the volunteers drank black tea regularly, consuming on average more than a liter each day.
People who regularly drank tea less than two minutes after pouring were five times more likely to develop the cancer compared to those who waited four or more minutes, the researchers said.
British studies have reported people prefer their tea at an average temperature of 56 degrees to 60 degrees, they noted.
It is not clear how hot tea might cause cancer but one idea is that repeated thermal injury to the lining of the throat somehow initiates it, researchers said.
Cancers of the oesophagus kill more than 500,000 people worldwide each year, with the bulk of the disease occurring in discrete populations in Asia, Africa, and South America. The tumors are especially deadly, with five-year survival rates of 12 to 31 percent.
Earlier this week, U.S. and Japanese researchers reported that about a third of East Asians -- Chinese, Japanese and Koreans -- have an enzyme deficiency that puts them at higher risk of developing oesophageal cancer when they drink alcohol.