London: The World Health Organisation's research arm has downgraded its classification of coffee as a possible carcinogen, declaring there isn't enough proof to show a link to cancer.
But the International Agency for Research on Cancer, or IARC, also announced in a report published on Wednesday that drinking "very hot" beverages of any kind could potentially raise the cancer risk, and it classified them as "probably carcinogenic" to humans.
In particular, it cited countries including China, Iran and those in South America, where teas such as the bitter herbal infusion mate are traditionally drunk at extremely high temperatures - above 65 or 70 degrees Celsius - considerably hotter than drinks would normally be served in cafes across North America and Europe.
"I'm not really sure why coffee was in a higher category in the first place," said Owen Yang, an epidemiologist at Oxford University who has previously studied the possible link between coffee and cancer. He was not part of the IARC expert group.
"The best evidence available suggests that coffee does not raise the cancer risk," he said. Drinking very hot beverages, however, just might.
Dana Loomis, deputy head of the IARC program that classifies carcinogens, said they began to look into a possible link after seeing unusually high rates of esophageal cancer in countries where drinking very hot beverages is common.
He said that even at temperatures below 60 degrees Celsius, hot beverages can scald the skin, and that consuming drinks at even higher temperatures could be harmful.
Loomis said very hot beverages might cause a "thermal injury" in the throat that could eventually promote the growth of tumors, but that evidence was limited. He said there wasn't enough evidence to suggest if eating very hot food might also be risky.
Other experts said that people should remain focused on the leading causes of cancers including of the esophagus and that there were more important changes they could make other than waiting for their drinks to cool.
"Quitting smoking and reducing alcohol consumption are much more significant for reducing cancer risk than the temperature of what you're drinking," said Dr Otis Brawley, chief medical officer of the American Cancer Society.
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