Hot Tea May Raise Esophageal Cancer Risk
It's Not the Tea; It's the Temperature -- Scalding Hot Liquid Could Injure Cells in Esophagus, Study Says
March 26, 2009 -- Drinking hot or very hot tea may make a certain type of esophageal cancer more likely.
That news appears in the advance online edition of BMJ, formerly called the British Medical Journal.
Researchers studied tea drinkers in northern Iran's Golestan province, which has a high rate of esophageal squamous cell carcinoma.
That's the world's most common type of esophageal cancer. But it's not the type of esophageal cancer that's been rising in Western countries (that's adenocarcinoma of the esophagus).
Why study tea drinkers in northern Iran? Because just about everyone there drinks tea daily, and some esophageal cancer risk factors, like smoking tobacco and drinking alcohol, aren't common.
Hot Tea, Higher Risk
The Iranian tea study comes from researchers including Farhad Islami, a research fellow at Tehran University of Medical Sciences.
They interviewed 300 people with confirmed cases of esophageal squamous cell carcinoma, as well as 571 healthy people of similar backgrounds.
Participants answered questions about their tea-drinking habits, including how hot they usually drank their tea (very hot, hot, warm, or lukewarm) and how long they let the tea brew before drinking it.
Nearly all participants -- 98% -- said they drank black tea daily.
Esophageal cancer was eight times as common among people who drank "very hot" tea, compared to warm or lukewarm tea drinkers. By the same comparison, hot tea drinkers were twice as likely as warm or lukewarm tea drinkers to have esophageal cancer.
The findings held regardless of other risk factors. But what's "hot" to one person may be "lukewarm" to someone else.
So Islami's team checked data from more than 48,000 local people who were served tea and indicated their preferred tea temperature, which was checked by a digital thermometer.
The findings: 39% drank their tea at temperatures less than 60 degrees Celsius (140 degrees Fahrenheit), 39% drank their tea at 60-64 degrees Celsius (140-147 degrees Fahrenheit), and 22% drank their tea at 65 degrees Celsius (149 degrees Fahrenheit) or higher.
Cooling Off Period
Observational studies, like this one, don't prove cause and effect. So it's not certain that hot or very hot tea caused esophageal cancer, or whether all hot drinks might have the same effect.