Sitting down with a nice cup of hot tea feels positively virtuous these days. Every time we glance up at the evening news, there’s been another scientist telling us how good tea is for our health — it’s those antioxidants! But now here comes another study with a decidedly different take — tea can be dangerous… and the danger is cancer.
Tea? Cancer? Really? The study being reported found that drinking hot tea seems to be the reason people in a certain area of northern Iran have one of the world’s highest rates of esophageal squamous cell carcinoma, an often deadly form of the disease. For the study, published in the online edition of BMJ (formerly the British Medical Journal), researchers interviewed 300 people with esophageal cancer and 571 of their healthy neighbors. All had similar backgrounds and habits — including regular tea drinking. The difference? Compared with those who drank their tea warm or lukewarm, people who drank their tea “very hot” were eight times as likely to develop cancer, and those who drank it “hot” were twice as likely. In other words, it seemed that the culprit might not be the tea — but the temperature. Well, I thought, maybe there’s hope yet for us tea drinkers.
The Clearest Risk Factor
I called the study author, Farhad Islami, MD, PhD, at the International Agency for Research on Cancer in Lyon, France, to learn more. He let me know that this particular group of Iranians were at otherwise low risk for esophageal squamous cell cancer — very few smoked and most did not drink alcohol, two very significant risk factors for that disease. The study showed that tea drinking was a common habit among all subpopulations in the region (a total of 48,500 people) and that approximately 25% of the people there drink their tea at the hottest level — about 149°F or higher. This was verified later when researchers actually measured the temperature. (“Hot” was considered to be 149°F to 158°F… and “very hot,” above 158°F.) Although researchers aren’t sure why this is a problem, they believe that the heat may trigger inflammatory processes that stimulate potentially carcinogenic compounds in the esophageal mucous membranes. Perhaps even more likely, Dr. Islami says, is the fact that high heat can damage the esophageal lining, making it less able to protect itself against carcinogens coming in from the outside world.
Okay Then, What About Coffee?
America, of course, is a land of coffee drinkers, many of whom like their brew piping hot. Based on what the tea study tells us, is there reason to worry about coffee, too? Dr. Islami says it is important to note that the type of esophageal cancer most common in the West — adenocarcinoma of the esophagus — is not the same as squamous cell carcinoma, which is the most common type of esophageal cancer in Iran and worldwide. Furthermore, while a few reports suggest that other hot beverages, including coffee, might increase esophageal cancer risk, there is little research on hot coffee specifically. So we do need more studies. In the meantime, Dr. Islami speaks to common sense. “If the issue is damage to the esophageal lining, it would be safer if people do not drink very hot coffee or tea,” he says. It takes only a few minutes or so to allow your hot beverage of choice — coffee or tea — to cool to 140°F and into the safety zone.
Farhad Islami, MD, PhD, research fellow, International Agency for Research on Cancer, Lyon, France.