why hot tea doesn’t actually double your risk of cancer

If you like your tea nice and hot, you may be worried about misleading popular science headlines telling you that you’re doubling your risk of cancer. You’re not. But you’ll still want to pay attention to the research.

outdoor tea kettles
Photo by Soroush Karimi

Another day, another study about something common potentially causing cancer. This time, the danger is hot tea, which seems a little strange because last we heard, tea prevents some types of cancer. So, you might be wondering, what happened to turn tea into a carcinogen? Is this a replay of the debacles with bacon and coffee? Well, not exactly. The issue isn’t the tea itself, but the temperature at which it’s consumed according to the researchers, who posit that damage from drinking extremely hot tea on a regular basis can trigger the development of esophageal cancer as shown by a sample of 50,045 people between 40 and 75 years of age in northeastern Iran followed for just over ten years on average.

Now, first and foremost, what exactly do we mean by extremely hot tea? Based on regional habits, the study considers anything over 140 °F, or 60 °C, to fit the bill. Russians, Turks, Iranians, and some Central Asian countries often drink tea much hotter than that, making them ideal for studying the hypothesis that boiling tea leads to cancer, and the results are scary to say the least. Subjects drinking more than 700 ml, or three cups, of broiling hot tea per day were 90% more likely to be diagnosed with it than those who either drank less, or let the temperature drop to a more comfortable level.

Does this mean that you better cut down on your hot tea or make sure it’s below the study’s threshold for excessive heat or you’ll get esophageal cancer? Not necessarily. Out of more than 50,000 participants, just 317 new cases were diagnosed over roughly three years. Since cancer can have many causes and there may have been many other factors involved, this may be too few subjects for any definitive result, especially when we consider just how many things may potentially exacerbate cancer risk, like significant alcohol consumption and smoking, both of which are known factors in esophageal cancer. But interestingly enough, this is not the first time a link between drinking very hot tea and cancer has been demonstrated.

An effort in 2009 led by the same lead investigator, studying the same province, and with a similar number of participants also showed a serious increase in risk and a similar number of esophageal cancer cases. But again, noting that there may be many other factors at play, the study limits its conclusions to saying that daily damage to the esophagus by drinking three or more cups of really hot tea is associated with an elevated chance of a cancer diagnosis, not that hot tea itself causes cancer. When we consider the numbers, the absolute risk of developing this form of cancer is low, less than one percent in the studied population. But if you’re going to drink lots of tea and have other risk factors for esophageal cancer, maybe wait for your drink to cool a bit and have one less cup.

See: Islami, F., et. al., (2019) A prospective study of tea drinking temperature and risk of esophageal squamous cell carcinoma, IJC, DOI: 10.1002/ijc.32220

Islami, F., et. al., (2009) Tea drinking habits and esophageal cancer in a high risk area in northern Iran: population based case-control study, BMJ, DOI: 10.1136/bmj.b929

# health // cancer / cancer risks / medical research

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