A few weeks ago, my wife Elie and I enjoyed our first post-COVID vaccine Shabbat lunch with friends—a true pleasure. Dessert was served with hot tea—very hot tea—and as I sat waiting for it to cool, I pondered the following:

Jutting out into the Caspian Sea at the northeast end of Iran is Golestan, one of the 31 provinces of Iran. With a population of 1.8 million, it is a relatively rural area, heavily agricultural, with a strongly religious Muslim population. Many of the homes in Golestan are fairly primitive with outdoor plumbing and outhouses, indoor heating from stoves using coal and wood, and, not infrequently, farm animals sharing the homes of the farmers and their families.

What makes this backwater community of interest to us? Golestan has a stunningly high incidence rate of squamous cell carcinoma of the esophagus (ESCC). And when I say high, I mean high—about 100/100,000 population, in contrast to the U.S., where the incidence rate for ESCC has fallen to about 4/100,000 or even lower. This incredible rate of ESCC has drawn the attention of scientists both in Iran and at the International Agency for Research on Cancer who have been studying the possible reasons for this phenomenon.

This disease has been typically associated with cigarette smoking and alcohol use. The decline in tobacco use in the U.S. has led to a decrease in this cancer in the U.S. In Golestan, cigarette consumption is relatively low, and alcohol use is almost nonexistent due to the strict observance of Muslim religious law.

It is true that Golestanis do enjoy their hookahs. The use of tobacco in hookahs involved only a relatively minor fraction of the population, nowhere near enough to account for the ESCC rates. However, while tobacco may not have been a major problem, 17% of Golestanis reported significant opium use. This was much more common in men than women (83% versus 13%) and its use did apparently double the risk of ESCC. At least one small piece of our puzzle.

Indoor air pollution from wood burning stoves, with exposure to polycyclic aromatic hydrocarbons, the same cancer-causing byproduct as from cigarette use, was a strong possible risk factor, but careful studies indicated that this did not seem to play a role. However, poor oral hygiene with extensive tooth loss seems to be extremely common in this population and this was associated with the occurrence of ESCC. Indeed, extensive tooth loss raised the risk of ESCC by a factor of 2.3. Again, a small piece of the puzzle.

Certain unique fungi found on the food in Golestan and a search for carcinogenic viruses on the farm animals in the households both proved fruitless in explaining the huge risk of ESCC that has been observed.

So where does that leave us? The exposure that has drawn the most interest and attention about Golestan is their consumption of hot beverages. Apparently the average Golestani drinks at least a liter of hot black tea each day. It is a matter of pride to prepare it in the samovar that has been handed down as a family heirloom. They do not seem to drink any other beverages—no Coke, Pepsi or Poland Spring water. But what makes it interesting is that the tea is drunk at scalding temperatures.

Many of us will remember a lawsuit in the early 1990s when an older woman sued McDonald’s when she spilled her coffee and suffered severe burns on her thighs that required plastic surgery and much medical care. The temperature of the coffee at McDonald’s was 83-88 degrees C (boiling is 100 degrees). Just to remind you of context, normal body temperature is 37 degrees and the ambient temperature on a nice spring day is 20-22 degrees (68-71 Fahrenheit).

The average Briton prepares his/her tea at 60-65 degrees, but that is before adding milk or lemon. And it is not uncommon to blow on it or to drink from the saucer. Not so in Golestan. There it is proper etiquette to drink immediately after the tea is poured and before there has been an opportunity for the drink to cool. At least a third drink their tea at 70 degrees or more and another third in the 65-69 degree range. According to the studies conducted there, longstanding exposure to temperatures greater than 65 degrees raises the risk of ESCC by 2-3 fold, while exposure to tea at 70 degrees or more gives a risk of 8-fold or more.

There are numerous studies on body surfaces (skin, esophagus, anogenital tract) that have demonstrated that prolonged or repeated irritation or burns, followed by healing and repeated irritation and scarring can lead to proliferation of the tissue which engenders the carcinogenic process to manifest itself. Thus, it is plausible to believe that the repeated burning and healing in the esophagus that the hot tea causes could indeed be responsible for a substantial fraction of the high rates of ESCC observed there.

Tea may be good after a meal, but let’s be careful out there.

Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.

This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.