New research, appearing in the International Journal of Cancer, finds an association between drinking tea at very high temperatures and the risk of developing esophageal cancer.

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New research recommends letting tea cool down before drinking it.

According to the American Cancer Society, in 2019, there will be approximately 17,650 new cases of esophageal cancer and over 16,000 people will die from it.

In terms of a person's outlook, the Society estimate that approximately 20 percent of people with esophageal cancer go on to live for 5 years after the diagnosis.

Numerous factors may raise a person's risk of developing cancer of the esophagus. These include being older than 55, being male, having acid reflux, or eating a diet high in processed meats and low in fruits and vegetables.

Some researchers have also suggested that regularly drinking very hot liquids may also raise the risk of esophageal cancer.

However, most of these studies asked the participants to remember and estimate how much tea they drank and at what temperature.

Such an approach may have biased the results. Namely, when participants have to estimate something in retrospect, recall bias may affect their answers. So, a new study aimed to rectify this by measuring tea drinking temperature objectively — i.e., in a way that did not depend on a person's memory, feelings, or opinions.

Researchers, led by Dr. Farhad Islami, the strategic director of Cancer Surveillance Research at the American Cancer Society, also wanted to study tea drinking habits prospectively rather than retroactively.

Very hot tea may raise risk by 90 percent

Dr. Islami and colleagues used data on over 50,000 people included in the Golestan Cohort Study — a "population-based prospective study" — who were 40–75 years old at baseline.

The researchers clinically followed the participants for an average period of 10.1 years, between 2004 and 2017. During this time, 317 people developed esophageal cancer.

The researchers divided tea temperature into "very hot" — meaning a temperature of over 60°C, and "cold [or] lukewarm," that is, a temperature that is or falls below 60°C.

In their analysis, the researchers also considered a "reported shorter time from pouring tea to drinking" it — that is, on a scale between 2 and 6 minutes' wait, as well as "reported preference for very hot tea drinking."

Overall, the study found that drinking 700 milliliters (ml) of "very hot" tea per day increased the chances of esophageal cancer by 90 percent compared with drinking the same daily amount of cold or lukewarm tea.

"Our results substantially strengthen the existing evidence supporting an association between hot beverage drinking and [esophageal cancer risk]," conclude the researchers.

Dr. Islami and colleagues continue, "It may thus be a reasonable public-health measure to extrapolate these results to all types of beverages, and to advise the public to wait for beverages to cool to [lower than] 60°C before consumption."

"Many people enjoy drinking tea, coffee, or other hot beverages. However, according to our report, drinking very hot tea can increase the risk of esophageal cancer, and it is, therefore, advisable to wait until hot beverages cool down before drinking."

Dr. Farhad Islami

The authors caution that scientists will need to do more research to understand the mechanisms behind this association.