Drinking very hot beverages classified “probably carcinogenic” to humans

As published by the International Agency for Research on Cancer (IARC) in The Lancet Oncology medical journal, an international Working Group of 23 scientists found that drinking very hot beverages probably causes cancer of the esophagus (“oesophagus” (British English)) in humans.

very hot beverage

The IARC is the cancer agency of the World Health Organization (WHO).

Coffee and maté

Although the study was in large part designed to evaluate the carcinogenicity of drinking coffee and maté (a traditional South American caffeine-rich infused drink), the IARC Working Group found no conclusive evidence for a carcinogenic effect of drinking coffee or maté at temperatures that are not very hot.

“These results suggest that drinking very hot beverages is one probable cause of oesophageal cancer and that it is the temperature, rather than the drinks themselves, that appears to be responsible.” — Dr Christopher Wild, IARC Director

Very hot beverages

Drinking very hot (>70°C) beverages was classified by the IARC Working Group as probably carcinogenic to humans (Group 2A), based on limited evidence from epidemiological studies that showed positive associations between cancer of the esophagus and drinking very hot beverages.

China studies in particular, along with studies in other regions where tea or maté are traditionally drunk very hot (e.g., Iran, Turkey, South America), indicated that the risk of esophageal cancer increased with the temperature at which the beverage was drunk.

Although drinking hot water and tea is standard practice in China, both as part of Traditional Chinese Medicine (TCM) and tap water sterilization, WebMD China advises people to allow their beverages to cool before drinking. TCM explains that our normal internal body temperature is 37°C, which keeps a smooth blood flow in tune with normal bodily functions. Accordingly, the benefits of drinking hot water to counteract environmental or ingested coldness can certainly be achieved while maintaining a safe distance from the very hot (>70°C) temperature range.

“Smoking and alcohol drinking are major causes of oesophageal cancer, particularly in many high-income countries. However, the majority of oesophageal cancers occur in parts of Asia, South America, and East Africa, where regularly drinking very hot beverages is common and where the reasons for the high incidence of this cancer are not as well understood.” — Dr Christopher Wild, IARC Director

Esophageal cancer

Esophageal cancer is the eighth most common cause of cancer worldwide and one of the main causes of cancer death, with approximately 400,000 deaths recorded in 2012 (5% of all cancer deaths). That said, the proportion of esophageal cancer cases that may be linked to drinking very hot beverages remains unknown.

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