Setting aside the popular belief that coffee is mainly carcinogenic, a WHO panel has concluded that all hot beverages including hot water are carcinogenic and cause cancer but interestingly drinking them as cold beverages was not found to be carcinogenic.
The panel, a global Working Group of 23 scientists convened by the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), has evaluated the carcinogenicity of drinking coffee, maté, and other very hot beverages and classified them as probably carcinogenic to humans (Group 2A).
Studies in places such as China, Iran, Turkey, and South America, where tea or maté is traditionally drunk very hot (at about 70 °C), found that the risk of oesophageal cancer increased with the temperature at which the beverage was drunk.
However, the panel found no conclusive evidence for a carcinogenic effect of drinking coffee but they did find that drinking very hot beverages probably causes cancer of the oesophagus in humans, while no conclusive evidence was found for drinking 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,” says Dr Christopher Wild, IARC Director.
The study showed that there is positive association between cancer of the oesophagus and drinking very hot beverages. These experiments involving animals, showed limited evidence for the carcinogenicity of very hot water.
Usually, smoking and alcohol drinking are major causes of oesophageal cancer, particularly in many high-income
countries but the majority of oesophageal cancers occur in parts of Asia, South America, and East Africa, where regularly drinking very hot beverages is common, said Dr Wild.
Oesophageal cancer is the eighth most common cause of cancer globally and 400 000 deaths were recorded in 2012 (5% of all cancer deaths). The study was published in The Lancet Oncology, and the detailed assessments will be published as Volume 116 of the IARC Monographs.