An international working group of scientists convened by the World Health Organization (WHO) has concluded that coffee should no longer be considered a carcinogen, although it found limited evidence that drinking very hot beverages can cause oesophageal cancer.
A summary of the final evaluations by the working group – which was convened by the International Agency for Research on Cancer, the cancer agency of WHO – was published (15/06/16) in The Lancet Oncology, and focused on the carcinogenicity of drinking coffee, maté and very hot beverages.
‘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,’ said Dr. Christopher Wild, Director of the International Agency for Research on Cancer.
The working group found no conclusive evidence for a carcinogenic effect of drinking coffee. However, the experts did find that drinking very hot beverages probably causes cancer of the oesophagus in humans. No conclusive evidence was found for drinking maté at temperatures that are not very hot.
Specifically, drinking very hot beverages was classified as probably carcinogenic to humans. This was based on limited evidence from epidemiological studies that showed positive associations between cancer of the oesophagus and drinking very hot beverages.
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.
In experiments involving animals, there was also limited evidence for the carcinogenicity of very hot water.
‘Smoking and alcohol drinking are major causes of oesophageal cancer, particularly in many high-income countries,’ Dr. Wild emphasised. ‘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.’
Oesophageal cancer is the eighth most common cause of cancer worldwide and one of the main causes of cancer death, with approximately 400,000 deaths – or 5% of all cancer deaths – recorded in 2012. The proportion of oesophageal cancer cases that may be linked to drinking very hot beverages is not known.