Photo: Ramesh Pathania/Mint
Photo: Ramesh Pathania/Mint

No evidence that coffee causes cancer, says WHO

Drinking very hot beverages, specifically 65C or more, probably causes cancer of the oesophagus, says WHO

After listing coffee as a “possibly carcinogenic" or cancer-causing agent for nearly 25 years, World Health Organization’s cancer agency on Wednesday said there is no conclusive evidence for the same. International Agency for Research on Cancer (IARC), however, did find that drinking very hot beverages, specifically 65°C or more, probably causes cancer of the oesophagus in humans.

After reviewing more than 1,000 studies in humans and animals, an international working group of 23 scientists convened by IARC, part of the WHO, found that there was inadequate evidence to show that drinking coffee, classified as possibly carcinogenic to humans (Group 2B) by IARC in 1991, causes cancer.

Many studies showed that coffee drinking had no carcinogenic effects for cancers of the pancreas, female breast, and prostate, and in fact, reduced risks were seen for cancers of the liver and uterine endometrium. The most important studies evaluated by IARC were epidemiological studies of people who reported their coffee drinking habits and were followed up for many years to see how many of them developed cancer and how that was related to their coffee consumption.

For more than 20 other cancers, evidence was inconclusive. The summary of the final evaluations was published in Lancet Oncology on Wednesday.

The group also evaluated the carcinogenicity of drinking maté (a traditional South American beverage) and very hot beverages.

However, the group of scientists also concluded that drinking very hot beverages was classified as probably carcinogenic to humans, moving it to Group 2A in IARC’s list of cancer-causing agents. 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 countries such as China, the Islamic Republic of Iran, Turkey and South America, where tea or maté is consumed at very hot temperatures at about 70°C, found that the risk of oesophageal cancer rose with the temperature at which the beverage was drunk.

“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 Christopher Wild, IARC director, in a press release.

The term ‘carcinogenic risk’ in the IARC Monographs series is taken to mean the probability that exposure to an agent will lead cancer in humans. The IARC Monographs Programme identifies and evaluates environmental causes of cancer in humans and to date, more than 950 agents have been reviewed and classified. IARC classifies agents in different groups as follows: Group 1 is for agents when there is convincing evidence that the agent causes cancer such as tobacco and asbestos. Group 2 includes agents with a range of evidence of carcinogenicity in humans and in experimental animals. Within this, 2A means there is limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals; 2B, there is limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals.

Group 3 means the agent is not classifiable as to its carcinogenicity to humans; Group 4 means the agent is probably not carcinogenic to humans. On Wednesday, IARC concluded that drinking coffee will now be included in Group 3.

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