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| United Nations |
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 today 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
emphasized. "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 five per cent 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.
The working group also found that cold maté did not
have carcinogenic effects in experiments on animals or in epidemiological
studies. Therefore, drinking maté at temperatures that are not very hot was not
classifiable as to its carcinogenicity to humans.
That finding was based on inadequate evidence in
humans for the carcinogenicity of drinking cold or warm maté and inadequate
evidence in experimental animals for the carcinogenicity of cold maté as a
drinking liquid.
In addition, the group found that drinking coffee was
not classifiable as to its carcinogenicity to humans. The large body of
evidence currently available led to the re-evaluation of the carcinogenicity of
coffee drinking, previously classified as possibly carcinogenic to humans by
International Agency for Research on Cancer in 1991.
After reviewing more than 1,000 studies in humans and
animals, the working group found that there was inadequate evidence for the
carcinogenicity of coffee drinking overall. Many epidemiological studies showed
that coffee drinking had no carcinogenic effects for cancers of the pancreas,
female breast and prostate, and reduced risks were seen for cancers of the
liver and uterine endometrium.
For more than 20 other cancers, the evidence was
inconclusive, according to the working group.
The working group's evaluation is in line with
the WHO Technical Report Series 916 on Diet, Nutrition and the Prevention of
Chronic Diseases, which states that people should not consume drinks when they
are at a scalding hot temperature.
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