World Health Organization Downgrades Coffee as Possible Carcinogen

Nearly 25 years after declaring coffee a possible carcinogen associated with an increased risk of bladder cancer, the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC) reversed its position noting its latest review found “no conclusive evidence for a carcinogenic effect" of coffee drinking."

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 (Group 2B) by IARC in 1991. After thoroughly reviewing more than 1,000 studies in humans and animals on more than 20 different types of cancer, the international Working Group of 23 scientists found there was inadequate evidence for the carcinogenicity of coffee drinking overall. In addition, 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.

The agency did, however, issue a warning that drinking very hot beverages probably causes esophageal cancer, reaffirming WHO’s position on this issue and advice to let hot drinks cool before consuming them.

IARC noted drinking very hot beverages is now classified as “probably carcinogenic." The group based its findings on what it described as limited evidence from epidemiological studies that showed positive associations between cancer of the esophagus and drinking very hot beverages. The studies focused on places such as China and South America, where tea or maté is often consumed at temperatures of about 158 degrees Fahrenheit—roughly 10 degrees hotter than people in the United States, United Kingdom and Europe are accustomed to drinking coffee or tea.

“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," IARC Director Christopher Wild said.

In June, a study published in the journal Cancer Epidemiology, Biomarkers & Prevention found coffee consumption may decrease the risk of colorectal cancer. What’s more, the indication of decreased risk was seen across all types of coffee, both caffeinated and decaffeinated. In January, a study published in the Journal of the American Heart Association found contrary to current clinical belief, regular caffeine consumption does not lead to extra heartbeats, which, can lead in rare cases to heart- or stroke-related morbidity and mortality.