What the WHO? Global health agency flip-flops on coffee.
Twenty- five years after declaring one of the most consumed beverages in the world was “possibly carcinogenic to humans,” the World Health Organization’s cancer agency has officially downgraded coffee’s cancer risk, saying an exhaustive review of the available science could find no conclusive evidence of harm.
Unless it’s drunk super hot.
According to 23 experts assembled by the International Agency f or Research on Cancer ( IARC), which last year decreed eating hotdogs and other processed meats caused cancer, said drinking “very hot beverages” at temperatures above 65 C probably causes cancer of the esophagus, one of the deadliest cancers.
That conclusion is based on epidemiological studies in China, Iran, Turkey and South America, where tea or maté, an infusion of the dried leaves of a shrub native to South America, is traditionally served extremely hot — hot enough to burn the tongue. Those studies showed an increased risk of esophageal cancer the higher the temperature.
Wh e n the experts weighed the evidence for coffee alone, however, they found no clear indication of risk associated with coffee drinking overall.
“This means simply that the data did not permit a conclusion either that it is safe or that it is dangerous,” Dr. Dana Loomis, deputy head of the IARC monographs program, said in a briefing from Paris.
The working group reviewed more than 1,000 studies in humans and animals. For 20 different cancers, the evidence was “inconclusive.” However many studies showed coffee probably doesn’t increase the risk of breast and prostate cancer, and may significantly lower the risk of endometrial and liver cancers.
In 1991, coffee was thought a possible cause of bladder cancer. The re- think means it moves down the agency’s list of potential carcinogens, from category 2b (“possibly” carcinogenic to humans) to group 3 (“not classifiable as to carcinogenicity”).
Loomis said the science on coffee has become larger and stronger since 1991, and older studies in the 1970s linking coffee with bladder cancer could have been because of smoking or other biases.
While “very hot” drinks are probably carcinogenic, Loomis said that’s based on studies conducted in countries where tea and maté are consumed at temperatures around 70 C, or about 10 degrees hotter than people in North America and Europe “typically want their tea or coffee,” he said.
Jack Siemiatycki, a prominent cancer epidemiologist at the University of Montreal, said IARC decisions aren’t taken as gospel by the scientific community.
“They are taken as the opinions of 20 or 25 people who gathered for a week in Lyon (who) looked at the evidence and interpreted it one way,” he said.