Scratch coffee off the list of possible carcinogens, declared the World Health Organization (WHO) in a June 15, 2016 monograph published in The Lancet. However, “very hot” beverages probably do pose a cancer risk, WHO added.
In 1991, WHO’s cancer agency—the International Agency for Research on Cancer (IARC), in Lyon, France—had classified coffee as “possibly carcinogenic to humans” based on limited evidence from case control studies that coffee was associated with bladder cancer.
However, many of those early studies may have confounded coffee drinking with smoking, which is a major risk factor for bladder cancer—and because coffee drinking and smoking often go together, IARC noted.
Also, new and better research on coffee and cancer has come to light in the past 25 years. The members of the IARC’s Working Group who developed the monograph had more than 1,000 observational and experimental studies to comb through.
“For many cancer types, we found clear evidence that coffee is not carcinogenic. In fact, we found that coffee protects against some cancers such as liver and uterine endometrium cancer,” said Mariana Stern, PhD, a member the Working Group and an Associate Professor of Preventive Medicine and Urology at University of Southern California’s Keck School of Medicine, in Los Angeles, CA.
Too Hot to Handle
However, IARC members also concluded that drinking beverages hotter than 149° F (65° C) is “probably carcinogenetic to humans.” This classifies piping-hot drinks in the same risk category as DDT, frying food at high temperatures, consumption of red meat, and the human papillomavirus.
This warning about “very hot” beverages stems from studies on hot tea and maté (an infusion made from dried leaves consumed mainly in South America). Locals in parts of South America, Asia, the Middle East, and Africa commonly consume tea or maté at very high temperatures—from 150° F to just below the boiling point of 212° F (65° to 100° C)—often through metal straws.
Most Americans don’t face this danger because they generally consume coffee and other hot drinks at around 140° F (60° C), according to the National Coffee Association. However, McDonald’s—which was famously sued over a spilled cup of coffee that burned an elderly woman—reportedly serves its coffee at temperatures of 170° to 180° F (77° to 82° C).
“Consumers should take a common sense approach,” the National Coffee Association advises. “If it’s too hot on your lips, it’s too hot to swallow.”