Coffee no longer comes with cancer; it may actually prevent it

Despite brimming data showing that drinking coffee can be good for your health, there has been a lingering black stain on the popular drink’s reputation—the 1991 assessment by the World Health Organization that classified coffee as a possible carcinogen. However, that stain got scrubbed away. In a recent announcement and an accompanying article in the journal The Lancet Oncology, the WHO reversed that 1991 classification, striking coffee from the Group 2b list of foods and beverages that are “possibly carcinogenic to humans.” That initial classification was based on “limited evidence of an association with cancer of the urinary bladder from case-control studies, and inadequate evidence of carcinogenicity in experimental animals.” According to 23 health experts who met in May to review more than 1,000 new and old human and animal studies on coffee, that limited evidence didn’t stand up. The experts concluded that coffee is a Group 3 agent, which is “not classifiable as to its carcinogenicity to humans.” Moreover, amid their review, the experts also noted that several studies provided evidence that coffee drinking may reduce the risk of cancers of the liver and uterine endometrium. For more than 20 other types of cancers, the effect of coffee drinking was inconclusive, the experts found. The WHO’s new assessment aligns with the American Institute for Cancer Research, which also lists coffee as a beverage that may protect against endometrial and liver cancers. Other research on coffee has found that the beverage can lower a person’s risk of cardiovascular disease, liver diseases, diabetes, and an overall risk of dying too soon. When the WHO experts looked back at the studies that did finger coffee as a cancer-causer, they found some troubling weaknesses. Namely, “positive associations reported in some studies could have been due to inadequate control for tobacco smoking, which can be strongly associated with heavy coffee drinking,” the experts wrote. Similarly, the experts reviewed data on maté, a strong caffeinated drink particularly popular in South America. That beverage was also moved to Group 3 from a Group 2A classification of “probably carcinogenic to humans.” However, not everything in the WHO review was good. The experts also found evidence that drinking extremely hot beverages of any kind—even water—may cause cancer. “Epidemiological evidence for very hot beverages and human cancer has strengthened over time,” the authors wrote. New studies have found that drinks at or above 65°C/149°F can act as tumor promoters. “Although the mechanistic and other relevant evidence for very hot beverages is scant, biological plausibility exists for an association between very hot beverages and cell injury and the sequelae that might lead to cancer,” they concluded. As such, they classified beverages at or above 65 degrees Celsius/149 degrees Fahrenheit as Group 2A, “probably carcinogenic to humans.” In the US, standard coffee serving temperatures range from 70 to 85 degrees Celsius (158 to 185 degrees Fahrenheit). In a 2008 study, researchers found that around 60 degrees Celsius/140 degrees Fahrenheit was the ideal drinking temperature for coffee.