Your favourite brews, coffee and maté, recently got the third degree: The International Agency for Research on Cancer (IARC)—the cancer agency of the World Health Organization (WHO)—has reviewed research on the carcinogenicity of coffee, maté, and very hot drinks. They’ve concluded that drinking drinks above 149°F is “probably carcinogenic to humans.” Drinking coffee, however, may have gotten a pass: While coffee was designated as “possibly carcinogenic to humans” in 1991 by the IARC, the agency now says that, overall, they have found inadequate evidence that coffee is carcinogenic. Their findings, detailed below, were recently published in the Lancet Oncology.

• Very hot drinks. Limited evidence from epidemiological studies on hot drinks showed an association between drinking very hot drinks and an increased risk of oesophagus cancer. In particular, studies from Iran, China, Turkey, and South America, where tea or maté is consumed at very hot temperatures (around 158°F), found that the risk of oesophagus cancer increased relative to the drink’s temperature. Animal study results also suggested that drinking water above 149°F may have promoted oesophagus tumour growth.
• Maté. There is little research on drinking maté at lower temperatures; however, one study did find that drinking cold maté was not associated with an increased risk of oesophagus cancer. The IARC has concluded that there is inadequate evidence to support the carcinogenicity of drinking maté that is not very hot.
• Coffee. After reviewing over 1,000 observational and experimental studies on coffee, some of which controlled for potential confounders, like tobacco and alcohol consumption, the IARC found inadequate evidence for the carcinogenicity of drinking coffee overall. Specifically, they found no associations between drinking coffee and increased risks of pancreas, female breast, or prostate cancers. Drinking coffee was associated with reduced risks of liver and uterine endometrium cancers. The evidence was inconclusive for other types of cancers.

Source: Lancet Oncology