A new report from the World Health Organization's International Agency for Research on Cancer offers some good news for coffee drinkers: it concludes that the beverage is unlikely to increase cancer risk - it may actually reduce it. However, the report also found that consuming very hot drinks could raise the risk of esophageal cancer.
Researchers from across 10 countries - including Mariana Stern, associate professor of preventive medicine and urology at the University of Southern California - publish their findings in The Lancet Oncology.
The carcinogenic effects of coffee consumption were last evaluated by the International Agency for Research on Cancer (IARC) in 1991.
That review deemed drinking coffee as "possibly carcinogenic to humans," after identifying "limited evidence" of a link between consumption of the beverage and bladder cancer.
However, the IARC note that there have been numerous studies assessing the effects of coffee consumption over the past 25 years, and such studies may explain the previous link with bladder cancer, which prompted a new review.
Coffee consumption linked to lower risk of some cancers
The new review concluded that, overall, there is "inadequate evidence" to suggest that coffee consumption increases the risk of cancer.
The majority of studies showed coffee consumption does not increase the risk of cancers of the pancreas, breast, and prostate.
Additionally, the review found that drinking a cup of coffee each day may
The link between coffee consumption and 20 other cancers was inconclusive, according to the review.
The IARC say the new findings do not mean their last review was wrong to conclude a possible link between coffee consumption and bladder cancer, but that more studies are now available to conclude that the previously identified risk was due to other factors, such as smoking.
Drinking beverages at 65°C or higher may cause esophageal cancer
While the review drew some positive conclusions about coffee intake, it also concluded that consuming very hot beverages - including coffee and yerba maté - is "probably carcinogenic to humans."
The researchers found that drinking any beverage at a temperature of 149°F (65°C) or higher may raise the risk of esophageal cancer - a form of cancer that begins in the esophagus, the muscular tube that links the throat to the stomach.
The team notes that in certain countries in South America, such as Argentina, Uruguay, and Paraguay, it is common practice to consume yerba maté at temperatures between 150-212°F (66-100°C).
Interestingly, these countries also have high rates of esophageal cancer, and the reasons for this have not been well understood.
The new review suggests that drinking very hot beverages may play a role, especially after finding no association between consuming cold or warm yerba maté and increased cancer risk.
"We were now able to evaluate more carefully the effect of maté itself from the effect of temperature, and we concluded that the observed links between maté drinking and cancer of the esophagus seem to be largely driven by drinking maté very hot. Similar associations are seen for other very hot beverages, like tea or coffee."
Stern adds that there is physical evidence that very hot beverages can damage the cells lining the esophagus, and this may contribute to cancer development.
Based on the results of the review, Stern offers a word of advice when it comes to drinking hot beverages: "Enjoy your coffee or maté, but make sure it's not very hot."