Influence of the mode of coffee preparation
According to a Swedish study with 64,603 participants, including 3,034 cases – the first study to look at the influence of coffee preparation on cancer risk – the risk of cancer could vary between drinkers of filtered or boiled coffee100:
- For all sites combined, as well as for prostate and colon alone, there was no association between mode of coffee preparation and cancer risk.
- For breast cancer, 4 cups or more of boiled coffee per day compared to 1 or fewer decreased the risk by 48%.
- An increased risk was found in pre-menopausal and a decreased risk in post-menopausal women for total and filtered coffee, respectively.
- The consumption of boiled coffee increased the risk of pancreatic cancer in both sexes, and of cancer of the respiratory tract in men.
IARC also stated that “studies that have been reported do not show consistent and robust differences in cancer risk for different kinds of coffee or different preparation methods”1.
Influence of the temperature of hot beverages
In 2016, an IARC Monographs Working Group reviewed research to reach conclusions as to the carcinogenic hazard to humans of drinking coffee, mate, and very hot beverages. They assessed more than 1,000 observational and experimental studies that investigated the association between cancer at more than 20 sites with drinking coffee, mate, and very hot beverages1.
They classified beverages consumed at very high temperatures (defined as over 65°C) in Group 2A: “probably carcinogenic to the human oesophagus”1. 65°C is significantly hotter than the temperature at which most people can comfortably drink coffee without scalding their mouth and tongue18,19; coffee is typically drunk at temperatures below 60°C. When IARC assessed evidence for a link between oesophageal cancer and coffee specifically, it found insufficient evidence of an association.
A further paper published in 2018 supported the IARC view, suggesting that their results corroborate the epidemiological observations about a probable oesophageal cancer risk caused by drinking very hot drinks101.
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