WHO cancer agency: ‘Very hot beverages’ can probably cause cancer in humans

Very hot beverages consumed at more than 65°C can probably cause cancer of the esophagus, according to the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO). Based on limited evidence from human and animal studies, IARC classified very hot beverages as Class 2A – probably carcinogenic to humans. The classification only evaluates the potential of a substance to cause cancer and does not indicate the level of risk to people’s health, according to the agency.

 

Dr. Thomas G. Sherman, Associate Professor, Department of Pharmacology and Physiology, Georgetown University Medical Center (webpage):

Expertise: Nutrition, metabolism and endocrinology

“Studies over the past 4–10 years have narrowed the list of suspected dietary habits associated with the incidence of esophageal cancer. These studies originally focused on specific ingredients within beverages, such caffeine in coffee. Several of these studies, including a recent meta-analysis, however, focused on a common factor for all such beverages: they can be very hot, and the question was asked whether recurring thermal injury to the esophagus may be the real risk factor for esophageal cancer.

“Explanations for how thermal injury can increase the risk of esophageal cancer vary and include both potential genetic and metabolic processes. For example, a series of studies have independently identified a specific unusual pattern of mutations in the TP53 gene associated with esophageal cancers in countries where the link to drinking very hot beverages is the strongest, such as in Lower Normandy, France, Northern Iran, and Southern Brazil.

“An alternative (and attractive) explanation focuses on the important barrier function that the cells lining the surface of the esophagus play in protecting tissues from exposure to potential carcinogens in foods and the air. Repeated thermal injury to this barrier might permit otherwise insignificant levels of food-borne carcinogens, such as alcohol or air-borne components of tobacco, that would normally pass through the digestive system or airways undetected, to impact exposed sensitive tissues.

“The observation that the consumption of very hot beverages is a risk factor for esophageal cancer is quite relevant, but the possible explanations for this increased risk await further research. The International Agency for Research on Cancer (IARC) has classified very hot beverages as a Group 2A carcinogen, meaning that very hot beverages are one probable cause of esophageal cancer.

“This classification conveys no information on risk, however. According to a thorough 2015 meta-analysis in BMC Cancer, the odds ratio (OR) of hot beverages and esophageal cancer for men or women was 2.36 and 2.45, respectively. This means that the risks for esophageal cancer are roughly 2.40 times higher if you drink very hot beverages compared to those who do not drink very hot beverages. Fortunately, this is 2.40 times a very small number; as an absolute cancer risk, very hot beverage consumption is very low compared to known carcinogens, including alcohol.”

 

Dr. Robert Schiestl, Professor of Pathology, Environmental Health
and Radiation Oncology, UCLA Schools of Medicine and Public Health (webpage):

Expertise: Carcinogenesis, DNA damage and repair, toxicology, gene-environment interactions

“I have worked on lethal heat and genetic instability previously and found that lethal heat causes genetic instability in yeast, and that DNA repair deficient cells that are sensitive to oxidative stress are also much more sensitive to lethal heat shock (1). The same will happen in your esophagus, which is what is first hit by the elevated temperature other than the tongue. And tongue cancer is very rare. It is also known that burns increase inflammation and oxidative stress, both are involved in carcinogenesis and increase the risk of cancer. These are repeatedly, every day happening oxidative stress bursts that over time cause cancer. In addition to the oxidative stress caused by heat, heat causes cell injury and inflammation takes place to repair the injury caused by the heat. This inflammation causes secondary oxidative stress that leads to further increase in the risk of cancer.”

(1) Davidson JF, Schiestl RH. Cytotoxic and genotoxic consequences of heat stress are dependent on the presence of oxygen in Saccharomyces cerevisiae. J Bacteriol. 2001 Aug;183(15):4580-7

 

Declared interests (see GENeS register of interests policy):

Dr. Thomas G. Sherman: “I have no associations, financial or otherwise, with any of this research or with companies investigating or treating cancer. My interests are purely in nutrition.”

 

Reference:

Carcinogenicity of drinking coffee, mate, and very hot beverages‘ by Dana Loomis et al, published in The Lancet on Wednesday, June 15, 2016.

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