WHO: Cold Coffee Served Lukewarm

26. July 2016

Following the efforts of the WHO's special department in putting processed meats under the microscope, hot drinks are now the topic. Coffee and tea, contrary to earlier judgements, are suddenly no longer carcinogenic. The question remains open: how dangerous is it to rehash old studies?

Harmless or carcinogenic – the International Agency for Research on Cancer (IARC), an institution of World Health Organisation, is dealing with such issues. Last year, publications on cancer risk associated with meat provided for headlines.

It’s no isolated instance: already in 1991 IARC experts had classified coffee drinks as “possibly carcinogenic”. Mate preparations – they concluded – were even seen as being “probably carcinogenic”. Thermal lesions increase the risk of squamous cell carcinoma. The ingredients were also subject to criticism. There is “limited evidence” of bladder cancer in humans, it was stated.

IARC oncologists work with five categories here: “carcinogenic to humans” (Group 1), “probably carcinogenic” (Group 2A), “possibly carcinogenic” (Group 2B) “no classification” (Group 3) and “probably not carcinogenic “(group 4).

Hot brewed and drunk cold

Due to its social relevance – the majority of people consume foods, soups and drinks at temperatures between 55 and 70 degrees Celsius – researchers dug into the topic again. In Lancet Oncology they back-pedalled in large part. Researchers analysed nearly 500 epidemiological studies of different scope, methodology and quality which appeared since the earlier classification of hot drinks. On this basis, scientists no longer classified coffee and mate beverages, prepared European style, as “possibly carcinogenic”.

“The new evaluation ended up in Group 3, ie, ‘unclassifiable’: This means the IARC found no convincing evidence of an association of daily coffee consumption with increased risk of cancer in people”, explains Professor Dr. Gerhard Eisenbrand from the Technical University of Kaiserslautern, Germany.

“On the contrary, a reduced risk of individual cancers stands out”. The IARC mentions liver cancer and cancer of the endometrium. “However, with other types of cancer, there have even been recent indications of a reduced risk, for example, of cancer of the bladder, the oesophagus, and the prostate, which is something which needs further investigation”, Eisenbrand goes on to add.

The current evaluation was surprising. Last year, Chinese scientists led by Weixiang Wu arrived at different results. They analysed cohort studies and case-control studies involving a total of 250,000 participants. There’s a very likely statistical significance here between coffee intake and the risk of bladder cancer was demonstrated. Smokers who drank coffee fared slightly better.

Oesophagus with hot flash

Based on their evaluation, IARC scientists do not share this assessment. At the same time they warn about very hot food, which can lead to oesophageal cancer. “The majority of people worldwide consume solid foods, soups and drinks at a temperature of 55 to 70 degrees Celsius”, says Professor Dr. Daniel Palmes from University Hospital Muenster, Germany. “Several prospective-randomised trials and meta-analyses have clearly demonstrated the link between hot food and drinks and an increased number of new cases of oesophageal cancer”. As evidence, he cites publications in BMC Cancer and in American Journal of Preventive Medicine.

If the barrier function of the squamous oesophagus is damaged and carcinogenic substances such as nitrosamines, tobacco or alcohol enter the picture, the risk of malignant diseases rises. Palmes: “Coffee in contrast in this respect can even have a protective effect through its high polyphenol content, which acts with antioxidative and anti-inflammatory – and over the long term possibly anticarcinogenic – effects”. What’s more Eisenbrand makes mention of desirable effects. In his view the aromatic beverage is associated with reduced risk of chronic diseases, such as type 2 diabetes. “Numerous other studies – from cell culture to controlled human intervention studies – support the view that coffee consumption is more associated with health protection than with adverse impacts”.

The gist of the matter

But how relevant are the results actually? Professor Dr. Ute Nöthlings from the University of Bonn makes mention of important carcinogens: “Smoking remains one of the major modifiable risk factors for bladder cancer”, Nöthlings says. “With oesophageal cancer, in addition to smoking the consumption of alcohol is one of the known preventable risk factors”. At the same time science can lose much of its credibility. First risky, then suddenly harmless – this is something which can be difficult to convey to lay persons. Key messages, such as the idea to not consume scalding hot food and drinks, have been left by the wayside.

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Medicine, Oncology, Research

1 comment:

The problem is that extrapolating numbers from epidemiology is not possible. Unless there is scientific proof backed up by evidence from pathology. Without that it is just numbers. Then you come up with just scaremongering. Like saying omega three supplements are associated with prostate cancer.
I have never taken epidemiology seriously.
Life gives you cancer.

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