Thursday, November 05, 2015

Meat eaters, beware!

International Agency for Research on Cancer (IARC) is a highly respected institution for its research on carcinogens. It is a subsidiary of the World Health Organisation (WHO) and is headquartered in Lyon, France. It employs about 300 scientists from more than 50 countries. IARC has 25 countries including India as its members.

 IARC’s Director, Dr.Christopher P.Wild is an eminent cancer epidemiologist who pioneered the concept of “exposome”. Exposome encapsulates the totality of human environmental (that is, non-genetic) exposures from conception onwards. It complements the Genome for an integrated understanding of various diseases.
IARC has classified carcinogens (substances causing cancer) into five groups. The following table represents the classification:

Group identification
Number of substances identified
Carcinogenic to humans
Probably carcinogenic to humans
Possibly carcinogenic to humans
Not classifiable as to its carcinogenicity to humans
Probably not carcinogenic to humans

For example, Ethanol in alcoholic beverages is classified under group 1, Vinyl bromide and the poisonous pesticide DDT under 2A, Naphthalene under 2B, Ampicillin and Saccharin under 3. Caprolactam is the only substance placed under group 4.

On 26 October, IARC created a sensation by releasing their findings on carcinogenicity of red meat and processed meat. The press release, inter alia, noted:

Red meat
After thoroughly reviewing the accumulated scientific literature, a Working Group of 22 experts from 10 countries convened by the IARC Monographs Programme classified the consumption of red meat as probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect.

 This association was observed mainly for colorectal cancer, but associations were also seen for pancreatic cancer and prostate cancer.

 Processed meat

Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.”

Red meat refers to all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.

 Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. Most processed meats contain pork or beef, but processed meats may also contain other red meats, poultry, offal, or meat by-products such as blood.

 Examples of processed meat include hot dogs (frankfurters), ham, sausages, corned beef, and beef jerky as well as canned meat and meat-based preparations and sauces.

This definitive identification of causal relationship between meat and cancer has naturally scared the meat industry out of its wits. (Association of meat consumption with obesity and cardiovascular ailments has been recognized for long.) The North American Meat Institute (NAMI) has furiously reacted saying that “the report defies both common sense and numerous studies showing no correlation between meat and cancer. Scientific evidence shows cancer is a complex disease not caused by single foods.” But, IARC has stood its ground.

Processed meat contains sodium nitrate which on entering the human body gets converted into nitrosamine. Nitrosamine is a known carcinogenic. Some bacteria hosted in the human alimentary canal modify some components of even unprocessed red meat into nitrosamine.

It may be noted that like processed meat, tobacco smoking and asbestos are also classified as Group 1 carcinogen. This does not, however, mean that all these pose the same quantum of cancer risk. IARC has clarified that its classifications describe the strength of the scientific evidence about an agent being a cause of cancer, rather than assessing the level of risk.

IARC has cautioned that processed meat may cause stomach cancer also though the evidence for this is not deemed conclusive as yet.

IARC is a research organization whose Mission Statement declares that its objective  is to promote international collaboration in cancer research. The Agency is inter-disciplinary, bringing together skills in epidemiology, laboratory sciences and biostatistics to identify the causes of cancer so that preventive measures may be adopted and the burden of disease and associated suffering reduced.  IARC does not, however, issue any do’s and don’ts regarding consumption of food items.

Governments are expected to educate the public regarding the risk and benefits in consuming different food items. One hopes that our government will study IARC’s recent findings and make use of them while formulating its policies and advisories. Of course, there is no need to panic. It is not that every meat-eater contracts cancer. But it is better to be well-informed about the risks.

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