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Hot reaction to WHO report on cancer, red meat

News Roundup from the November 2015 issue of Canadian Cattlemen

Predictably red meat got another black eye when the World Health Organization’s International Agency for Research on Cancer (IARC) report linking red and processed meats and cancer was released in the Lancet journal last month.

Overall, the IRAC working group of 22 scientists from 10 countries classified consumption of processed meat as “carcinogenic to humans” (Group 1) on the basis of sufficient evidence for colorectal cancer. Additionally, a positive association with the consumption of processed meat was found for stomach cancer. They also classified consumption of red meat as “probably carcinogenic to humans” (Group 2A).

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In response, the Canadian Cattlemen’s Association noted IARC conducts hazard assessments, not risk assessments. “That means it considers whether meat at some level, under some circumstance could pose a risk.

“IARC has found hazards in about half of the agents it has reviewed,” says the CCA.

In reaching the 2A classification, the working group’s review of 800 existing epidemiological studies from around the world “concluded that there is limited evidence in human beings for the carcinogenicity of the consumption of red meat.”

Colorectal cancer was its principle focus relative to red meat and a meta-analysis of colorectal cancer in 10 cohort studies reported a statistically significant dose — response relationship, with a 17 per cent increased risk per 100 grams per day of red meat.

The CCA says the American Society of Clinical Oncology (ASCO) estimates a person with an average risk of colorectal cancer has about a five per cent chance of developing colorectal cancer so if that person consumed 100 grams of red meat per day that would increase his or her risk of developing colorectal cancer by just under one per cent.

Current industry estimates peg average Canadian consumption at 50 grams of fresh red meat. “Accordingly, if there is an increase in the potential risk of colorectal cancer from red meat consumption, by these estimates it is small and must be considered relative to the very significant nutritional benefits that red meat provides,” says the CCA statement.

While red meat’s nutritional benefits were not considered directly in this evaluation, the report did note “red meat contains high biological value proteins and important micronutrients such as B vitamins, iron (both free iron and haem iron), and zinc.”

The World Health Organization has previously stated that two billion people — over 30 per cent of the world’s population — have anemia, many due to iron deficiency.

Beef is among the best food sources of well-absorbed iron. Meat has long provided an important source of nutrients for Canadians and the industry takes pride in providing high-quality beef products to consumers.

There are many theories why red and processed meat may be linked to cancer however, it’s important to note that no scientific consensus has been reached.

When it comes to processed meats the WHO working group lumped processed pork and beef and ham into its Group 1 list along with tobacco, asbestos and diesel fumes as a cancer risk.

The North American Meat Institute (NAMI) termed the report dramatic and alarmist. In a statement the industry association said, “classifying red and processed meat as cancer ‘hazards’ defies both common sense and numerous studies showing no correlation between meat and cancer and many more studies showing the many health benefits of balanced diets that include meat. Scientific evidence shows cancer is a complex disease not caused by single foods and that a balanced diet and healthy lifestyle choices are essential to good health.”

“It was clear sitting in the IARC meeting that many of the panellists were aiming for a specific result despite old, weak, inconsistent, self-reported intake data, said NAMI vice-president of scientific affairs, Dr. Betsy Booren. “They tortured the data to ensure a specific outcome.

“Red and processed meat are among 940 agents reviewed by IARC and found to pose some level of theoretical ‘hazard.’ Only one substance, a chemical in yoga pants, has been declared by IARC not to cause cancer,” said Dr. Booren.

“IARC says you can enjoy your yoga class, but don’t breathe air (Class I carcinogen), sit near a sun-filled window (Class I), apply aloe vera (Class 2B) if you get a sunburn, drink wine or coffee (Class I and Class 2B), or eat grilled food (Class 2A). And if you are a hairdresser or do shift work (both Class 2A), you should seek a new career.

“IARC’s decision simply cannot be applied to people’s health because it considers just one piece of the health puzzle: theoretical hazards. Risks and benefits must be considered together before telling people what to eat, drink, drive, breathe, or where to work,” she said.

National Beef Cattle Association beef checkoff nutrition scientist and registered dietitian, Shalene McNeill says the 22 experts on the IARC were unable to reach complete consensus on their report and had to settle for a majority agreement.

“Cancer is a complex disease that even the best and brightest minds don’t fully understand,” said McNeill. “Billions of dollars have been spent on studies all over the world and no single food has ever been proven to cause or cure cancer. The opinion by the IARC committee to list red meat as a probable carcinogen does not change that fact. The available scientific evidence simply does not support a causal relationship between red or processed meat and any type of cancer.”

A large meta-analysis, published online in May in the Journal of the American College of Nutrition, analyzed the relationship between red meat intake and risk for colorectal cancer and concluded “red meat does not appear to be an independent predictor of CRC risk,” according to Dr. Dominik Alexander, the epidemiologist who conducted the research on behalf of the beef checkoff.

“There are a constellation of factors that are associated with the probability of getting cancer, which include age, genetics, socio-economic characteristics, obesity, lack of physical activity, where you grew up, alcohol consumption, smoking and even your profession,” says Alexander. “The bottom line is the epidemiologic science on red meat consumption and cancer is best described as weak associations and an evidence base that has weakened over time. And most importantly, because red meat is consumed in the context of hundreds of other foods and is correlated with other behavioural factors, it is not valid to conclude red meat is an independent cause of cancer.”

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