WHO agency’s study deems processed meats like bacon as carcinogenic
Red and processed meats have the potential to cause cancer in humans, according to a report by a World Health Organization agency that is drawing ire from meat industry groups that argue the science is inadequate.
The determination, published by a panel of researchers for the International Agency for Research on Cancer in a medical journal Monday, classifies processed meat products like salami and bacon carcinogenic to humans, the strongest level of risk for cancer, and a category shared with tobacco smoke and diesel engine exhaust.
Fresh meats like steaks and roasts are considered probably cancer-causing, a level of risk shared with the widely used herbicide glyphosate.
The IARC, considered an authority in evaluating evidence on cancer causation cited studies that conclude there is strong evidence to support a link between eating too much meat and the onset of colorectal cancer, the third-most common type world-wide.
“On the basis of the large amount of data and the consistent associations of colorectal cancer with consumption of processed meat across studies in different populations, which make chance, bias, and confounding unlikely as explanations, a majority of the Working Group concluded that there is sufficient evidence in human beings for the carcinogenicity of the consumption of processed meat,” according to the report, which appears in the Lancet Oncology.
The processed meat classification was based on evidence linking consumption with colorectal and stomach cancer, while the red meat classification took into account the positive associations with colorectal, pancreatic and prostate cancer, said the authors in the report.
The IARC report confirms the previous recommendations of expert committees. The World Cancer Research Fund in 2011 concluded that there is strong evidence that both red and processed meat increases the risk of colorectal cancer, advising that humans eat no more than 500 grams a week of meats like beef, pork and lamb, and that they limit consumption of products like ham and salami as much as possible.
“The link to cancer is supported by increasingly compelling research,” wrote MarionNestle, a professor of nutrition, food studies and public health at New York University who wasn’t involved in the IARC report, in an email. “There seem to be many reasons to eat less beef, climate change among them, but cancer is a more personal worry.”
The results by the 22-person panel, which consisted of scientists from 10 nations, already have drawn criticism from meat and food industry groups that have braced for such decisions for years, in part by funding research on the benefits of eating meat.
The conclusions by the agency “defy both common sense and dozens of studies showing no correlation between meat and cancer and other studies showing the many health benefits of balanced diets that include meat,” said the North American Meat Institute, a Washington, D.C., group that represents and lobbies for meat and poultry producers likeTyson Foods Inc. and JBS USA, a division a Brazilian meatpacker JBS SA, in a statement issued Friday.
“It was clear sitting in the IARC meeting that many of the panelists were aiming for a specific result despite old, weak, inconsistent, self-reported intake data,” said Betsy Booren, NAMI Vice President of Scientific Affairs, in a statement. “They tortured the data to ensure a specific outcome.”
The meat industry has battled international and U.S. health authorities on the place of meat in a balanced diet for decades, most recently in the U.S. Department of Agriculture and Health and Human Service’s Dietary Guidelines for Americans, which serve as a benchmark for the agencies’ nutrition education and food-assistance programs.
Environmental, animal welfare and public health groups have long advised that consumers avoid meat for its effects on health and the environment, while meat companies have promoted the food staple’s positive attributes, including its protein, vitamin and iron content.
Shalene McNeill, director of human nutrition at the National Cattlemen’s Beef Association, served as an observer at the researchers’ meeting in Lyon, France in October.
“The bulk of evidence really hinged around observational studies” said Dr. McNeil, which she argues had a “limited ability to disentangle the other factors that could be contributing to an outcome” including exercise, smoking or other components of a subject’s lifestyle.
“Cancer is a serious disease that we don’t want to take lightly, but correlation is not causation,” said Dr. McNeill, explaining that the association between eating meat and cancer could be attributed to those other factors. The nutritionist pointed to recent research, in part funded by the beef industry, that has concluded the evidence supporting an association between meat and cancer is weakening.
Dr. McNeill also said there could be “unintended consequences” of people cutting meat out of their diet.
“When people cut back on a food they don’t necessarily replace it with broccoli,” she said.
Susan Gapstur, vice president of epidemiology for the American Cancer Society says the Atlanta-based group also recommends Americans limit intake of those meats, based on the link to colorectal cancer, noting that evidence on association with other types of cancer is more limited.
The risk assessment “simply cannot be applied to people’s health because it considers just one piece of the health puzzle: theoretical hazards,” said the Meat Institute’s president Barry Carpenter, adding that “risks and benefits must be considered together.”
“There is no group that could convince the meat industry that the science is definitive on the link to cancer, because the playbook of every industry under attack is to instill doubt in the evidence,” said Bonnie Liebman, director of nutrition at the Washington, D.C., Center for Science in the Public Interest, which advises consumers to minimize meat consumption.