A research division of the World Health Organization said Monday that bacon, sausage and other processed meats cause cancer, and that red meat probably does, too.
The report by the influential group stakes out one of the most aggressive stances against meat yet taken by a major health organization, and it is expected to face stiff criticism in the United States.
The WHO conclusions are based on the work of a 22-member panel of international experts that reviewed decades of research on the link between red meat, processed meats and cancer. The panel reviewed animal experiments, studies of human diet and health, and cell mechanisms that could lead from red meat to cancer.
The panel’s decision was not unanimous
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But the panel’s decision was not unanimous, and by raising lethal concerns about a food that anchors countless American meals, it will be controversial. The $95 billion U.S. beef industry has been preparing for months to mount a response and some scientists, including some unaffiliated with the meat industry, have questioned whether the evidence is substantial enough to draw the kinds of strong conclusions that the WHO panel did.
We simply don’t think the evidence supports any causal link between any red meat and any type of cancer.
Shalene McNeill, executive director of human nutrition at the National Cattlemen’s Beef Association
“We simply don’t think the evidence supports any causal link between any red meat and any type of cancer,” said Shalene McNeill, executive director of human nutrition at the National Cattlemen’s Beef Association.
The research into a possible link between eating red meat and cancer — colorectal cancer is a longstanding area of concern — has been the subject of scientific debate for decades. But by concluding that processed meats cause cancer, and that red meats “probably” cause cancer, the WHO findings go well beyond the tentative associations that other groups have reported.
The American Cancer Society stops short of telling people that the meats cause cancer
The American Cancer Society, for example, notes that many studies have found “a link” between eating red meat and heightened risks of colorectal cancer. But it stops short of telling people that the meats cause cancer. Some diets that have lots of vegetables and fruits and lesser amounts of red and processed meats have been associated with a lower risk of colorectal cancer, the American Cancer Society tells the public, but “it’s not exactly clear” which factors of that diet are important.
Moderate evidence suggests an association between the increased intake of processed meats (e.g., franks, sausage, and bacon) and increased risk of colorectal cancer and cardiovascular disease.
The Dietary Guidelines for Americans, the federal government’s advice compendium
Likewise, the Dietary Guidelines for Americans, the federal government’s advice compendium, encourage the consumption of protein foods such as lean meats as part of a healthy diet. Regarding processed meats, however, the Dietary Guidelines do offer a tentative warning: “Moderate evidence suggests an association between the increased intake of processed meats (e.g., franks, sausage, and bacon) and increased risk of colorectal cancer and cardiovascular disease,” the guidelines say. The Dietary Guidelines stop well short of saying processed meats cause cancer, however.
In recent years, meat consumption has been the target of multi-faceted social criticism, with debates erupting not just over its role on human health, but the impact of feedlots on the environment and on animal welfare. The public debate over the WHO’s findings will likely play out in political lobbying, and in marketing messages for consumers.
But at its core, the dispute over meat and cancer revolves around science, and in particular the difficulty that arises whenever scientists try to link any food to a chronic disease. “Is everything we eat associated with cancer?” a much noted 2012 paper in the American Journal of Clinical Nutrition asked.
That paper reviewed the academic studies conducted on common cookbook ingredients. Of the 50 ingredients considered, 40 had been studied for their impact on cancer. Individually, most of those studies found that consumption of the food was correlated with cancer. When the research on any given ingredient was considered collectively, however, those effects typically shrank or disappeared.
Should we all just become vegetarians?
In an announcement that has alarmed bacon lovers and sent the beef industry into a furor, the World Health Organization's cancer research arm Monday declared processed meat a carcinogen, like tobacco, and said red meat is probably one, too. Here's what experts have to say about what this new warning means for your diet:
Q: What meats are they talking about exactly?
A: The International Agency for Research on Cancer's definitions of processed meat and red meat are very wide. Processed meats encompass any meats that have been “transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation.” This would include sausages, corned beef, hot dogs, beef jerky, canned meat, meat-based preparations and sauces, turkey and chicken cold cuts, as well as bacon.
Q: Why do they think these are dangerous to our health?
A: Scientists think that something bad happens to meat during the process of salting, curing or other treatment that causes the buildup of carcinogenic chemicals such as N-nitroso-compounds (NOC) and polycyclic aromatic hydrocarbons (PAH) in the food. In red meat, cooking can also produce suspected carcinogens — in this case heterocyclic aromatic amines (HAA) and PAH.
Q: Oh-oh. I eat a lot of meat. What do I do now?
A: The IARC's director, Christopher Wild, said that the group's findings support recommendations to “limit” intake of meat. But Wild also hedged a bit saying that red meat has “nutritional value.”
The American Cancer Society's Susan Gapsur recommends that people who do eat meat begin to cut back on the amount of red meat they consume and “really limit” their intake of processed meat. Gapsur, a vice president for epidemiology, said people should be moving toward a more plant-based diet and choose fruits, vegetables, and beans as alternatives to meat.
Marion Nestle, a professor of nutrition, food studies and public health at New York University, said her recommendation on processed meat and red meat the same: Eat less. But Nestle stops short of recommending everyone should become a vegetarian. “Some people are interpreting it as don't eat meat at all. I don't know if that's reasonable,” she said. “The evidence against processed meat is very strong, but it's very hard to consider giving up. A BLT is really a wonderful thing.”
Q: What's a safe level of meat consumption? Is it okay for me to eat a hamburger with bacon twice a week? Once a week? Once a month?
A: While scientists have come up with those sorts of general recommendation for alcohol consumption (one drink a day), none exists for meat. A person's individual biology is complex and a safe level for one person may not be safe for another. It depends on what the rest of your diet looks like, how often you exercise, your genes and a whole slew of other factors.
ARIANA E. CHA, The Washington Post