The World Health Organization has revised its health guidelines around the consumption of meat. The report from the WHO’s International Agency for Research on Cancer now labels processed meats as “carcinogenic to humans,” meaning their consumption can cause cancer. The report also classifies red meat as “probably carcinogenic to humans.”
What counts as red meat? What counts as processed meat?
Red meat is any meat that comes from a mammal. That means meat from cows (beef and veal), pigs (pork), sheep (lamb and mutton), horses, goats and bison all count as red meat.
White meats come from fish and poultry. The color difference is dictated by the amount of blood in the tissue, which plays into why red meat is more likely to cause cancer.
Processed meats are any meats that aren’t fresh. People typically think of processed meat as only referring to pork and beef, but this category can also include poultry (chicken, turkey, duck) and fish. A processed meat has been modified from its natural state, either through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. As the Washington Post states, “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.”
What does cancer “link” versus cancer “cause” mean?
The word “caused” sounds much more definitive than “linked.” Consider, for example, the news headlines surrounding the new report. Technically, meat consumption has been linked to cancer, especially colorectal cancer, for years. It’s a correlation or “link” backed by statistical evidence. Large-scale studies from Europe, Australia, Japan and the
U.S. have shown that people who consume more processed and red meat are more likely to develop cancer. Meanwhile, research in the lab has shown scientifically, in rat models and human cells, how that meat leads to the chemical shifts and genetic mutations that turn healthy cells into cancer cells.
Based on this collective evidence, the WHO panel has concluded that processed meat can cause cancer, upgrading its threat assessment from correlative to causal. In contrast, red meat without processing remains a probable cancer-causing agent, because there is less evidence in humans showing that it can spawn cancer.
How does processed meat compare to smoking and other carcinogens?
To classify carcinogenic status, the WHO uses five groups:
Group 1 – carcinogenic to humans
Group 2A – probably carcinogenic to humans
Group 2B – possibly carcinogenic to humans
Group 3 – not classifiable
Group 4 – probably not carcinogenic
Of the millions of chemicals in the world, the WHO only considers the 118 members of group 1 to definitively cause some form of cancer. This group includes tobacco smoke, asbestos, aflatoxins (a chemical sometimes found in organic peanut butter), coal emissions from indoor stoves and as of now, processed meat. However, the number of cases caused by each of these agents, or their cancer risk among the general population, varies. That’s because risk, from public health perspective, is a statistical property.
My grandpa ate 7 lbs of red meat every day and lived to be 130. Why didn’t he get cancer?
It’s impossible to determine if an individual will get cancer based on a lifestyle choice, whether it’s smoking or eating processed meat. Cancer occurs when a healthy cell acquires enough mutations to start replicating uncontrollably and the ability spread into new organs away from its site of origin.
Those mutations vary dramatically among the types of cancer (lung, pancreatic, colorectal, etc). They can even differ within a subtype, meaning a pancreatic cancer from one person can be genetically dissimilar than a pancreatic cancer in another human. Plus, a malignant tumor in a single individual is constantly evolving, and there is evidence suggesting no two cancer cells in the same tumor are the same. A cell’s ability to acquire these mutations depends on personal genetics, whether or not you inherited a predisposition from mom and dad, and exposure to compounds that are genotoxic; that is, can change your DNA.
How much processed meat is safe to eat?
On an individual level, it’s hard to say. On a population level, the WHO report cites an epidemiology meta analysis, which examined colorectal cancer studies going back to 1966. Based on that study, a person who eats 50 grams per day of processed meat has an 18 percent chance of developing colorectal cancer. A person who eats 100 grams has a 36 percent chance and so on. According to Cancer Research UK, 50 grams per day would be on par with two slices of ham.
For red meat, cancer risk elevates by 17 percent for every 100 grams per day that is consumed. When cancer risk levels of both processed meat and red meat were modeled together, the relationship maxed out at 140 grams per day.
Should you give up meat?
Not necessarily. Alice Bender, director of Nutrition Programs at American Institute for Cancer Research, said it’s important to remember the distinction that the WHO report makes between processed meat and red meat. “Processed meats even in small amounts were increasing risk, a little less than 2 ounces [which is equivalent to] a hot dog or few slices of cold cuts.” For red meat, what is important to keep in mind isn’t so much that you shouldn’t eat it at all, but more the amounts. It’s large amounts that become harmful.
There are benefits to red meat, and the findings don’t say that a balanced diet that includes red meat is bad. The report gives pause to the part of the diet that is high in meat consumption and red meat.