Bacon, sausage and other processed meats are now ranked alongside cigarettes and asbestos as known carcinogens, the World Health Organization announced today. Processed meats cause cancer, and red meat likely causes cancer, the health agency says in a new report.
The new investigation involved 22 scientists who were invited by the WHO’s International Agency for Research on Cancer to assess the association between more than 16 types of cancer and the consumption of red meat and processed meat.
Over the course of seven days in early October, the scientific panel examined more than 800 epidemiological studies from the U.S., Europe, Japan, Australia and elsewhere. The scope covered multiple ethnicities and global diets, according to the report which was published today in the journal Lancet Oncology.
The WHO group “classified consumption of processed meat as ‘carcinogenic to humans’ on the basis of sufficient evidence for colorectal cancer.” Colorectal cancer is the second most lethal form of cancer in the U.S., causing nearly 50,000 deaths per year. Processed meat was also linked to a higher incidence of stomach cancer.
Red meat carries a slightly lower risk, the group says, but is still “probably carcinogenic to humans.” Aside from the “strong mechanistic evidence” related to colorectal cancer, the “consumption of red meat was also positively associated with pancreatic and with prostate cancer.
As a main line of evidence, the group cites one study from 2011, which combed through 28 studies on meat consumption and cancer risk dating back to 1966. That meta analysis found that colorectal cancer risk jumps by 17 percent for every 100 grams (3.5 ounces) of red meat consumed each day. Meanwhile with processed meat, colorectal cancer risk increases by 18 percent for every 50 grams (1.7 ounces) eaten each day.
The International Agency for Research on Cancer keeps a list of compounds or activities with suspected, probable and definitive links to cancer, with each possible item falling into a designated grouping based on whether or not it causes cancer.
Processed meat now falls into “group 1,” meaning it ranks as high as tobacco smoking, the most dangerous variants of human papillomavirus (HPV) and asbestos exposure in terms of causing cancer. Red meat lands in “group 2A” with inorganic lead.
Research in rodents and human tissue shows meat consumption increases the production of chemical compounds, including haem iron and its chemical byproduct N-nitroso-compounds (NOCs). NOCs cause oxidative damage to intestinal tissue that is carcinogenic. Curing meats elevates the levels of NOCs as well as carcinogenic compounds called polycyclic aromatic hydrocarbons. Heating meat leads to the formation of heterocyclic aromatic amines, a known mutagen and cancer-causing agent.
“High-temperature cooking by pan-frying, grilling, or barbecuing generally produces the highest amounts of these chemicals,” the report states.
The new analysis makes a definitive assertion on the connection between eating meat and cancer. In recent years, studies and health policy groups have linked the two activities, but often without explicitly saying meat causes cancer. Take, for example, the American Cancer Society’s position as of this morning:
Because of a wealth of studies linking colon cancer to diets high in red meats (beef, lamb, or liver) and processed meats (hot dogs, bologna, etc.), the Society encourages people to eat more vegetables and fish and less red and processed meats.
As the Guardian reported, the WHO’s new position aligns the views with other health agencies like the World Cancer Research Fund, which has said there is convincing evidence that processed meats cause bowel cancer.
Though a majority of the WHO’s panel agreed to these assessments, the final decision was not unanimous.
The beef industry has been preparing a rebuttal for months to meet the WHO’s announcement, according to The Washington Post:
“We simply don’t think the evidence support 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, told The Washington Post.