Processed meat, such as bacon or hot dogs, causes cancer, a World Health Organization group said in a long-awaited determination on Monday. The group said red meat, including beef, pork and lamb, probably causes cancer, too.
Many studies show the links, both in populations of people and in tests that show how eating these foods can cause cancer, the International Agency for Research on Cancer (IARC) said in its report, released in the Lancet medical journal.
"These findings further support current public health recommendations to limit intake of meat," Dr. Christopher Wild, who directs IARC, said in a statement.
Most reports on the links between meat and cancer have been softened with some element of doubt, but the IARC uses clear and direct language in saying processed meat causes cancer. There are no phrases such as "may cause" in the report.
"Overall, the Working Group classified consumption of processed meat as 'carcinogenic to humans' on the basis of sufficient evidence for colorectal cancer," the report reads.
"Additionally, a positive association with the consumption of processed meat was found for stomach cancer. The Working Group classified consumption of red meat as 'probably carcinogenic to humans'," it added.
"Consumption of red meat was also positively associated with pancreatic and with prostate cancer."
It also defines red meat.
"Red meat refers to unprocessed mammalian muscle meat—for example, beef, veal, pork, lamb, mutton, horse, or goat meat—including minced or frozen meat; it is usually consumed cooked," the IARC said in its report.
"Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation. Most processed meats contain pork or beef, but might also contain other red meats, poultry, offal (eg, liver), or meat byproducts such as blood."
The report specifically names ham, hot dogs, sausages and jerky.
It's not startling news - the evidence has been building for years that eating meat, especially processed and red meat, raises the risk of cancer.
"The conclusion that processed meat (e.g., hot dogs, bacon, sausage, deli meats, etc.) causes cancer and that red meat (e.g., beef, pork, lamb) is a probable cause of cancer may come as a surprise to a public that for years has relied heavily on red and processed meats as a part of its diet," said Susan Gapstur of the American Cancer Society.
"In fact, classifying processed meat as carcinogenic and red meat as probably carcinogenic to humans is not unexpected. Indeed, based on earlier scientific studies, including findings from the American Cancer Society's Cancer Prevention Study II, the American Cancer Society has recommended limiting consumption of red and processed meat specifically since 2002," she added.
Official U.S. government dietary guidelines also recommend limiting meat. "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," they read.
The IARC assembled a team of experts to review all the evidence.
"The experts concluded that each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent," the IARC said.
"For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed," said IARC's Dr. Kurt Straif.
"In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance."
The U.S. National Cancer Institute says several more studies are ongoing to assess the risk. The American Institute for Cancer Research (AICR), which studies the role of lifestyle and cancer, said the report fits in with its own advice.
"For years AICR has been recommending that individuals reduce the amount of beef, pork, lamb and other red meats in their diets and avoid processed meats like bacon, sausage and hot dogs," AICR's Susan Higginbotham, a registered dietician, said in a statement.
"AICR's take-home message: by eating a healthy diet, staying a healthy weight and being active, AICR estimates that half of colorectal cancers could be prevented," the group added.
"In fact, for the most common U.S. cancers, healthy changes to Americans' diet, activity habits and weight could prevent an estimated one-third of cancers, about 340,000 cases a year."
Cancer is the No. 2 killer in the United States, after heart disease.