Eating processed and red meats, including sausage and bacon, is linked to cancer in humans, the World Health Organization said Monday, but health experts cautioned that limiting or avoiding such foods is only “one piece of the lifestyle equation” that can reduce a person’s overall cancer risk.
Carolyn Lammersfeld, a registered dietitian and the vice president of integrative oncology at the Florida-based Cancer Treatment Centers of America, said there are many lifestyle factors that can reduce or increase the risk of developing cancer.
“We like to remind people that carrying extra body weight increases risk more than red meat or processed meat,” she said. “This is just sort of one piece in the lifestyle equation for reducing risk.”
Lammersfeld, however, said the WHO study was “vindicating” to many health professionals who have long warned of cancer risks from such meats. “It’s certainly aligned with what we tell our patients,” she said.
The WHO categorized processed meats in group 1. Items in that group are deemed carcinogenic to humans — the highest cancer-linked designation — such as the pesticide ingredient glyphosate and cigarettes.
Although processed meats are included with cigarettes, the WHO’s cancer arm, the International Agency for Research on Cancer (IARC), said that doesn’t mean they carry comparable risks.
“The classifications reflect the strength of the scientific evidence as to whether the agent causes cancer in humans but do not reflect how strong the effect is on the risk of developing cancer,” the IARC said in an emailed statement. “Comparisons within a category can be misleading … active smoking carries a much higher risk of lung cancer than does air pollution, although both are categorized in group 1.”
Processed and red meats can be carcinogenic to humans for several reasons, Lammersfeld said. Processed meats often have added preservatives called nitrates that can be converted into agents called nitrosamines, a known human carcinogen.
In red meats, heme iron, which gives the meat its red color, can be converted into nitrosamines. And when red meats are cooked at high temperatures, other carcinogenic compounds known as heterocyclic amines and polycyclic aromatic hydrocarbons can be formed, she said.
The WHO’s announcement said it is safe to eat up to 18 ounces of red meat a week, or the equivalent of less than two slices of bacon a day. The group emphasized that it is saying not that any amount of processed meat consumed will lead to the development of cancer but that its consumption should be limited.
“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,” Dr. Kurt Straif, the head of the IARC monographs program, said in the WHO news release. “In view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance.”
A person’s genetic predisposition to certain cancers can also affect how they should regard the warning.
“Certainly, if I were someone with a family history of colorectal cancer … I would definitely be heeding these warnings,” Lammersfeld said, adding that as personalized medicine advances, health care professionals will be able to give individuals more specific warnings on the basis of genetic factors.
Overall, Lammersfeld said, the WHO designation added to a wide body of evidence that is increasingly pointing to the carcinogenicity of processed and red meats.
The WHO said that the IARC working group looked at more than 800 studies investigating associations between dozens of cancers and the consumption of red or processed meats in many countries and populations with diverse diets before assigning the group 1 designation.
But whether that evidence and the WHO’s warning are converted into a warning label by the U.S. Food and Drug Administration remains to be seen.
“In the United States, the NIH [National Institutes of Health] national toxicology program carries out independent cancer hazard assessments. The [program] report on carcinogens has not specifically looked at red meats or processed meats as whole food items,” said Megan McSeveney of the FDA. “These substances have not been nominated for review for the next edition.”