People who eat a lot of red meat and processed meats have a higher risk of several types of cancer, including lung cancer and colorectal cancer, U.S. researchers reported.
The work is the first big study to show a link between meat and lung cancer. It also shows that people who eat a lot of meat have a higher risk of liver and esophageal cancer and that men raise their risk of pancreatic cancer by eating red meat.
"A decrease in the consumption of red and processed meat could reduce the incidence of cancer at multiple sites," Dr. Amanda Cross and colleagues at the U.S. National Cancer Institute wrote in their report, published in the Public Library of Science journal PLoS Medicine.
The researchers studied 500,000 people aged 50 to 71 who took part in a diet and health study done in conjunction with the AARP, formerly the American Association for Retired Persons.
After eight years, 53,396 cases of cancer were diagnosed.
"Statistically significant elevated risks (ranging from 20 percent to 60 percent) were evident for esophageal, colorectal, liver, and lung cancer, comparing individuals in the highest with those in the lowest quintile of red meat intake," the researchers wrote.
The people in the top 20 percent of eating processed meat had a 20 percent higher risk of colorectal cancer — mostly rectal cancer — and a 16 percent higher risk for lung cancer.
"Furthermore, red meat intake was associated with an elevated risk for cancers of the esophagus and liver," the researchers wrote.
These differences held even when smoking was accounted for.
"Red meat intake was not associated with gastric or bladder cancer, leukemia, lymphoma, or melanoma," added the researchers, whose study is freely available on the Internet.
Source of DNA mutations
Red meat was defined as all types of beef, pork and lamb. Processed meat included bacon, red meat sausage, poultry sausage, luncheon meats, cold cuts, ham and most types of hot dogs including turkey dogs.
Meats can cause cancer by several routes, the researchers noted. "For example, they are both sources of saturated fat and iron, which have independently been associated with carcinogenesis," the researchers wrote.
Meat is also a source of several chemicals known to cause DNA mutations, including N-nitroso compounds (NOCs), heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs).
Jeanine Genkinger of Georgetown University in Washington, D.C., and Anita Koushik of the University of Montreal said the findings fit in with other research.
"Meat consumption in relation to cancer risk has been reported in over a hundred epidemiological studies from many countries with diverse diets," they wrote in a commentary.