The World Cancer Research Fund International Continuous Update Project has released its recent findings from their review of about 400 studies. They found that the risk for colorectal cancer increases by 12 percent for every 100 grams per day of processed meat or red meat (Annals of Oncology, Aug 2017;28(8):1788-1802). A hot dog is about 50 grams.
In 2015, the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), reviewed 800 scientific studies and found that processed meat and red meat increased risk for cancers of the colon, prostate and pancreas (Lancet Oncology, Dec 2015;16(16):1599-1600). The report was written by 22 public health experts from 10 countries who concluded that the more meat a person eats, the more likely he or she is to develop cancer. Each 50 grams of processed meat (two slices of ham or a sausage) per day was associated with an 18 percent increased risk of colon cancer.
How Processed Meats May Cause Cancer
When meat is not sold fresh or frozen, it is often preserved by salting, curing, fermenting, smoking or adding chemical preservatives such as sodium nitrate. Common processed meats include hot dogs, ham, pastrami, corned beef, bacon, sausage, beef jerky, hot dogs, ham, salami, pepperoni and other packaged and delicatessen meats.
Nobody knows the specific factors in processed meat that cause them to be associated with increased risk for cancer, but some of the possibilities include:
• Nitrites, which occur naturally in all meats, but the quantities are increased in processed meats because additional nitrites are often used to prevent spoilage (Meat Sci, Jan 2008;78(1-2):68-76). Nitrites are converted in the meat and also in your body to nitrosamines that are known carcinogens (Carcinogenesis, Mar 2007;28(3):685-90). Cooking at high temperatures raises the nitrosamine content in all meats (Meat Sci, Jan 2008;78(1-2):68-76).
• Hemoglobin, which is full of iron to help carry oxygen through animals' bodies. Iron has been shown to damage cells and increase risk for genetic mutations that can become cancers.
• Fats, which increase bile production and insulin resistance, which both increase cancer risk.
• Cooking of processed meats such as bacon or hot dogs at high temperatures causes formation of heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Both are potent carcinogens (Nutr Cancer, 2013;65(8):1141-50), and the higher the temperature, the higher the levels of HCAs and PAHs (Toxicol Lett, 2007 Feb 5;168(3):219-27).
We have very good data to show that eating processed meats regularly is associated with increased risk of developing cancer, but we have no good data to show that eating these meats on occasion is harmful (although it may be). If you decide to eat these meats on occasion, you can help to protect yourself by:
• eating large amounts of fruits, vegetables, whole grains and nuts, all of which contain fiber and other anti-inflammatory agents that help to protect you from cancer (Br J Nutr, Jul 1, 2015;114(2):220-30)
• adding spices to your meats; virtually all spices and herbs are anti-inflammatory (J Food Sci, Aug 2008;73(6):T100-5)
• marinating meats before cooking and basting them with the marinade during cooking to lower surface temperature, which reduces the formation of HCAs and PAHs
• avoiding other known risk factors for cancers such as smoking, drinking alcohol, being overweight and not exercising.