This week, a study from Spain adds to the evidence that eating any type of meat (red, white processed, cured or organ meat) is associated with increased risk of colon cancer, and that cooking and processing meat increases risk (European Journal of Nutrition, Nov 24, 2016). Rare-cooked meats had a lower increased risk while grilled, griddled or barbecued meats had the highest risk.
That could explain why North Americans have a much higher cancer rate associated with meat-eating (Public Health Nutr, published online July 6, 2015) than Europeans and Asians do (Eur J Clin Nutr, 2013;67(6):598-606), because they grill their meat far more frequently. Another study found that pan-fried red meat was associated with increased colon cancer risk (Cancer Med, 2015;4(6):936-952). Pan-frying meat causes the highest levels of HeteroCyclic Amines (see below).
“Red” meat includes all meats from mammals: beef, veal, bison, pork, lamb, mutton, horse, deer, goat and so forth. Processed meats include all meat products that have been salted, cured, fermented, smoked, or preserved with other methods to extend shelf life and enhance flavor. Examples include hot dogs, ham, sausages, corned beef, beef jerky, bacon, and canned meats.
Last year, The World Health Organization’s International Agency for Research on Cancer has issued a report that eating processed meats raises risk for colon cancer, and that red meat may cause cancers of the colon, prostate or pancreas (The Lancet Oncology, 2015;16(6):1599-1600). Review of earlier studies showed that red meat is associated with increased risk for colon cancer (Am Coll Nutr, 2015;34(6):521-543), and that the more meat you eat, the greater your risk (Public Health Nutr, published online July 6, 2015].
How Cooking Method Can Affect Cancer Risk
The higher the temperature and the longer you cook meat, the more Advanced Glycation Endproducts (AGEs) are formed. When you cook food without water (grilling, oven broiling, pan frying or deep-fat frying), the sugar in the foods sticks to the protein and nucleic acids to form AGEs and HeteroCyclic Amines (HCAs). Polycyclic Aromatic Hydrocarbons (PAHs) are formed when fat drips from meat onto the heat source, causing flames and smoke that drive the PAH carcinogens back to the meat. PAHs, AGEs and HCAs are known carcinogens. On the other hand, when you cook food with water or water-based liquids, the sugars bind to water, which forms water and carbon dioxide which are harmless when they are blown off through the lungs.
Problems with Meat Processing
Curing or smoking meat causes formation of carcinogenic compounds called nitrosamines. Nitrosamines are also formed by the addition of nitrates, celery extract and other substances used to preserve the meats and make them palatable. Most lunch meats, hot dogs, ham, bacon, sausages, corned beef, beef jerky and canned meats contain nitrosamines. More than 30 years ago, manufacturers of lunch meats started to add anti-oxidants such as vitamin C, which can reduce, but does not completely prevent, the formation of nitrosamines.
• Most of you know that I do not eat meat and recommend that you avoid it also. However, data associating meat with colon cancer is on people who eat meat every day. I do not have any data showing increased risk for occasional meat eaters.
• You can meet your needs for protein without eating meat. Any combination of grains and beans contains all the essential amino acid building blocks for protein.
• If you choose to eat meat occasionally, restrict cooking directly in a flame, barbecuing and pan-frying. Water-based and lower-temperature cooking methods are preferable: stewing, cooking in a casserole or slow-cooker, stir-frying and so forth. Do not eat raw or under-cooked meats, which can cause infections.
• Adding antioxidant-rich spice mixes can reduce the formation of carcinogenic AGEs (Am J Clin Nutr, 2010;91(5):1180-1184).