By Chris Radlicz

This past October, the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), made headlines when they classified processed meat as a Group 1 carcinogen. This classification was based on “sufficient evidence in humans that the consumption of processed meats causes colorectal cancer”. Additionally, red meat has been classified as a Group 2A carcinogen due to “limited evidence that consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect” [1]. These IARC statements advocating a limited intake of processed and red meats tend to be misconstrued by the public and many may take it to mean that all meat should be avoided. Besides the inherent benefits of protein and various micronutrients in meat, red meat is primarily trumpeted as the best source of heme-iron in the diet. With iron deficiency as the most common nutritional disorder in the world [2], limiting red meat may not be prudent advice. What, therefore, is unique to red meat and processed meats which explains their carcinogenic potential?

What gives meat a bad rap is not inherent in the animal muscle itself, but rather the preservatives added to meats and the cooking processes which meats undergo. So what can be done to mitigate and avoid the proposed cancerous effects of some meats? Below are some practical tips to be conscious of and implement when meat shopping and preparing meats so that consumers can take full advantage of the nourishment from meats while limiting any risk

• 1. Cook with Moist Heat: The Journal of the American Dietetic Association in a 2010 article, showed that cooking with dry heat promoted a 10 to 100-fold increase in advanced glycation end products (AGEs). AGEs increase oxidative stress and inflammation, and have shown to be a player in the pathogenesis of many chronic diseases. Cooking with moist heat, at low temperatures, and shorter cooking times have all been shown to reduce AGE formation [3]. Cooking meat in stews and sauces at low temperatures for longer periods of time, typical of crock-pot style cooking, is an effective way to reduce formation of these questionable AGEs.
• 2. Avoid Charring Meats: Cooking meat at high temperatures, typically on a grill or skillet, can lead to browning or charring. This browning is known to occur as a result of the Maillard reaction which has been shown to produce heterocyclic amines (HCAs), and polycyclic aromatic hydrocarbons (PAHs). PAHs form when fat from grilled meat is ignited, causing flames containing these PAHs, which can then adhere to the meat’s surface. HCAs are formed from amino acids, sugars, and creatine reacting at high temperatures. These chemicals have been shown to be mutagenic to DNA after consumption and digestion, leading to genetic instability and increased risk of cancer [4]. Cooking meats at higher temperatures and for long periods of time will lead to increased HCAs, while smoking and charring will result in more PAH formation. No Federal guidelines exist addressing PAH and HCA consumption, but these chemicals provide a mechanism as to meats carcinogenic capacity. With this in mind, the National Cancer Institute suggests that concerned individuals should turn meat over frequently when cooking, use a microwave first to shorten high temperature cooking time, remove charred portions of meat, and refrain from using gravy made from meat drippings as ways to reduce PAH and HCA exposure [5].
• 3. Purchase Nitrate-Free and Uncured Meats: Nitrates and nitrites added as preservatives to meat have been shown to convert to activated N-nitroso compounds (nitrosamines and nitrosamides) in the gut, and are proposed to be carcinogenic due to their ability to cause DNA damage [6]. N-nitroso compound formation can also be increased with the intake of red meat, principally due to interactions with the heme-iron [7].
• 4. Purchase Meat that isn’t Smoked: Smoked meats fall under the category of processed meats. Epidemiological studies, have shown a correlation between cancer of the intestinal tract and the frequency of dietary intake of smoked foods [8]. More convincingly, the smoking process forms N-nitroso compounds and inevitably contain high levels of PHAs.
• 5. Purchase Antibiotic-Free Meat– Some antibiotics and pesticides in meats can react with nitrite to form nitrosamines in high quantities [9]. Additionally, there is much worry that the antibiotic use in agriculture is contributing to the growing prevalence of antibiotic resistance, and in a more minor capacity, to the obesity epidemic [10,11]

Bibliography

[1]       WHO | Q&A on the carcinogenicity of the consumption of red meat and processed meat

[2]       Liu K, Kaffes AJ. Iron deficiency anaemia: a review of diagnosis, investigation and management. Eur J Gastroenterol Hepatol 2012;24:109–16. doi:10.1097/MEG.0b013e32834f3140.

[3]       Uribarri J, Woodruff S, Goodman S, Cai W, Chen X, Pyzik R, et al. Advanced glycation end products in foods and a practical guide to their reduction in the diet. J Am Diet Assoc 2010;110:911–6.e12. doi:10.1016/j.jada.2010.03.018.

[4]       Cross AJ, Sinha R. Meat-related mutagens/carcinogens in the etiology of colorectal cancer. Environ Mol Mutagen 2004;44:44–55. doi:10.1002/em.20030.

[5]       Knize MG, Felton JS. Formation and human risk of carcinogenic heterocyclic amines formed from natural precursors in meat. Nutr Rev 2005;63:158–65.

[6]       You C, Wang J, Dai X, Wang Y. Transcriptional inhibition and mutagenesis induced by N-nitroso compound-derived carboxymethylated thymidine adducts in DNA. Nucleic Acids Res 2015;43:1012–8. doi:10.1093/nar/gku1391.

[7]       Rohrmann S, Linseisen J. Processed meat: the real villain? Proc Nutr Soc 2015:1–9. doi:10.1017/S0029665115004255.

[8]       Fritz W, Soós K. Smoked food and cancer. Bibl Nutr Dieta 1980:57–64.

[9]       Elespuru RK, Lijinsky W. The formation of carcinogenic nitroso compounds from nitrite and some types of agricultural chemicals. Food Cosmet Toxicol 1973;11:807–17.

[10]     Cox LM, Blaser MJ. Antibiotics in early life and obesity. Nat Rev Endocrinol 2015;11:182–90. doi:10.1038/nrendo.2014.210.

[11]     Chang Q, Wang W, Regev-Yochay G, Lipsitch M, Hanage WP. Antibiotics in agriculture and the risk to human health: how worried should we be? Evol Appl 2015;8:240–7. doi:10.1111/eva.12185.