Nitrates are added as preservatives to processed meats. Nitrates can be readily reduced to form nitrites, which in turn can interact with dietary substrates such as amines and amides to produce N-nitroso compounds (NOCs): nitrosamines and nitrosamides, which are known mutagens and carcinogens. Nitrates or nitrites are used in smoked, salted, and pickled foods. Sodium and potassium nitrates are present in a variety of foods and give hot dogs and processed deli meats their pink color, but the main dietary sources are vegetables and drinking water.
Nitrates and nitrites are essential compounds, but they can become hazardous if they form nitrosamines. Nitrosamines can form if you cook nitrates or nitrites at high heat.
There are different types of nitrosamines, and many can increase the risk for cancer. Nitrosamines are some of the main carcinogens in tobacco smoke, for example Bacon, hot dogs, and processed meat can contain high levels of both sodium nitrite. They’re also high in protein, which is made up of amino acids. On exposure to high heat, this combination creates the perfect conditions for nitrosamines to form. Cooking vegetables, however, is less likely to produce nitrosamines. People rarely cook vegetables at very high heat, and they don’t contain large amounts of protein.
NOCs are also produced endogenously in the stomach and colon of people who eat large amounts of red meat. Studies looking at the detrimental effects of smoked foods have not demonstrated a clear, consistent connection between these foods and stomach cancer.
Diets with high amounts of fruits and vegetables that contain vitamin C and phytochemicals that can retard the conversion of nitrites to NOCs should be encouraged.
Charring or cooking meat at high temperatures over an open flame (400° F or more) can cause the formation of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs). PAHs have shown clear indications of mutagenicity and carcinogenicity.
Normal roasting or frying food does not produce large amounts of PAHs compared with the amount produced when cooking over open flames. Animal proteins that produce the greatest dripping of fat on to the flames register the highest PAH formation. For example, grilled beef produces larger amounts of PAHs than grilled chicken, which produces higher amounts than oven-grilled chicken. The source of the flame can also influence PAH production; charcoal grilling promotes the most, followed by flame gas, and finally oven grilling.
References:
World Cancer Research Fund (WCRF), American Institute for Cancer Research (AICR): Food, nutrition, physical activity, and the prevention of cancer: a global perspective, Washington, DC, 2007, AICR.
Kushi LH et al: American Cancer Society guidelines on nutrition and physical activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity, CA Cancer J Clin 62:30, 2012.
Farhadian A et al: Determination of polycyclic aromatic hydrocarbons in grilled meat, Food Control 21:606, 2010.
Edwards BK et al: Annual report to the nation on the status of cancer, 1975- 2010, featuring prevalence of comorbidity and impact on survival among persons with lung, colorectal, breast, or prostate cancer, Cancer 120:1290, 2014.
National Institutes of Health (NIH), National Cancer Institute (NCI): SEER Stat Fact Sheet: All Cancer Sites (website): http://seer.cancer.gov/statfacts/ html/all.html, 2014c. Accessed January 29, 2015.
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