Sodium nitrite is a food additive that is widely used in the meat industry as a color fixative and antibacterial agent to extend product shelf life and improve marketability. Sodium nitrite imparts a distinctive flavor to cured meats, such as hot dogs, bacon, ham, corned beef, bologna, meat spreads and some smoked fish products. When sodium nitrite interacts with proteins or other substances in your food, or when sodium nitrite-containing foods are cooked at high temperatures, carcinogenic nitrosamines are formed. These substances have been linked to cancers in the liver, lungs, pancreas and esophagus.
Dietary Link
According to a study published in the November 1993 issue of "Gastroenterology," Linxian, China -- now known as Linzhou -- has one of the highest rates of esophageal cancer in the world. A number of epidemiologic studies have been performed in this region to identify dietary or other factors contributing to the extraordinarily high incidence of cancer in this population. Although nutrient deficiencies and fungal infections have been implicated, a common finding in many of these investigations is the high consumption of nitrites and nitrates from local food and water sources.
Mechanism
The cells lining your gastrointestinal tract, including those in your esophagus, undergo frequent turnover and renewal. Cells that divide rapidly are more susceptible to genetic damage, which can trigger changes that initiate cancer. According to the 2010 issue of "Asian Pacific Journal of Cancer Prevention," sodium nitrite-derived nitrosamines are "unequivocal" genotoxins, and an April 2008 review in "Toxicological Sciences" reported that sodium nitrite interacts with a number of substances to form peroxynitrite, which can damage cellular DNA.
Evidence
In 2007, after a 30-year study involving more than 400 subjects, scientists in Sichuan, China, demonstrated a strong link between chronic occupational exposure to sodium nitrite and the development of esophageal cancer. Among 160 workers who were subjected to sodium nitrite exposure through skin, mouth and airway for an average of 22 years, 11 developed esophageal cancer and 10 developed various other malignancies. Among 255 workers from similar workshops where sodium nitrite exposure was strictly controlled, no cancers were found.
Considerations
Nitrosamines and other compounds derived from degradation of sodium nitrite are known carcinogens. The meat industry continues to add nitrites to its products to improve marketability because there is supposedly no effective substitute. While it is impossible to completely eliminate nitrites from your food -- they are a natural component of many vegetables and fresh meats -- limiting your consumption of processed, cured, smoked and overcooked meats will reduce your exposure to sodium nitrite.
References
- "Gastroenterology"; Squamous Dysplasia and Early Esophageal Cancer in the Linxian Region of China: Distinctive Endoscopic Lesions; S.M. Dawsey, et al.; November 1993
- "Proceedings of the National Academy of Sciences of the United States of America"; Enhancement of the Formation of the Esophageal Carcinogen Benzylmethylnitrosamine from its Precursors by Candida Albicans; C.C. Hsia, et al.; March 1981
- "Asian Pacific Journal of Cancer Prevention"; Carcinogenic Risk Assessment: Are There Dose Thresholds for Carcinogens?; S. Fukushima; 2010
- "Toxicological Sciences"; Combined Ascorbic Acid and Sodium Nitrite Treatment Induces Oxidative DNA Damage-Associated Mutagenicity in Vitro, but Lacks Initiation Activity in Rat Forestomach Epithelium; Y. Kuroiwa, et al.; April 2008
- "Diseases of the Esophagus"; Long-term Exposure to Sodium Nitrite and Risk of Esophageal Carcinoma: A Cohort Study for 30 Years; T.P. Xie, et al.; January 2011
- "Staying Healthy with Nutrition: Nitrites"; Elson M. Haas, M.D.; 2006
