Sodium nitrate is a relatively common food preservative that you'll find in a variety of products, particularly meats. However, while sodium nitrate helps prevent bacterial cultivation of meat products, it poses its own health risk in that it can turn into a cancer-promoting substance in the human body.
Sodium Nitrate
Sodium nitrate has the chemical composition NaNO3. It's also called saltpeter, and it's used in the production of fertilizer and explosives in addition to being an additive in preserved foods and packaged meats. Because sodium nitrate helps to inhibit bacterial growth, it extends the life of packaged meat products. You'll most commonly find sodium nitrate in heavily processed foods and salted meats such as hot dogs, sausage and bacon.
Nitrate, Nitrite and Nitrosamine
When you consume sodium nitrate, the sodium portion of the molecule separates from the nitrate portion. You can absorb sodium and as long as you don't consume it in excess, it doesn't hurt you. Your body can turn nitrate into nitrite, however, which has the formula NO2. Nitrites then react with secondary amines, which are present in large concentration in the proteins you eat, to form compounds called nitrosamines. Nitrosamines are carcinogenic, or cancer-causing, in humans.
Ascorbic Acid
Ascorbic acid, or vitamin C, helps to prevent nitrates and secondary amines from combining chemically to form nitrosamines, explains Dr. S. Tannenbaum and colleagues in a 1991 article in the "American Journal of Clinical Nutrition." Because of this, the United States requires that cured meats containing either nitrate or nitrite salts also contain ascorbic acid. However, while the presence of the vitamin C reduces the risk, it doesn't eliminate it.
Pregnancy
While everyone who consumes nitrates is at risk due to formation of nitrosamines, pregnant women should avoid nitrate-containing foods for an additional reason; the nitrites produced from ingested nitrates can cross the placenta. This can result in production of methemoglobin in a fetus, explains Dr. Nachman Gruener and colleagues in a 1973 article in the "Bulletin of Environmental Contamination and Toxicology." Methemoglobin isn't as efficient at delivering oxygen, so this can result in fetal oxygen deprivation.
References
- Linus Pauling Institute at Oregon State University: Nitrosamines and Cancer
- "American Journal of Clinical Nutrition"; Inhibition of Nitrosamine Formation By Ascorbic Acid; S. Tannenbaum, et al.; 1991
- "Bulletin of Environmental Contamination and Toxicology"; Methemoglobinemia Induced By Transplacental Passage of Nitrites in Rats; Nachman Gruener, et al; 1973
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