Sodium nitrite is chemical used to preserve meats and fish. It imparts a pink color to these animal proteins and prevents the growth of bacteria that cause botulism. Although it's more common in cat food, some manufacturers include sodium nitrite in canned dog food to preserve the freshness of ingredients.
Sodium nitrite is approved by the U.S. Food and Drug Administration for use as a preservative in canned pet foods that contain meat, fish or their byproducts. Foods must contain no more than 20 parts per million and packaging must list the amount of sodium nitrite included in the food. Sodium nitrite is considered harmful to dogs only in high doses. Amounts of sodium nitrite between 7.9 and 19.8 kg/mg per day can cause a blood disorder called methaemoglobin in dogs, according to an article in the March 2009 "European Food Safety Authority Journal." A lethal dose is considered 40 mg/kg.
Controversy and Considerations
When sodium nitrite combines with proteins, nitrosamines are formed. Nitrosamine ingestion can cause cancer in animals over time, the American Cancer Society says. Added preservatives like vitamin C in the form of ascorbic acid and vitamin E in an alpha-tocopherol may mitigate effects of sodium nitrite in dog foods, says Dr. Richard A. Scanlan of Oregon State University. If you're concerned, purchase sodium-nitrite-free canned and semi-moist dog foods.