Without preservatives the shelf life and safety of most processed foods would be limited if not impossible. Preservatives inhibit bacterial and fungal growth such as molds. They prevent spoilage, stabilize nutrients and maintain flavor. Antioxidant preservatives protect from the oxidation of fat and prevent rancidity. Preservatives serve the same function in dog food. But health concerns about synthetic preservatives worry many dog owners. Owners are demanding more “natural” preservatives unaware of the unintended consequences.
Ethoxyquin, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroquinone (TBHQ) and propylene glycol have commonly been used in dog food. These preservatives have the advantages of being inexpensive, very stable during the extreme heats of dog food processing, and required in very small amounts.
Ethoxyquin, BHA, BHT and TBHQ have various concerns of cancer risks in humans. Although the evidence is not direct many manufacturers have voluntarily discontinued the use of some and substantially reduced the quantities of others in food. None have been shown to be a cancer risk in dogs, especially at the levels presently used. However, objections to their use are widely voiced.
Guilt by association is a major objection. These compounds are used in other industries like the rubber, cosmetic, petroleum and packaging industries. Because those industries are so different than food, the implication is that they are the same as the products they preserve (rubber, petroleum, jet fuel). That is like saying that because we use salt to de-ice roads salt is like asphalt and should not be used in food.
Propylene glycol has been found to cause a particular type of anemia in cats and has been removed from cat food. It does not have the same affect in dogs and is still used in dog food. Propylene glycol is chemically related to ethylene glycol, the active ingredient in anti-freeze. Anti-freeze is toxic to dogs. Because of their chemical similarity, critics are fond of saying that the use of propylene glycol is adding toxic anti-freeze to dog food. It is not toxic to dogs and is not the same as its cousin in anti-freeze.
Mixed tocopherols (various forms of vitamin E), ascorbic acid (vitamin C), rosemary extract, marigold extract and citric acid are natural antioxidants and preservatives. Their use in dog food has increased since the growing concerns about synthetic preservatives. These natural preservatives are much more expensive than synthetic ones. They are also extremely heat sensitive so they must be used in large quantities to ensure sufficient levels in the dog food after processing. This substantially increases the cost of dog foods. This unintended consequence prices some dog owners out of many dog food brands.
The easiest way to avoid all of controversy and problems with preservatives is to switch from commercial dog food altogether. Homemade dog food does not need preservatives. Refrigeration and freezing preserve the nutrients and flavors without chemical additives.
~Dr Ken Tudor
THE DOG DIETITIAN