“Preservative-Free” Pet Food? – Clinical Nutrition Service at Cummings School

Filtering out preservatives

When shopping in online retailers, there are often a variety of terms that can be used as filters to help consumers select pet food.  These include a few objective filters like food form (for example, dry or wet) or puppy/kitten (growing pets require a diet that meets their unique nutritional requirements).  However, most of the filters are based on marketing buzzwords like “no corn”, “grain-free”, “high protein”, “molasses-free”, and many more.  I’ve also come across many filters with even more vague and subjective criteria.  When I selected filters like “calming”, “appetite stimulation”, “immune support”, “scientific formula”, and “holistic”, the range of products that were shown made little sense.

Recently, I came across a company’s website with “preservative free” as one of the filters.  I was curious so selected this filter and was shown 165 dry options and 28 canned options for dog foods (interestingly, this “preservative-free” option was not available for cat foods).  It’s unclear why these 28 canned foods were designated as being “preservative-free” since canned food does not require a preservative so there wasn’t anything unique about these 28 foods compared to all of the other canned options (other than marketing).

For the 165 dry dog food options, the designation as “preservative-free” is more troubling since dry pet foods require preservatives to stay healthy and nutritious for our pets. To be clear, in many cases, it was the online store – not the manufacturer – that was designating the food as “preservative-free”.  In most cases, when manufacturers themselves make claims about preservatives in their dry foods, they carefully word their marketing to indicate that the food contains “no artificial preservatives”, not that they were preservative-free.  This is an important distinction because of the importance of preservatives in our pets’ dry foods.

Seeing this filter suggested to me that the term, “preservatives” is still a confusing one for some pet owners and one that is being used by companies for marketing purposes.  Therefore, I thought it would be helpful to provide some additional details on preservatives so owners can make more objective decisions about your pet’s food.

What are preservatives?

Preservatives are ingredients added to help ensure pet foods’ freshness and nutritional quality, which is critical so that it is safe and nutritious for our pets.  Preservatives often have a bad reputation but it’s important to be aware that there are different types of preservatives.  There are synthetic (lab-produced) preservatives, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), or ethoxyquin, as well as natural preservatives, such as vitamin E (also known as tocopherol), vitamin C (also known as ascorbic acid), or rosemary extract.

Preservatives – whether synthetic or natural – are an absolute must for dry dog and cat foods.  The airtight storage that results from the canning process protects canned pet food so preservatives are not required for this form of pet food.  Dog and cat foods are typically quite high in fat and fat is the ingredient in food most susceptible to spoilage (oxidation).  Spoiled fat not only makes the food less tasty, but it can also decrease the nutritional quality of food (certain vitamins need fat to remain stable) or even make the food unsafe to eat.  Preservatives prevent spoilage of the fat and help to maintain the food’s taste, nutritional quality, and safety.

Despite a lack of evidence for health problems tied to artificial preservatives, consumer demand has driven pet food manufacturers to switch over to using natural preservatives in nearly all products.

When I first started out as a veterinary nutritionist, most dry pet foods used synthetic preservatives.  Over the years, synthetic preservatives have been blamed for everything from arthritis to kidney disease to cancer, although no proof of such health effects has ever been scientifically documented.  Despite a lack of evidence for health problems tied to artificial preservatives, consumer demand has driven pet food manufacturers to switch over to using natural preservatives in nearly all products.  In fact, it’s now difficult to find pet foods that do contain artificial preservatives!  Today’s dry pet foods use natural preservatives in the fat sources, added to the entire diet, or both.  If a pet food’s ingredient list states something like “…chicken fat (preserved with mixed tocopherols)…”, you’ll know that the food’s main fat source was preserved with vitamin E.  However, these foods might include additional vitamin E or vitamin C on the ingredient list and it’s impossible to know whether these ingredients are added for their nutritional effects, as a preservative, or both (although the bodies of dogs and cats make their own vitamin C so they don’t need it in the diet for nutritional reasons).

One disadvantage of natural preservatives is that they are not as potent as the synthetic ones, so the duration of their protection isn’t as long in pet foods.  Manufacturers should account for this in their “best by” date on the package, but natural preservatives make it even more important that you store your pet food properly.

When you see a dry pet food being marketed as “preservative-free”, look closely.  Most of the time, the manufacturer has carefully worded their marketing to indicate that the food is free of artificial preservatives.  I have seen occasional dry pet foods that are not as careful and don’t make that distinction and state that they are “preservative-free”.  In most cases, these foods do contain natural preservatives on the ingredient list so they’re probably safe (but this less than careful marketing should raise a red flag).  If a dry food is truly preservative-free, I would be concerned about its safety and nutritional quality!  If the marketing for a canned food says it’s “preservative-free”, it probably is – just like almost all other canned foods – so, while accurate, it’s taking advantage of pet owners.  Now that you know more about preservatives and why they’re so important, you can judge preservative-related marketing efforts more objectively!

Lisa M. Freeman, DVM, PhD, DACVIM (Nutrition)

Dr. Freeman is a veterinary nutritionist and a professor at Cummings School of Veterinary Medicine at Tufts University. She is on the cutting-edge of science, with hundreds of articles in prestigious journals, speaking engagements at national and international conferences, and awards for her scientific achievements. However, she also is passionate about providing objective and accurate information on pet nutrition to veterinarians, pet owners, and other animal enthusiasts.