How to Choose the Right Food for your Pet

As a pet owner, what you choose to feed your dog or cat is probably one of the most important decisions you can make for his or her long term health—yet it's surprisingly complex. With hundreds of brands and varieties available, where do you even begin?
Choosing a diet for your pet is complex and will likely depend on several factors, such as the breed and age of your dog or cat, any health issues he or she may have, your budget, your personal preferences and possibly even your moral or ethical standards. As a veterinarian, I'm often asked which pet food is best; the truth is, no single food or diet is "best" for all pets. Just like the decisions we make regarding our own diets, there is a lot to consider when it comes to choosing a pet food. This article will cover the basics so you can make the best decision for you and your pet. Here are eight questions to ask when considering any new pet food.
What are my pet's unique needs?
Your pet's age, activity level and health status should all factor into the type of diet you choose. Does your dog or cat have any illnesses or documented food allergies or intolerances? If so, your pet might do best on a veterinary prescription food or one that eliminates a specific ingredient from his or her diet. Check with your veterinarian to help you determine the best diet for your pet if he or she has special needs. Just like people, not all dogs and cats will do well on the same diet. If your pet is gaining or losing weight despite feeding an appropriate amount, having gastrointestinal troubles, itching or losing hair, it may be necessary to evaluate his or her diet. Be sure to talk to your vet first to rule out any non-dietary issues.

What are the ingredients?
The first thing you should do when shopping for food for your dog or cat is check the ingredient list. Just like the food you buy at the grocery store, pet food packages feature various marketing lingo to draw us in. Pet food labels are complicated and can be tricky for the average consumer to decipher. However, since food companies are generally held to the same basic standards in terms of nutrient content (such as the specific amounts of protein, vitamins and minerals they contain), the major difference between brands is the quality of the ingredients.
Ingredients are listed on the back of the package in order by weight. Generally speaking, the first five ingredients are often the most important in terms of nutrient content, as they are present in the highest amounts and should be comprised of quality protein, grains, vegetables and fats. Be aware that ingredients toward the end of the list are probably only present in negligible amounts. For example, the front of a package may claim that a product is full of vegetables or antioxidants like blueberries, but if those ingredients are listed near or "lower" in the list than trace added vitamins or minerals, you know it's just hype—those ingredients are only in the product in negligible amounts that won't make a difference in your pet's health.
When it comes to key ingredients, here's what you need to know.
Choosing High-Quality Proteins
A good, high quality protein source should be among the first ingredients listed. Proteins are either listed as whole meat sources such as chicken, lamb, beef or salmon or as by-products (non-rendered parts of the animal other than meat, such as organs or fatty tissues) or by-product "meals," which are rendered (meaning all fat and water is removed) and ground. The specific type of protein you choose (chicken vs. beef vs. seafood vs. lamb) probably doesn't matter (whatever you and your pet prefers is fine) unless your dog or cat has a specific protein-related allergy. Soy (or soy flour) is another commonly used protein source in pet food. While many pets do fine on soy, it can cause some dogs and cats to produce more gas. For that reason, it is sometimes considered a less desirable protein source and is often present in higher amounts in cheaper pet foods, as soy protein costs less than animal protein.
The Deal with Meat By-Products
Some people have concerns about the use of by-products in pet foods. (A by-product generally refers to a portion of the animal not typically marketed for human consumption). Although the idea of feeding animal by-products to our pets may seem unappealing, from a nutritional standpoint it's probably not as offensive as it sounds (especially when we consider that our dogs' and cats' predecessors often consumed the entire bodies of their prey). In terms of protein and mineral content, whole meat and by-products are likely fairly equivalent. While it's ultimately up to the consumer to decide, it should be noted that by-products are simply the lesser used parts of the animal and do not contain things like hair, feathers or hooves that would be considered unfit for human consumption.
What about Grains?
Grains will typically be listed as either a whole grain source or a grain meal (ground grains). Brown rice, rolled oats and barley are all great choices and common ingredients in pet foods. There is a growing tendency among pet owners to want to avoid grains altogether—or specific types of grain such as wheat or corn—in their pets' food. This generally follows diet trends in humans. For example, gluten-free diets are a popular trend for us, so some people want to follow the same trend for their pets, assuming it might be better for them. However, aside from pets with specific allergies, most dogs and cats generally digest grains quite easily. Many grain-free diets contain higher sources of potato or other starchy carbohydrates to compensate for the lack of grain, which can actually lead to weight gain in some pets.
Finding the Right Fats
Quality fat sources commonly consist of beef or chicken fat, fish oil or flaxseed oil. If a fat comes from a single source, it can be named on the ingredients label as the source. Terms such as "animal fat" tend to be a little more ambiguous, and therefore may be less desirable to some consumers.
Other Ingredients
Vegetables such as sweet potatoes and peas will likely make up the remaining major ingredients in pet food. Generally speaking, the more reputable companies will typically use higher-quality ingredients in their products, so do your research when it comes to companies. You'll also see some general vitamins and minerals added near the end of the ingredients list, as well as some preservatives.  
Is the food AAFCO compliant and backed by research? Pet food is regulated by three different agencies: the United States Food and Drug Administration (FDA), the Association of American Feed Control Officials (AAFCO) and by each individual state. The basic goals are to make sure your pet's food is safe to eat, produced in a sanitary manner and labeled truthfully. AAFCO, in particular, was formed in an effort to establish consistent standards among all pet food companies. Because of AAFCO, a standard nutrition profile for dogs and cats was developed to ensure that all pet foods contain standard amounts of key nutrients (protein, fat, carbohydrates, vitamins, minerals) required to meet the basic function and needs of your pet. The system, while well-intentioned, unfortunately isn't foolproof. Regulation isn't as tight as it could be, rules aren't always enforced and errors can occur. Therefore, it's up to us as consumers to be proactive in educating ourselves on the best choices for our pets.   
Companies in compliance with AAFCO standards should be considered to produce foods that are complete and balanced for your pet, meaning they contain all of the necessary nutrients to support his or her basic functions. AAFO compliant companies should state so on the label. For optimal results, choose pet food from a company that can support its product with research based on actual food trials (meaning the diet has been fed for an extensive period to animals that have remained healthy).
Am I choosing this food for emotional reasons?
There's nothing wrong with gravitating toward a specific pet food company because their commercials make you smile, or because it's the brand your childhood pet always ate. However, don't let that warm and fuzzy feeling be the only driving force. Take time to research the company to make sure they have a good reputation, use quality ingredients and can back up their label claims.

Am I falling for meaningless labels or marketing ploys?
We all want the best for our pets, and for some people that means seeking specialty foods. However, there are no standard definitions for the terms "holistic," "organic" or "natural" when it comes to pet foods. These are typically marketing buzzwords that don't carry much weight or tell you anything about the quality of the product. Likewise, pet food companies that describe their product as "premium" or "gourmet" are not required to contain any higher-quality ingredients than other products. If you're truly interested in natural or organic ingredients, go straight to the ingredients list, which won't lie. Only the ingredients list will disclose exactly how natural or organic that food really is.
With the competitive nature of the pet food market, most companies do have marketing tricks up their sleeves. Just because a company utilizes flashy techniques to bait consumers doesn't necessarily mean that their product is higher or lower in quality. It does, however, require a little more diligence for consumers to evaluate claims with a critical eye.
Am I imposing my own diet preferences or beliefs onto my pet?
Grain-free, gluten-free, corn-free, vegetarian and vegan diets are all popular among people for various health and personal reasons. However, just because a diet is right for you, doesn't mean it's the best for your pet. It's important to lay your own dietary goals aside when it comes to feeding your pet and to do your research when it comes to the less mainstream diets.
In the case of pets with true food allergies, avoiding certain grains or proteins may indeed be warranted. (Your veterinarian or a veterinary dermatologist can help you determine the necessary steps to take if you suspect your pet may have a food allergy). Gluten intolerance, however, is not common among dogs and cats.
In terms of feeding dogs and cats a vegan or vegetarian diet, there really isn't sufficient research to show that these pets can subsist on an entirely plant-based diet. The fact of the matter remains that dogs and cats are natural meat eaters, and imposing our own moral and ethical beliefs onto them is probably neither fair nor appropriate. Feeding your pet in this manner without extensive research and/or supplementation can be damaging to his or her health, especially in the case of cats, who have more sensitive dietary needs and require specific amino acid profiles that cannot be obtained from a purely plant-based diet.
How much am I willing to spend?
Of course, there may be some exceptions to this rule, but generally speaking, you tend to get what you pay for when it comes to pet food. While it's true that the most expensive dog or cat food may not always be the best quality, the opposite, unfortunately, generally is true. Feed your pet the highest quality, well-balanced diet that is within your budget.

Where can I get more advice on my pet's diet?
Your veterinarian, who has a relationship with you and your pet, is probably the most valuable resource when it comes to making recommendations for your dog or cat. When in doubt, always check with your veterinarian first. Even if your vet is unable to answer your specific questions or concerns, he or she should always be willing to help and can at least point you in the right direction.
You can also refer to the source list below for more valuable information on pet food.
American Association of Feed Control Officials, "The Business of Pet Food: Labeling and Labeling Requirements,", accessed on October 17, 2013.
Nestle, Marion and Nesheim, Malden C. "Feed Your Pet Right." (New York: Free Press, 2010). 65-69, 90-95,99-103, 130-145.
U.S. Food and Drug Administration, "Pet Food,", accessed on October 17th, 2013.