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Are popular dog foods and ingredients like corn healthy or just fillers?

Updated on September 23rd, 2025

Pet's info: Dog | Cavalier King Charles Spaniel | Female | spayed | 6 years and 3 months old | 17 lbs

Are grocery store foods and foods like purina and royal canin/science diet considered McDonald's for dogs? (Junk food) why or why not? Please explain. Also why are ingredients like corn, meat byproducts, wheat, soy, etc. considered healthy? These seem like filler ingredients to me. Aren't sweet potatoes, brown rice, peas and named meat meals healthier and more nutritious? What is the science behind corn and wheat etc. being nutritious or actually good and wholesome for dogs? Can someone explain?

2 Answers

Most Helpful Answer

Answered By David Elbeze, DVM, MRCVS

Veterinarian

Published on October 9th, 2018

These brands you mentioned are considered at least in my mind to be mid range foods, it's no McDonald's but it's not super healthy either. same foes for all the ingredients you mentioned, these are indeed fillers, some more problematic than others (such as meat byproducts for example). Dogs are considered omnivores but are truly carnivores, meaning they need mainly meat/fish in their diet, but economically and realistically it's not doable, there are too many dogs/cats and not enough meat on earth to keep with the demand.

2Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Jessica Desrosiers
Veterinary Technician
Published on October 10th, 2018
That's a lot of questions! I'm not the person you originally asked this to, but perhaps I can help.

Foods like Royal Canin and Science Diet are actually considered OK quality foods, and not really "junk food". Junk food type diets tend to be almost all filler, or have poor quality ingredients such as low grade protein sources, cellulose fillers, etc.

Meat byproducts, corn, wheat, etc aren't considered low-quality fillers depending on how they are processed. Items like whole corn are going to be hard to digest, obviously, (think about when you eat corn on the cob versus say, a corn muffin, and the end result) but corn once ground down actually provides a great carbohydrate energy source as the insides of the kernel are very easily digestible. The same goes with other grains such as wheat. Meat byproducts still provide a great source of proteins, calcium, etc that provide nutrition provided they are broken down into more easily digestible components before being added into the food.

Food items like peas, rice, sweet potato, etc, can definitely provide great nutrition as well, and may be easier to digest if your pet has an underlying condition that either causes an allergy to ingredients such as wheat or corn, or other underlying health issue where protein/vitamin levels, etc may need to be altered to treat the issue. These can also be good alternative sources for pets with sensitive stomachs or skin issues, again due to allergies to other ingredients.

The end case boils down to your pet's individual needs, if they have any healthy issues, and if they have any food allergies. If you find your dog does just great on Science Diet, then sticking with that diet is perfectly fine. If you feel they do better on something with rice or sweet potato, then offering those foods instead works out well too.
2Pet Parents found this answer helpful

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Are grains and byproducts in dog food just fillers? Is Hill's premium?

Basically, there is proponent of people in the media and in the "natural" food sector that would like to make everyone believe that grains are the devil and that dogs are wolves. This is, in fact, incorrect. Wheat and soy, grains, contain valuable nutrients including proteins that dogs can readily digest and utilize appropriately. While it is true that there are dogs that get GI upset from consumption of these, the same can be said about beef, chicken, and any other meat protein. Rice, oats, and potatoes are acceptable in small quantities, but do contain starches which are complex sugars, and are a little more difficult to digest. In terms of by-products, this is usually referring to any part of the animal that is not the flesh of the beast. Usually this includes certain organs, bones, blood, etc. These products can be ground up and made into a byproduct - meal of sorts. Obviously, the actual meat is going to contain more appropriate nutrients but if a dog were left to it, they would be happy to eat any and all pieces of an animal. As for specific brands of food, Hill's is the brand that I typically recommend to all my clients and which I feed to my own dogs and cats. I consider it to be very high quality. I can't speak much about the other brand you've named unfortunately as I have little knowledge about it. Hope this helped though!

Updated on September 23rd, 2025

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Why are corn, wheat, soy, byproducts in dog food considered bad?

Again, there is no known problem with these ingredients. The stigma about byproducts is especially annoying, because byproducts like liver, kidney and other organs have great nutritional value compared with meat. The reason behind the stigma is not easy to understand. It really has to do with a series of non- professionals speculating on unsupported theories and then spreading the information as if it's truth. The same happens with people...just look at all the fad diets that come and go. While there may be some shred of evidence that these ingredients may have potential to cause harm, there is not nearly enough for a professional to say that they are bad and other ingredients are good. You can see that the pet food industry has responded to the unsupported claims of grains, natural ingredients, byproducts and even raw food, but please don't take that as confirmation that these ingredients are bad or good. It's nothing more than sales strategy and responding to consumer demands. This is a huge topic that I cannot begin to cover here, so I'll give you a couple links to some helpful articles: https://www.petcoach.co/article/what-to-look-for-when-choosing-your-pet-s-food https://www2.vet.cornell.edu/news/20130205/what-pet-food-should-i-feed

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Are sweet potato, potato, and rice healthy carbs in dog food?

The word "filler" is not exactly accurate and has been perpetuated by a great deal of false information spread about dog food lately. The truth is that these ingredients actually have a great deal of nutrients and properties that make them an important part of the diet. Dogs are actually omnivores (similar to humans) and are not meant to eat an all meat diet, so it's expected that some degree of carbohydrates are in the diet and all the packaged dog foods are formulated to meet the known nutritional demand of dogs. Additionally, carbohydrates such as rice and potatoes are good for promoting a healthy digestive system. For these reasons, all the mentioned ingredients are good ingredients to have in dog food. The benefit of brown vs white rice is not well known and any claims that one is better than the other are usually not well supported by the facts. Same goes for different types of potatoes. The easiest way to sift through the vast amount of information about dog food is to always check the source of the information. If the information is coming from a veterinary nutritionist, then it can be trusted. Veterinarians are also good sources of information, but be wary if the veterinarian is speaking on behalf of a certain company. If the source of the information is coming from someone without these qualifications, then it's best to be very skeptical. I hope that helps.

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Is corn and wheat in Royal Canin dog food safe or just filler?

Thank you for submitting your question regarding diets. Royal Canin is great pet food company as they have veterinarians on staff to formulate and research their diets. This is not something small niche brand companies can afford to do. Very few dogs actually have allergies to wheat. It is typically a breed problem with Irish Setters. As far as corn, it is actually a high quality ingredient despite the bad press. It provides a complete protein source and many essential fatty acids. There is so much misinformation from other pet food companies trying to make their diets unique. Additionally, very fre dogs have allergies to corn. Thank you for the exc question. I hope this information helps!

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Are rice, oats, barley in dog food fillers or beneficial for dogs?

I am going to give an answer that is likely different than what you are expecting and is somewhat vague. There is a great deal of marketing and misinformation out there that speaks in terms of absolutes, but unfortunately the answer is much more complex than and can't be stated as good or bad. The term filler has not and is not commonly used appropriately. All of the ingredients you listed are good sources of nutrition and are appropriate for dog food, because dogs are omnivores (similar to people). Filler implies the ingredient has little or no nutritional value, but these ingredients do contribute vital nutrients such as vitamins, minerals, and essential fatty acids to pet foods. These products also provide protein, which may be easier for the pet to digest than some proteins from meat. Most dogs and cats (>90%) can utilize and digest nutrients from grains normally found in pet foods. One other thing to keep in mind is that these ingredients are one of a few different ingredients that are scientifically formulated in order to meet the known nutritional demands of your dog. These ingredients are utilized for the nutrients they are high in, so depending on the food, one may be more appropriate to use than the other. Given this, I cannot say that one is better than the other. For more information about dog food, I recommend you read the articles at the links below. https://www.petcoach.co/article/what-to-look-for-when-choosing-your-pet-s-food/ https://www.fda.gov/AnimalVeterinary/ResourcesforYou/ucm047113.htm I hope that helps and all is well with Chloe.

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Why is pet food so confusing? Are corn, raw, and brands really good?

Hello! All great questions and comments - and you're right, there's a lot of conflicting information out there regarding food. Some of the information you're going to find is based on personal preference or a value bias. Corn is a good source of digestible carbs, fatty acids, and protein - but these things are better digested in dogs than in cats (who are obligate carnivores), and some people prefer to minimize grains, so those people might state corn is "bad".... in my opinion, the focus on grains is based more on trends in human nutrition than evidence-based pet nutrition. Statements regarding what pet foods are "good" vs "bad" will also come from personal preference...your vet can probably explain what made them state that Purina is better than Merrick, and another vet might have their own input on the matter. I do personally like both Purina and Hills because I find their products consistent, reliable, and I like that those companies put a lot of their profits back into nutrition research to work on creating good foods - but that doesn't mean they're the only good foods out there. Raw food is another hot topic. I have worked extensively with dog mushers, and raw meat is a very common component to their food - and I'm fine with that. However, I also have a degree in Public Health, and know that raw foods increase the likelihood of foodborne illness such as salmonella both in the pets themselves, and in the humans who are in contact with them. So, again, there are going to be different sides to the conversation. It's confusing when there's conflicting information! Try to sort through what's based on research and evidence, and what is based on the personal opinions and biases of the speaker. Good luck! Hope this helps.

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Is corn a poor quality ingredient in dog food? What about digestion?

No, corn is not a poor quality ingredient, it is a good source of carbohydrate. Corn is also rich in vitamin C, magnesium, B vitamins and carotenoids, contains very little fat, and is a good source of fiber.

Updated on September 23rd, 2025

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