Month: August 2020

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There are trends in pet food just like there are among humans. Increasingly, there has been a movement toward more “natural” pet foods. The idea is to feed pets a diet in line with what they would eat in the wild or what their ancestors ate. However, as my mother is fond of saying, arsenic is natural, too. We need to look past the marketing and make sure that these diets are really all they’re cracked up to be.

Grain-Free Diets

Grain-free diets are fairly self-explanatory. They contain no grains, i.e. wheat, corn, oats, rice, or any other crop in the group. These foods are also gluten-free, but not all gluten-free cat foods are grain-free, as gluten is a protein found in wheat, so other grains may still be included in some gluten-free diets. The concept behind grain-free cat food is that cats, as obligate carnivores, would not include grains in their native diet, which is mostly true. Cats would not chow down on grains in the wild, but they do eat their prey in its entirety, including the stomach contents, which can certainly include grains or other vegetation. The argument that a high-carbohydrate diet is unhealthy for cats still stands nonetheless, and this has largely been the appeal of grain-free cat food.

A Tufts University Study compared 35 grain-free dry cat diets to 42 regular dry cat diets and found that the average carbohydrate content of the grain-free diets was 12 g/1000 kcal lower (1). The individual carbohydrate contents varied widely, however, so it depends a lot upon the food in question (5). The carbohydrate levels are not all that matters, however. Cats are known to be able to digest grains and obtain nutrition from them (2, 3). Considering that cats evolved eating lots of rodents and rodents eat lots of grains, this makes sense.

Grain-free foods don’t simply ditch the carbohydrates–they replace the grains with starchy vegetables like potatoes, lentils, cassava, or peas. There isn’t much research on how digestible these plants are or how bioavailable their nutrients (3). At least some cats get gastrointestinal symptoms from consuming them (4, 5).

Some owners may choose grain-free diets over concerns about food allergies. But food allergies are uncommon in cats. A 2018 study found that only 0.1% of cats had them (10). When food allergies do develop, it is usually to animal products like beef or dairy, not plants (2, 3, 4). Gluten intolerance has not been documented in cats, so that’s no reason to avoid grains (3). Obviously, if your cat really does have a documented allergy to a grain, then you want to make sure their diet is at least free of that grain. If you suspect an allergy, talk to your veterinarian before you do anything else.

I would be remiss if I didn’t mention the concerns about grain-free diets and heart problems that have been brought up in the last several years. Although the connections are primarily being investigated in dogs, it has been impossible not to wonder if there is reason to be worried about cats. Around 2017-18, veterinarians began to raise concerns over cases they saw of dogs fed grain-free diets developing dilated cardiomyopathy, a form of heart disease causing an enlarged heart (6).

The US Food and Drug Administration (FDA) decided to investigate, and they still are. It’s thought that taurine deficiency might play a part, and diets containing legumes or potatoes as the primary carbohydrate might be the culprits, but it remains unclear (7). There were only a handful of reports on cats, so the FDA chose to focus on dogs, and there has been no further word on whether there may be a link between a grain-free diet and heart problems in cats (6).

Grain-free diets, at least the way they are manufactured today, are probably not as beneficial as we may have been led to believe. They may even be harmful, although more research will have to be done for us to know for sure. I’ll admit, I used to be one of those people who thought I had to feed my cats grain-free food. It sounds so much healthier for them! But that’s what marketing is for, isn’t it?

Limited Ingredient Diets

Limited ingredient diets, or L.I.D., are not just one thing. L.I.D. is a bit of an umbrella term, encompassing a group of diets that have a narrower range of ingredients than usual. They are generally meant for cats with known or suspected food allergies, and in fact they can be helpful for such cats. L.I.D. often contain only single protein and carbohydrate sources, i.e. lamb and rice or salmon and potato (8, 9). This makes is easy to be sure that a cat with food allergies or sensitivities is not eating an ingredient they are allergic to.

Many L.I.D. are made with “novel” sources of protein and/or carbohydrates that pets are unlikely to have encountered before, and therefore probably won’t have developed an allergy to (8, 9). These range from the rather mundane–duck, rabbit, sweet potato–to the very out in left field–alligator, kangaroo (8, 9). L.I.D. may also be used as part of a series of elimination diets to figure out what a cat with suspected food allergies is allergic to, under veterinary supervision (9).

Aside from cats with food allergies, some L.I.D.s may be helpful for cats with sensitive digestion as well (8). Otherwise, there is really no particular need for a healthy cat to be on a L.I.D. If you think your cat might benefit from one, especially if you suspect your cat may be suffering from allergies, talk to your veterinarian about it. Most cats with allergies are allergic to fleas or something else in their environment, not their food (10). If food allergies are suspected, there is a long process of testing via elimination diets to determine what, if anything, in the diet your cat is allergic to (9).

Raw Diets

This is a tough nut to crack. While I was doing my research, I read a particular article which was harshly critical of raw diets for cats. One of the drawbacks they listed was that there has been very little research done on these diets. As someone who was lately a research scientist, I kind of want to bash my head against a wall. The solution to a lack of research is to do the research, not to declare that the under-researched thing is bad.

But the fact that there is currently a lot of anecdotal information and not much in the way of scientific studies is a lot of the problem with raw diets, I think. It’s difficult to decide whether the proponents or the detractors have the firmer position because both have only a handful of studies to back them up. The rest is a matter of logic, tangential information, and beliefs.

Before we go any further down this rabbit hole, let’s talk about what a raw diet is. The definition can be a bit variable, but the basic principle is that the food is made of uncooked ingredients. A raw pet diet is mostly muscle meat, organs, ground bone, eggs, and sometimes vegetables, fruits, and dairy (11). Some people make homemade raw diets, but they can be purchased in a variety of forms as well. The goal is to simulate the natural diet of the pet, or its ancestors in the case of dogs, which are highly domesticated animals and don’t really have a natural diet. For cats, their diet in the wild, ideally, is whole prey animals like mice, birds, fish, and small reptiles.

Proponents of raw diets for cats say that raw meat is more nutritionally sound, having not been exposed to heat that might break down or alter nutrients, and it’s more biologically appropriate for cats anyway (12, 13). They claim that the diet can prevent or alleviate many feline ailments (13, 14). The evidence for this remains anecdotal, but this will necessarily be the case until rigorous research is done to investigate. Nonetheless, some veterinarians have begun to recommend raw diets based on their experience with them, but most fall into the other camp.

The detractors of raw diets, and there are many, say that raw diets are dangerous and have no major benefits. The American Veterinary Medical Association, American Animal Hospital Association, Companion Animal Parasite Council, and Centers for Disease Control have all taken a position against feeding pets raw diets (15). The primary concern is food-borne infections. This is the reason public health authorities tell us humans not to eat undercooked meat and to carefully avoid cross-contamination. Raw food, especially raw animal products, can carry bacteria and parasites. And studies have shown that raw pet foods do (12, 15), which is to be expected, really. The professionals who decry raw pet foods take the position that the risk of disease to both pets and humans outweighs what little benefit, if any, they see in these diets.

Even here there are two sides: those in favor point out that cats, being carnivores, have short, acidic digestive tracts designed for digesting meaty meals without allowing pathogens to proliferate in their guts (13, 14). Not to mention that cooked pet foods have been found to be contaminated with pathogens or toxins before, so perhaps to say raw foods are unsafe draws a false comparison (13)? That’s another case where I doubt anyone has crunched enough data to be sure. Even raw diet cheerleaders readily say that owners need to be careful not to give themselves food poisoning if they feed their cats a raw diet. Using proper food-handling technique should prevent any problems. It’s also important to dispose of uneaten food promptly and cleaning and sanitizing the food dish, as well as the area around it if any food gets on the floor.

Is raw food a good idea for your cat? In general, there’s so little concrete information that it’s hard to say. My instinct is that cats are carnivores, so it should be fine, as long as the diet is well-balanced. It needs to be either an approved commercial diet (AAFCO-approved in the United States) or a homemade diet using a recipe designed by a veterinarian or veterinary nutritionist. If you are thinking about going the homemade route, be very careful about looking for recipes on the internet, because there are lots of them, and many are just made up by people with cats, not experts in cat nutrition.

Also, some cats and some households should not use raw diets. Cats on immunosuppressants (like chemotherapy drugs) or high doses of steroids should not be feed raw food diets, as their immune systems may be more vulnerable to the pathogens in raw animal products (13). Households with very young children or elderly people, or anyone with a compromised immune system, probably shouldn’t use a raw cat food, either (11, 12, 13). Pathogens from their food can pass into a cat’s stool and even remain on the cat, especially on their face, in addition to the aforementioned concerns of pathogens being on food prep and feeding surfaces (12). In a home where there are people–or pets–with weak immune systems, this could be very dangerous. The jury may be out on raw diets in general, but there is definitely a subset of households where they will never be appropriate.

Works Cited

1. Prantil, L.R., Heinze, C.R., and Freeman, L.M. (2017). Comparison of carbohydrate content between grain-containing and grain-free dry cat diets and between reported and calculated carbohydrate values. Journal of Feline Medicine and Surgery, 20(4), 349-355. https://journals.sagepub.com/doi/full/10.1177/1098612X17710842
2. Freeman, L.M., Linder, D.E., and Heinze, C.R. (2016, June 14). Grain-free diets: Big on marketing, small on truth. Petfoodology. https://vetnutrition.tufts.edu/2016/06/grain-free-diets-big-on-marketing-small-on-truth/
3. Cats Only Vet Hospital. (2019, June 3). Grain free and other marketing trends. https://catsonlyvethosp.com/grain-free-other-marketing-trends/
4. Buzhardt, L. (n.d.) What’s in my cat’s food?: Designer diets, grain free diets. VCA Hospitals. https://vcahospitals.com/know-your-pet/whats-in-my-cats-food-designer-diets-grain-free-diets
5. Heinze, C.R. (2017, July 3). Research update: New insight into grain-free cat diets. Petfoodology. https://vetnutrition.tufts.edu/2017/07/research-update-new-insight-into-grain-free-cat-diets/
6. Cats Herd You. (2018, August 22). What do grain-free pet food warnings mean for cats? https://catsherdyou.com/what-do-grain-free-pet-food-warnings-mean-for-cats/
7. US Food and Drug Administration. (2018, July 12). FDA investigating potential connection between diet and cases of canine heart disease. https://www.fda.gov/animal-veterinary/cvm-updates/fda-investigating-potential-connection-between-diet-and-cases-canine-heart-disease
8. LID diets for dogs and cats. (2017, June 26). Pet Central, Chewy. https://petcentral.chewy.com/lid-diets-dogs-cats/
9. Anderson, K. (2020, July 2). Meals that heal: The best food for cats with allergies. The Dog People, Rover. https://www.rover.com/blog/best-food-cats-with-allergies/
10. Burns, K. (2018, June 27). Banfield: Few pets allergic to food; flea, environmental allergies rise. American Veterinary Medical Association. https://www.avma.org/javma-news/2018-07-15/banfield-few-pets-allergic-food-flea-environmental-allergies-rise
11. Association of American Feed Council Officials. (2012). Raw foods. https://talkspetfood.aafco.org/rawfoods
12. Stregowski, J. (2020, April 30). Should you feed your cat a raw diet? The Spruce Pets. https://www.thesprucepets.com/raw-food-diet-for-cats-552329
13. Tasi, A. (2020, January 6). Feeding raw: A veterinarian’s view. The Conscious Cat with Ingrid King. https://consciouscat.net/2020/01/06/feeding-raw-a-veterinarians-view/
14. Pierson, L.A. (2016, November). Feeding your cat: Knowing the basics of feline nutrition. Cat Info. https://catinfo.org/#Home-Prepared_Diets
15. Paul, M. (2014, September 24). The dangers of a raw diet for your cat. Pet Health Network. http://www.pethealthnetwork.com/cat-health/cat-diet-nutrition/dangers-a-raw-diet-your-cat

Published August 9th, 2020

Updated October 29th, 2020