Folks who are critical of commercial pet foods or advocates for raw diets and other alternatives often rail against the evils of carbohydrates. The idea that dietary carbs cause disease is a central thesis of the recent “Truth About Pet Cancer” video series (my response to which is coming soon!). With cats in particular, the claim is made that since they are obligate carnivores, carbohydrates are effectively poison for this species, causing diabetes, cancer and all sorts of other diseases. There’s only one small problem with this claim: it isn’t true!
What is true is that cats are obligate carnivores, meaning that they only eat animal prey in the wild. However, the idea that this means animal prey is all they can eat is a fallacy. Cats do have biological adaptations to eating prey, which means they have no requirement for carbohydrates in the diet, and they require more protein, and somewhat different amino acids in the diet than dogs and humans. However, this is a far cry from the wild claims made about carbohydrates causing disease.
At the recent American College of Veterinary Internal Medicine (ACVIM) forum, there was a great evidence-based presentation reviewing this subject:
Laflamme D. Cats and Carbohydrates: Why is this Still Controversial. ACVIM Forum, Seattle, WA. June, 2018.
Dr. Laflamme begins by referring to a 2010 ACVIM consensus statement which I reported on many years ago. Though no complete consensus was reached, the bottom line was that the most important dietary risk factor for cats, and the most common nutrition-related disorders (diabetes and obesity) are due primarily to excessive calorie intake, NOT dietary carbohydrate content.
Research has shown that cats can digest and utilize carbohydrates nearly as well as dogs, so they are an appropriate source of calories.1-4 Carbophobes often behave as if all carbohydrates are the same, and that any carbohydrate is equivalent to eating pure sugar. That is, of course, nonsense. While too much refined simple sugar in the diet can have negative effects on both humans and cats, complex carbohydrates and fiber do not, and can actually have positive effects. Dr. Laflamme points out that while it is possible to raise blood sugar in cats with extreme dietary manipulations (fasting them then feeding a single meal very high in carbs and low in protein), the normal type of carbohydrates used in cat foods fed in a normal manner has no apparent effect on glucose or insulin levels, so there is no reason to believe these diets would increase the risk of diabetes.
In a more real-world type of study, there have been three reports looking at what actual pet cats are fed and whether this influences the risk of diabetes. One of these found a greater chance of diabetes in cats fed only dry or only canned compared with a combination of the two.5 This makes little sense physiologically, and the study did not consider changes in diet that often go along with the diagnosis and treatment of diabetes, so this result is questionable. Two other similar studies which did look specifically at the diet fed before the onset of diabetes found no association between dry diets and diabetes.6-7 It is also worth noting that the vast majority of cats in the U.S. and Australia eat at least half dry food, and almost half of cats eat only dry. If dry food causes diabetes, a lot of cats should have this disease, yet this disease only occurs in between 0.2% and 0.75% of cats.
Another important health concern often blamed on carbs is obesity. Contrary to the claim that dietary carbohydrates cause obesity in cats, there is evidence that diets relatively higher in carbs than in fat actually reduce the risk of this problem. Cats naturally limit their own carbohydrate intake, and carbs are less caloric than fat, so cats on higher carb diets tend to eat fewer calories and so are less likely to be obese. Some of the low-carb dets marketed to reduce obesity and diabetes risk based on the idea that carbs are “bad” for cats actually raise the risk of obesity because they are high-fat and very caloric!8
Of course, anything can be harmful in excess, even water and oxygen. Extremely high carbohydrate diets, above about 50% of calories, can cause diarrhea and potentially raise blood sugar levels in cats. Such diets also make it difficult to ensure adequate protein intake. However, the existing evidence suggests that in appropriate forms and amounts, there is no reason to believe dietary carbohydrates are harmful to cats, and they even have some potential benefits. The fear-mongering about carbs and commercial diets promoted by advocates of raw food and alternative medicine simply isn’t consistent with the facts.
- Carciofi AC, et al. J Anim Physiol Anim Nutr. 2008;92:326–336.
- De-Oliveira LD, et al. J Anim Sci. 2008;86:2237–2246.
- Fekete SG, et al. J Anim Physiol Anim Nutr. 2005;89:199–202.
- Morris JG, et al. Brit J Nutr. 1977;37:365–373.
- McCann TM, et al. J Feline Med Surg. 2007;9:289–299.
- Sallander M, et al. Acta Vet Scand. 2012;54:61
- Slingerland LI, et al. Vet J. 2009;179:247–253
- Verburgghe A., et al. Vet Sci. 2017;4(4):55.