Dietary Carbohydrates are NOT “Toxic” to Cats

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.

 

Refernces

  1. Carciofi AC, et al. J Anim Physiol Anim Nutr. 2008;92:326–336.
  2. De-Oliveira LD, et al. J Anim Sci. 2008;86:2237–2246.
  3. Fekete SG, et al. J Anim Physiol Anim Nutr. 2005;89:199–202.
  4. Morris JG, et al. Brit J Nutr. 1977;37:365–373.
  5. McCann TM, et al. J Feline Med Surg. 2007;9:289–299.
  6. Sallander M, et al. Acta Vet Scand. 2012;54:61
  7. Slingerland LI, et al. Vet J. 2009;179:247–253
  8. Verburgghe A., et al. Vet Sci. 2017;4(4):55.

 

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4 Responses to Dietary Carbohydrates are NOT “Toxic” to Cats

  1. Varonica says:

    It has been shown that a dry food only diet, thus carb heavy, Is detrimental to a cats health. In fact, many vets strongly recommend going to a wet food only diet..now. How did this change come about?
    I’m not a feed this way only pet owner. I believe variety is best, but I also try to limit as much as possible carbs in my cat’s diet. Obligated means must have, so cats must have meat protein without which they will sicken and die. Their systems are not designed to process carbs. We can feed carb heavy foods due to processing and supplements. Once upon a time, cats did die on kibble due to nutritional lacking. Science is a wonderful thing, but it is not always correct and “anecdotal” evidence is not always wrong. There are “screwups” on both sides.

  2. skeptvet says:

    Unfortunately, you have been misled. It has not been established that dry diets are harmful or that, if they are, the reason is the carbohydrate content. The entire point of this post and discussion is to raise awareness of the fact that these are unproven beliefs, not established facts, and that the existing evidence does not support such claims. Conclusions drawn from anecdotes can be true or false, but anecdotes themselves can’t prove them true or false since every claim is always supported by personal experiences, from the supposed dangers of dry cat food to the truth of astrology and the existence of aliens on Earth. You can always find stories for and against any claim, so stories themselves can’t prove claims true or false, which is what science is for.

  3. Miguel Morgado Santos says:

    The World Health Organization strongly advises people to avoid processed foods, namely due to their proven link with cancer (http://www.who.int/features/qa/cancer-red-meat/en/). However, most veterinarians promote processed foods as the best nutrition for pets. Why is it different?

    Before you use the excuse “humans and pets are different”, let me tell you that I am not just a pet owner spending all my free time reading pet blogs written by untrustworthy and biased authors. I am a researcher with a PhD in Evolutionary Biology, so heads up: I might be a little harder to trick! If processed foods should be avoided by people, then processed foods should be avoided by pets. If you disagree, please elaborate why is there less risk for pets in comparison to humans, with some NCBI references.

    Bottom line: if you were given two complete and balanced pet foods for the same price, but one was processed/dry and the other was freshly made, which one would you pick for your pet? (We both know the answer.)

    Best regards,
    Miguel Morgado Santos

  4. skeptvet says:

    The main problem with your reasoning is the concept of “processed.” Obviously, any food is “processed” if you don’t pick it out of the ground and eat it unwashed and uncooked. That’s obviously not a healthy choice. In human nutrition, “processed.” generally refers to convenience and snack foods, which are something entirely different in design and production than commercial pet foods. Here is a more detailed discussion copied from another of my articles:

    “Processed” pet foods
    I think it is also important to address the concept of “processed” food, since this term is egregiously misused in TAPC. Obviously, anything not eaten raw and unwashed is “processed” to some extent, the term is broad enough to be nearly meaningless. And despite the negative implications usually attached to the phrase, some kinds of processing clearly improve the safety and nutritional value of foods (washing and cooking, in particular). However, in TAPC, the term is used in an exclusively negative way, as a synonym for “unhealthy” and “toxic.”

    Most people probably hear the term and think of snacks and convenience foods for humans – potato chips, packaged hot dogs, frozen chicken nuggets, and so on. And there is some limited evidence that such foods may increase cancer risk in humans. Whether this is simply an association (e.g. people eating such foods are more likely to be overweight, exercise less, and have other risk factors for cancer), or a causal relationship (something in these foods increase cancer risk, directly or indirectly through something like increasing obesity) is unclear. In any case, clearly no one thinks a diet of convenience foods and snacks alone is healthy, and mainstream dietary guidelines recommend plenty of fresh fruits and vegetables, whole grains, low-fat protein sources, and so on because there is evidence to support the health benefits of such a diet. Therefore, it is reasonable to wonder how a packaged commercial diet could be safe or healthy for our pets.

    One key difference between human convenience foods and pet food is that the former are designed primarily to appeal to consumers. Taste, appearance, mouth feel, packaging, price, and most other characteristics of packaged foods for humans are aimed at getting people to buy them. Nutritional considerations are a negligible factor, apart from those that can be used as marketing tools (e.g. calling a cookie full of sugar “low-fat” or slapping a meaningless label like “no GMO” or “All Natural” on something to fool people into imagining it is healthier).

    Pet foods, in contrast, are typically designed by nutritional experts to be complete and balanced, and support normal health. Sure, they have to be appealing to pets in terms of taste and smell, and to owners (which includes being affordable and often leads to plenty of meaningless verbiage on packages). However, extensive research evidence exists demonstrating the nutritional needs of companion animals, and meeting these needs is a core requirement for a pet food from a reliable manufacturer. Pet foods are intended to be the primary source of nutrition, and they are formulated and manufactured with this in mind.

    Now most pet foods intended for adult maintenance or for growth in puppies and kittens have not been tested in large-scale, long-term clinical studies to demonstrate their impact on health. Some feeding trials are done for many diets, but these are foods, not medicines, so they are not required to meet that level of evidence. There are only a few commercial diets specifically intended for therapeutic medical uses, such as supporting animals with kidney disease, dissolving bladder stones, and so on. These have been through extensive pre-clinical and clinical trial testing to validate medical claims made for them.

    While it would be nice to have this kind of data for all commercial diets, it is false to suggest this means the health effects of feeding commercial foods haven’t been studied. And it certainly makes no sense to suggest that alternatives, such as raw or homemade diets, are healthier when there is even less evidence for the impact of those diets. The limited evidence so far suggests these alternatives are likely to be nutritionally incomplete or unbalanced (e.g. 1, 2, 3, 4) and have risks, such as exposing humans and pets to serious infectious diseases, that are not outweighed by any proven benefits (1, 2, 3).

    In theory, fresh, homemade diets that are properly formulated might be healthier than commercial pet foods. This is a reasonable hypothesis that can and should be investigated. However, the folks behind TAPC are basing their claims entirely on ideology, misuse of pre-clinical science, and ignoring the evidence and expertise of real veterinary nutrition experts, who are repeatedly dismissed using the shill gambit. The fearmongering in this series about “processed” foods and commercial pet diets is not founded on real evidence and is deeply misleading to pet owners trying to make decisions about how best to feed their animal companions.

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