Tag: diet

Science

Hyperthyroidism

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Thyroid disease is fairly common in cats, especially as they get on in years. The most frequent type of thyroid disease in older cats is hyperthyroidism [1, 4]. My parents’ elderly cat, Rosie, has it. So did my roommate’s cat Coco. And so do my best friend’s two ancient gray ladies. Even though hyperthyroidism is a common illness, I will attest that it can still be mystifying at times. It can impact a cat’s entire body, and it isn’t completely understood even by scientists and veterinarians. It is diagnosable and treatable, however. Sometimes, hyperthyroidism can even be cured.

Graphic of cat thyroid gland
The thyroid gland – Image from Cornell Feline Health Center

What is Hyperthyroidism?

The thyroid gland is a small organ found in all vertebrates which produces the thyroxine (T4) and triiodothyronine (T3) hormones. In mammals, the thyroid is found in the throat and has two lobes. Thyroid hormones regulate a wide variety of bodily functions. When the thyroid produces too much T3 and T4, it’s called hyperthyroidism. Hyperthyroidism increases the body’s metabolism which can cause problems with many different organs and systems.

Cats typically develop hyperthyroidism when middle-aged or older [1, 2, 7, 8, 10]. Up to 10% of cats age 10 and older may have hyperthyroidism [1, 3, 8]. It’s uncommon in cats younger than that, however [1, 2, 7, 8]. Untreated hyperthyroidism is fatal, but today the prognosis for a cat with this disease is usually optimistic.

How is Hyperthyroidism Diagnosed?

If your veterinarian suspects hyperthyroidism, they will probably do a physical examination of your cat’s neck to see if they can feel that the thyroid is enlarged [1, 2, 4, 7]. The presence or absence of a suspicious lump isn’t enough for a diagnosis, however. Most of the time, the final diagnosis can be made with a total thyroxine, or TT4, blood serum test [10]. The vast majority of hyperthyroid cats will have very high T4 levels with a TT4 test, making the diagnosis clear right away [1, 2, 7, 10].

However, cats with hypothyroidism occasionally have T4 serum levels that fall within normal limits [1, 2, 7, 10]. T4 levels fluctuate, so your veterinarian may decide to try the test again in a few weeks [1, 7]. Or they might try other thyroid hormone blood tests. A thyroid scan is another option but must be performed at a specialty veterinary facility [7, 10].

What are the Symptoms?

Because thyroid hormones affect so many parts of the body, the symptoms of hyperthyroidism are varied and sometimes nonspecific. They include:

Graphic of cat with hyperthyroidism
Characteristic appearance of hyperthyroid cat – Image from Cornell Feline Health Center
  • Weight loss/muscle wasting
  • Increased appetite
  • Increased thirst and urination
  • Vomiting
  • Diarrhea
  • Hyperactivity
  • Unkempt fur
  • Aggression or irritability
  • Fast heartrate
  • Increased vocalization, especially at night
  • Weakness
  • Heat intolerance

Some cats demonstrate “apathetic hyperthyroidism,” where they are lethargic, anorexic, and depressed/dull instead of the more usual symptoms [1]. Hyperthyroidism is progressive, so symptoms may be very mild at first [2]. It’s also not uncommon for hyperthyroid cats to also have other diseases, especially since they tend to be older. Many of these symptoms can be symptoms of something else. The safest bet is to consult your veterinarian anytime your cat seems different or unwell.

Secondary Illnesses

An overactive thyroid can sometimes cause other organs to become diseased. The heart is particularly at risk. There is a form of heart disease known as thyrotoxic cardiomyopathy which is caused by the heart muscle working overtime to meet the demands of a metabolism on overdrive [10]. The heart muscle thickens as a result of pumping so hard, but then that makes it difficult for the heart to work properly [2, 4, 10]. This can lead to heart failure. Fortunately, successful treatment of the hyperthyroidism can improve and even reverse the cardiomyopathy [2, 7, 10].

Hyperthyroid cats frequently experience high blood pressure as a cardiac complication, too [2, 4, 10]. About 25% of the time, in fact [10]. In severe cases, the high blood pressure can damage their organs [2, 4, 10]. It can even lead to retinal detachment that renders them permanently blind [4, 10]. High blood pressure is no joke and needs to be managed alongside hyperthyroidism until the thyroid hormones are under control [2]. If the hyperthyroidism is resolved, the blood pressure usually takes care of itself [2, 10].

What Causes Hyperthyroidism?

Hyperthyroidism usually begins when the thyroid gland becomes enlarged [2, 10]. In cats, this is almost always the result of a benign tumor called an adenoma [2, 4]. In less than 2% of cases, the growth is cancerous [1, 10]. What causes the abnormal thyroid tissue growth to begin with, however, remains uncertain. Researchers have found evidence for both environmental and biological factors that may play a role.

Environment

There is a demonstrated association between diet and the chances of a cat developing hyperthyroidism. Too much iodine in the diet may make a cat susceptible [10]. Canned cat food is also associated with higher rates of hyperthyroidism [1, 5]. The results of a 1999 study suggest cats fed primarily canned food have a rate of hyperthyroidism 2 to 3 times higher than other cats [5]. Researchers still don’t know why canned food would lead to an overactive thyroid. Correlation is not causation, so there may be more going on here that we don’t understand yet.

Using cat litter has also been found to be a potential risk factor, with the same study showing triple the rate of hyperthyroidism in cats that use litter [5]. Again, although there is a potential link, there is as yet no explanation. From looking through a lot of research papers to write this article, I know that veterinary scientists are still hard at work trying to figure out feline hyperthyroidism. The disease just doesn’t want to give up its secrets easily.

Certain household chemicals are associated with higher rates of feline hyperthyroidism, too. Polybrominated diphenyl esters (PBDE), which are used as flame retardants, have been found in high levels in the blood serum of hyperthyroid cats [1]. According to the Environmental Protection Agency factsheet for PBDE, rodent studies have shown thyroid toxicity from PBDE exposure. Per- and polyfluoroalkyl substances (PFAS) are a versatile group of artificial chemicals with a wide variety of applications in industry and the home. Wang et al. found that PFAS levels, particularly perfluorooctanoic acid, were higher in hyperthyroid cats than the cats in the control group [9]. The Environmental Protection Agency lists tumor growth and thyroid hormone disruption among the effects of PFAS in animals.

Siamese cat in meadow
Siamese have a reduced rate of hyperthyroidism – Image by rihaij from Pixabay

Biology

Hyperthyroid cats may have defects in the way their cells communicate that lead to the adenomas and other tissue abnormalities that overproduce thyroid hormones. Cats with thyroid nodules sometimes have low levels of the G protein in their thyroids [1]. A lack of G protein can decrease the inhibition of cell growth [1]. Some cats with thyroid nodules or adenomas have a cancer-causing mutation, known as an oncogene, which could cause the excessive cell growth [1].

Certain breeds of cat are less likely to develop the disease: Siamese, Burmese, Tonkinese, Himalayan, Persian, Abyssinian, and British Shorthair [3, 5, 9, 10]. At one time, only the Siamese, Burmese, and Persian/Himalayan were known to have these decreased risk, so the benefit was thought to be associated with the color-point pattern or lighter coat colors [3]. This hypothesis ultimately didn’t hold up [3], but perhaps there is something special these breeds have in common which will one day come to light. The same study which discovered the three new resistant breeds also found that long-haired, nonpedigree cats have higher rates of hyperthyroidism [3]. This despite the extremely long-haired Persian and Himalayan’s decreased rate.

What Treatments are Available?

Radioactive Iodine

It might sound a little scary, but radioactive iodine is actually the gold standard for treating feline hyperthyroidism. This treatment can only be done in specialized veterinary clinics that are authorized to work with radioactive materials, so it may not be accessible or affordable for everyone [2, 7, 10]. It’s a great option if you can take it, though, because for about 95% of cats it cures their hyperthyroidism–even those few with cancerous thyroid tumors [1, 2].

Radioactive iodine therapy relies on the fact that the thyroid takes up iodine to synthesize thyroid hormones. The cat is injected with the radioactive version of iodine, I-131 [1, 2, 7, 10]. No anesthesia is required [2, 7, 10]. The cat’s thyroid absorbs the I-131, just like it would normal iodine, but the abnormal thyroid tissue that’s churning out T3 and T4 like crazy is hogging the iodine. So the radioactive molecules get sucked into the abnormal tissue and kill it, leaving alone the cat’s healthy tissues, including any healthy thyroid tissue [1, 2, 7, 10].

Although the procedure is quite safe for the cat, it can be dangerous for the people around the cat which is now shedding radioactive particles [2]. Cats have to be hospitalized for a week or two after radioactive iodine therapy so that their radiation levels can get low enough for release [1, 2, 7, 10]. Even then, special care has to be taken at home for a two weeks after [1].

Radioactive iodine therapy may be a good option for cats that cannot undergo anesthesia. It also works well for cats with ectopic thyroid [7]. Ectopic thyroid is thyroid tissue somewhere other than the usual location of the thyroid gland such as under the tongue or in the chest [10]. It can be in locations that would be difficult to remove surgically. Radioactive iodine therapy doesn’t usually have complications, but for the rare cat it works too well and they become hypothyroid instead [2]. The solution to this is medication with thyroid hormones.

Medication

Hyperthyroidism cannot be cured with medication, but it can be managed with it. The medicine is called methimazole [1, 4, 7, 10]. Its brand names are Felimazole and Tapazole [4, 7, 10]. Methimazole is available as an oral tablet or a gel applied to the skin [1, 2]. It works by decreasing the production and release of hormones from the thyroid [2, 4]. It’s usually given twice a day [1, 4].

Cats may be given methimazole as a long-term method of managing their disease or to stabilize them before trying a more permanent solution [1, 4, 7]. Like all drugs, methimazole can have side effects. According to the Food and Drug Administration, the most common side effects of methimazole in cats are changes in appetite, lethargy, vomiting, diarrhea, skin lesions, itchiness, unusual vocalizations, weight loss, fur abnormalities, weakness, and agitation [4]. However, a small percentage of cats develop severe side effects with methimazole [1, 4]. Namely, liver disease, anemia, low blood platelets, and low white blood cell counts [1, 4, 7, 10]. Always report medication side effects, even seemingly small ones, to your veterinarian.

Two veterinarians holding white cat
Photo by Gustavo Fring from Pexels

Surgery

When Dr. Jean Holzworth first recognized feline hyperthyroidism in 1978, the only way to treat it was to remove the offending thyroid gland [1]. Although there are now other options, for some cats this is still the chosen course of treatment. For most cats, surgery cures their hyperthyroidism [2]. It can also be done at a regular veterinary surgery rather than the special facility required for radioactive iodine therapy, making it accessible to more people. Surgery requires a cat to go under anesthesia, however, and for older cats who often have other health problems, that can be a risky proposition [2, 10].

Surgery also carries a chance of complications. Complications aren’t likely, but they do happen. Most cats still have enough thyroid cells left after the surgery to keep up their T3 and T4 hormone levels, but some become hypothyroid and require medication [7]. Another possible complication is damage to the parathyroid glands, which are near or within the thyroid are necessary for maintaining normal calcium levels in the blood [2, 7]. If the parathyroid glands become damaged, the cat may develop low blood calcium and require supplemental calcium or vitamin D [1, 7]. Other complications include damage to nearby nerves or the larynx [1, 7].

Due to the risks associated with surgery and the availability of alternatives, it isn’t a very common choice anymore [2]. That being said, it might still be the right option for you and your cat. That’s something you would have to figure out with your veterinarian.

Diet

The research is still ongoing for diet as a means of controlling hyperthyroidism in cats [2]. For cats with health concerns that make other treatment options difficult or impossible, however, it can be the best–or only–choice despite being somewhat controversial. The principle is that limiting the amount of iodine in the cat’s diet to a small, controlled amount restricts the amount of hormones the thyroid can make. Cats fed a prescription iodine-restricted diet and nothing else should return to normal thyroid function [1, 7, 10]. Nothing else really means NOTHING else. No treats, don’t even put the prescription food in a bowl that has been used for other food or untreated water [1, 10]. The iodine-restricted diet contains only 0.2 parts per million of iodine [10]. That is a really, really small amount. It would not take much to throw off the balance.

In memory of Coco and Rosenberg

Works Cited

  1. Brewer, W. G., Jr. (2020, July 6). Treating feline hyperthyroidism. Blue Pearl. https://bluepearlvet.com/medical-library-for-dvms/treating-feline-hyperthyroidism/
  2. Cornell Feline Health Center. (2017, January). Hyperthyroidism in cats. Cornell University Collège of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hyperthyroidism-cats
  3. Crossley, V. J., Debnath, A., Chang, Y. M., Fowkes, R. C., et al. (2017). Breed, coat color, and hair length as risk factors for hyperthyroidism in cats. Journal of Veterinary Internal Medicine, 31(4), 1028-1034. https://doi.org/10.1111/jvim.14737
  4. Food and Drug Administration. (2019, December 3). Hyperthyroidism in cats: There’s an FDA-approved drug to treat it. FDA.gov. https://www.fda.gov/animal-veterinary/animal-health-literacy/hyperthyroidism-cats-theres-fda-approved-drug-treat-it
  5. Kass, P. H., Peterson, M. E., Levy, J., James, K., et al. (1999). Evaluation of environmental, nutritional, and host factors in cats with hyperthyroidism. Journal of Veterinary Internal Medicine, 13(4), 323-329. https://doi.org/10.1111/j.1939-1676.1999.tb02189.x
  6. Peterson, M. E., Castellano, C. A., and Rishniw, M. (2016). Evaluation of body weight, body condition, and muscle condition in cats with hyperthyroidism. Journal of Veterinary Internal Medicine, 30(6), 1780-1789. https://doi.org/10.1111/jvim.14591
  7. Pet Health Topics. (n.d.). Hyperthyroidism in cats. Washington State University College of Veterinary Medicine. https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/diseases/hyperthyroidism-in-cats
  8. Stephens, M. J., O’Neill, D. G., Church, D. B., McGreevy, P. D., et al. (2014). Feline hyperthyroidism reported in primary-care veterinary practices in England: Prevalence, associated factors and spatial distribution. Veterinary Record, 175(18), 458. https://doi.org/10.1136/vr.102431
  9. Wang, M., Guo, W., Gardner, S., Petreas, M., et al. (2018). Per- and polyfluoroalkyl substances in Northern California cats: Temporal comparison and a possible link to cat hyperthyroidism. Environmental Toxicology and Chemistry, 37(10), 2523-2529. https://doi.org/10.1002/etc.4239
  10. Williams, K., Downing, R., and Ward, E. (n.d.). Hyperthyroidism in cats. VCA Hospitals. https://vcahospitals.com/know-your-pet/hyperthyroidism-in-cats

Published April 25th, 2021

Updated June 14th, 2023

Cat Care

In Search of the Best Cat Food, Part V: Do Indoor Cats Need Indoor Food?

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

At last, we have come to the final installment of our series on cat food. There remain many questions, I admit, but I am only one person, and there are so, so many kinds of cat food. So I have tried to cover the basics to the best of my ability, and I hope you have learned as much as I have. Today we bring this journey to a close with a question that has haunted me for a long time. Is indoor cat food better for indoor cats?

Image by Crepessuzette from Pixabay

I had always assumed it must be. Why would they make food just for indoor cats (and dogs) if they’re nutritional needs weren’t somehow different? When I became a proper adult and had to buy food for my own kitten, I realized it was actually kind of difficult to find indoor kitten food, and I started to wonder if it might just be a marketing gimmick. But a couple years prior, when I’d bought my hedgehog, I was told I should feed her either hedgehog food or indoor cat food, and indoor cat food only. I was receiving conflicting signals, and I never really got a clear answer. Now the confusion shall end.

The simple answer to the question of whether indoor cats need indoor food is: it depends on the cat. Isn’t that so often the case? The lives of indoor and outdoor cats differ in many ways, but individual cats can be at least as different from each other in either environment, so you have to get to know your cat and possibly ask your veterinarian whether an indoor diet is appropriate, and I’ll explain why momentarily. First, let’s look at what exactly an indoor cat food is.

The formulations vary by company, as is to be expected, but the one thing all indoor diets have in common is a lower calorie content than other cat food. Indoor cats simply do not have the space to roam that outdoor or semi-outdoor cats do, so indoor cats are generally less active and may become overweight. Most indoor diets are also high in fiber. This contributes to the lower calorie count and helps prevent hairballs (1). Indoor cats spend more time grooming than outdoor cats. They may also shed more, being in an environment of consistent light and temperature that confuses their normal shedding cycles (1). Therefore, more hairballs.

Cats tend to be a lot more acrobatic outdoors – Image by rihaij from Pixabay

Some indoor diets may also claim to improve stool quality and/or smell (1, 2). Hill’s Science Diet lists immune-supporting antioxidants and high levels of the fat-burning amino acid carnitine as features of their indoor diet, in addition to low calories and high fiber (3). It is generally agreed that the basic nutritional requirements of indoor and outdoor cats are no different (1, 4). That being said, some indoor cats certainly do have problems with gaining too much weight or coughing up too many hairballs. These cats may benefit from an indoor diet. Changes in weight and lots of hairballs can both be indicative of medical problems, so be sure to check with your veterinarian that there isn’t something more serious going on.

There are some drawbacks to an indoor diet, of course. In in order to decrease calories and increase fiber, the protein content may have to be sacrificed (4). Make sure to carefully examine the protein content so that you know if your cat will be getting enough. Because of the way pet food labels are written, you may have to do some math. See part one of this series for a cat’s protein requirements. Some cats may also benefit more from a diet that is low calorie only or hairball-preventative only. As in, why restrict calories any more than you have to if your cat just needs help with their hairballs? Moreover, many “light” or “low-calorie” cat foods are essentially the same as an indoor diet (1), so keep that in mind when trying to decide what the best option for an overweight kitty is.

To bring things full circle, some indoor cats are likely to benefit from an indoor diet. My first cats, Milo and Cara, absolutely did. Both were very lazy kitties, and it was a struggle to keep their weight under control for much of their lives. Milo was a shorthair, but he shed like crazy, and Cara had long, luscious hair. Both had hairballs, especially Cara. They were fed indoor food most of their lives to help those problems. While Milo was still a pretty fat cat, it did seem to make a difference. I fed Joon an indoor diet for a while because I thought I had to, but I have since stopped. There is nothing inactive about that cat, and her short, fine hair has never given her a hairball in her life. Each cat is different.

Indoor cats can be couch potatoes – Image by photosforyou from Pixabay

I suppose that’s really what this series comes down to. Each cat is different, and each owner has to make the best decisions they can for their cat or cats. There are some things that are true for all cats. They are obligate carnivores. There are certain key nutrients that have to be included in their diets which omnivorous animals like us don’t need. They need to get enough water from their food to be sufficiently hydrated. But every kitty is an individual, and their needs change throughout their life, too. Just like us. The approach to pet food has been pretty one-size-fits-all for a long time. The baffling variety of options today hopefully reflects a shift toward a more flexible, individual approach. It’s our responsibility as pet parents to make sure we look past the marketing to find the best cat food we can for our furry friends.

Post Script: In case anyone was wondering, I still don’t know why hedgehogs must have indoor cat food. If you would like to enlighten me, I am all ears.

Works Cited

  1. Loria, K. (2018, January 22). What’s the difference between indoor cat food and regular cat food? Pet Central, Chewy. https://petcentral.chewy.com/whats-the-difference-between-indoor-cat-food-and-regular-cat-food/
  2. Purina. (n.d.). Feeding your indoor cat. https://www.purina.co.uk/cats/health-and-nutrition/daily-feeding-guide/feeding-your-indoor-cat
  3. Hill’s Pet. (2019, October 30). Nutritional needs of an indoor cat. https://www.hillspet.com/cat-care/nutrition-feeding/best-cat-food-for-indoor-cats-nutritional-needs
  4. Nielsen, M. (2020, May 15). Indoor cat food vs regular food: Why and what to choose. Feline Living. https://www.felineliving.net/indoor-cat-food-vs-regular/#
  5. Country Veterinary Clinic. (n.d.). Best food for indoor cats. Country Veterinary Clinic Blog. https://www.countryvet.net/post/best-food-for-indoor-cats.html

Published August 23rd, 2020

Updated October 15th, 2020

Cat Care

In Search of the Best Cat Food, Part IV: Grain-Free, L.I.D., & Raw Diets

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

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

Photo by Nick Fewings on Unsplash

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.

Novel source of protein? – Image by sven kopping from Pixabay

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.

Image by A_Different_Perspective from Pixabay

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

Cat Care

In Search of the Best Cat Food, Part III: Kitten, Adult, & Senior Diets

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Meredith Hemphill

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Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

The pet food industry offers diets for every stage of a cat’s life, from formula for newborn kittens to senior cat food. The kitten milk-replacement is one thing, but what’s the difference between solid food for kittens, adults, and seniors? And what about the cat food that says it’s for “all life stages”? Today we look at the difference between diets for the various life stages and what really matters for your cat.

Cat and two kittens eating from bowls
Image by mariahuusgaard from Pixabay

Kitten Food

Before doing this research, I knew there was at least one difference between kitten food and any other cat food. I took Joon in when she was about four months old, and I was living with a roommate that already had a cat. Domino is a gorgeous tuxedo cat with spooky yellow eyes, and she was quite pudgy. My roommate had to put her on a diet, and Domino was not a fan. She kept eating Joon’s food, which Joon was too busy playing to care about. My vet told me I should be careful to keep her from doing this, because kitten food is high in calories.

It makes sense, doesn’t it? Kittens are still growing rapidly, and as they get older they use up a lot of energy playing as well. In fact, kittens may need up to three times as many calories as an adult cat each day (1, 2, 3)! And they have higher protein requirements than adults, as well, needing to get about 30% of all that energy from protein (2). Most of the rest of the calories need to come from fat to ensure that they get enough essential fatty acids for proper development (1). Kittens need lots of vitamins and minerals as well. Basically, like all babies, kittens need lots of nutrients in their diet so they can grow up big and strong. So kitten food is made more nutrient-dense than adult food.

The Association of American Feed Control Officials (AAFCO) requires kitten food to be at least 30% protein and 9% fat on a dry matter basis (4). A survey of 212 adult and kitten foods by IdleCat found that kitten foods actually averaged 40.77% protein for kibble and 49.11% protein for canned food (3). The fat content was a little closer to the minimum recommendation, but for both kinds of food was more than 21% higher than the average fat content of the adult foods (3). Carbohydrate and fiber content were lower to compensate (3). Vitamins and minerals weren’t measured in that survey, but in a well-balanced kitten food they should be present in higher amounts as well.

Kitten food is also made to be easier for small mouths with developing teeth to eat. Canned kitten diets are typically softer, and the kibble comes in smaller pieces (1). However, the nutritional differences are what is most likely to impact a cat’s health. Adult cat food is usually not nutrient-dense enough for kittens, although it will do temporarily in a pinch (5). Conversely, as my vet told me, kitten food can cause adult cats to gain too much weight. Depending on the nutrients included, the extra vitamins and minerals could even cause toxicity in an adult cat (1). A few bites here or there is unlikely to cause anybody any harm–Domino is certainly none the worse for it–but kittens need kitten food and adults should be kept away from it as best we can.

Cats are considered kittens up to one year of age, with the exception of some large breeds. Maine Coons do not reach maturity for up to two years. If you are unsure how long to keep feeding your cat a kitten diet, check with your veterinarian.

Tortoiseshell cat eating from bowl
Image by sweetlouise from Pixabay

Adult Cat Food

Adult cat foods are formulated to maintain a grown cat’s weight and health. Growth and development never completely stop. All organisms continue to make new cells, repair damaged tissues, and progress through their life cycle as long as they live. However, an adult cat uses much less energy than a kitten to do these things, so they need far fewer calories and other nutrients relative to their body weight. This is reflected in the nutritive content of adult cat food.

The AAFCO divides their standards for cat food into two categories: “growth and reproduction,” for kittens and pregnant or lactating queens, and “adult maintenance” for the average, older, and sterilized adult cat (6). The minimum protein content for adult maintenance is 4% lower than the recommendation for kittens and queens. The fat minimum is the same, but 5 out of 12 mineral recommendations are lower for adults, as well as Vitamin A (4). These minerals and vitamin can cause toxicity in excess, which is more likely in adult cats who use less of the nutrients than a growing kitten or a queen who is growing kittens.

Cats are typically considered “adults” from the age of one year to seven years, although this varies some by breed and individual cat (7). Those of us with rescue cats often don’t know exactly how old they are, so you and your vet may have to play it by ear to decide when the time seems right to start treating your cat like a senior.

Senior Cat Food

In the United States, the AAFCO is the government body responsible for licensing pet food, and as previously indicated, they don’t issue standards for senior cat food. The consequence of this is that senior cat food is very similar to adult cat food, with some slight modifications that won’t color outside the AAFCO adult cat food guidelines (8). Whether this is a bad thing or not is hard to say. A lot remains unknown about the needs of senior cats. Due to lack of research, many of the decisions made about how to feed senior pets have been made based on what is known about aging humans (9). Even so, there have been improvements in senior cat diets over the years.

But some cats may not need to go on a senior diet at all, or not until much later in life. If an older cat is keeping up their body weight and muscle condition on their adult diet, there’s no need to change them to a senior diet (8). If a senior kitty begins to gain or lose weight or lose muscle mass and no associated health problem is found, a change in diet may be in order (8). However, senior cat diets can be pretty different from one another. Of course, cats with age-related health problems may be put on a diet specific to their needs. If your vet recommends just plain senior cat food, however, the variability in formulations can be overwhelming.

Fat tortoiseshell cat
Cats sometimes gain weight as they get older – Image by Quinn Kampschroer from Pixabay

It used to be the case that senior cat food was low protein, low fat, and high fiber (8), and the myth that senior cats need a diet low in protein still persists. Some health conditions may call for a low-protein diet, but a normal senior cat may suffer greater muscle loss with less protein (9).

Whether or not senior cats need more protein than adult cats is still unclear, however, and may depend upon the individual cat. If they are notably losing muscle mass, then a high-protein senior diet may be the solution (10). There are still senior diets made with low amounts of protein, all the way to those with enhanced protein, so it pays to check the label. Remember that it’s the dry weight of the nutrients that you need to compare, as the amounts on pet food labels are given in minimum and maximum percentages instead of absolute quantities. Check out this page for a rundown of how that math works.

Senior formulas may be low-calorie, hence the traditional wisdom of making them high-fiber, and for some cats this is appropriate. Generally, cats tend to have progressively slower metabolisms up to eleven years of age and are prone to obesity during middle age, around years six to eight (11). Once they get older than that, they often start to lose weight and may need high calorie diets (11).

Sometimes a vet may actually put a senior cat on a kitten diet if weight loss is a major issue, simply to get enough calories into them (8). In milder cases, a more calorie-dense senior food may be the way to go. If your cat has the opposite problem, well, low-calorie is where it’s at. Both obesity and being underweight can cause significant health problems or be symptoms of them, so keep a close eye on the body condition of older cats. If something changes, always have a vet check for disease before trying to treat the problem with diet alone.

There are other variables as well, such as dietary phosphorous and sodium, which sometimes matter for senior cats if they have certain health problems (9). If your cat has any health issues but they don’t require a medical diet, ask your veterinarian if there is anything you should be on the lookout for when choosing their food.

All Life Stages Cat Food

In order for a pet food to claim that it is “complete and balanced” for all life stages, it must meet the standards set by the AAFCO for both the growth and reproduction and adult maintenance stages. Because the minimums for certain nutrients are higher in the growth/reproduction stage, and there are only a few maximums, “all life stages” food may be too nutrient-dense for some adult cats (12). The food has to have enough nutrients for every stage of life, so it makes sense that what you end up with is more like the food intended for kittens and queens. They have higher nutrient requirements.

Opinions are divided, but I found that veterinarians seemed most inclined to think that food for all life stages was really not appropriate for adult or senior cats (12, 13). Pet food companies had the more mixed advice. Personally, I think all life stages food is great for keeping on hand if you find a stray cat or kitten you need to assist, as you never know what age they might be, and the extra nutrients are probably not a bad idea. It’s not what I would feed my cats at home, though.

Works Cited

  1. Paretts, S. (n.d.). What is the difference between kitten and cat food? The Nest. https://pets.thenest.com/difference-between-kitten-cat-food-6832.html
  2. ASPCA. (n.d.). Cat nutrition tips. link here
  3. John, B. (2019, November 19). Kitten food vs. adult cat food: What are the differences? IdleCat. https://theidlecat.com/kitten-food-differences/
  4. Association of American Feed Control Officials. (2014). AAFCO methods for substantiating nutritional adequacy of dog and cat foods: Proposed revisions edited per comments for 2014 official publication. PDF
  5. Syufy, F. (2019, November 4). How to choose the best kitten food. The Spruce Pets. https://www.thesprucepets.com/choosing-best-kitten-food-552267
  6. US Food and Drug Administration. (2020, February 28). “Complete and balanced” pet food. link here
  7. Chewy Pet Central. (2019, November 13). Cat food for all ages: How (and what) to feed your cat during every stage of life. https://petcentral.chewy.com/ages-stages-cat-food/
  8. Chewy Pet Central. (2019, December 10). The best senior cat food: A guide to feeding your older cat. https://petcentral.chewy.com/best-senior-cat-food/
  9. Freeman, L.M., Linder, D.E., and Heinze, C.R. (2016, March 8). When should I switch my pet to a senior diet? Tufts Clinical Nutrition Service. https://vetnutrition.tufts.edu/2016/03/when-should-i-switch-my-pet-to-a-senior-diet/
  10. Pittari, J., et al. (2009). American Association of Feline Practitioners: Senior care guidelines. Journal of Feline Medicine and Surgery, 11(9), 763-778. https://doi.org/10.1016/j.jfms.2009.07.011
  11. PetCoach. (n.d.). Do senior cats have different nutritional needs? https://www.petcoach.co/article/nutritional-needs-of-senior-cats/
  12. Coates, J. (2014, April 25). Are life stage dog foods credible? PetMD. https://www.petmd.com/blogs/nutritionnuggets/dr-coates/2014/april/debate-over-all-life-stage-dog-foods-31604
  13. Rock Veterinary Clinic. (n.d.). Understanding pet food labels. https://www.rockvetclinic.org/post/understanding-pet-food-labels.html

Published July 26th, 2020

Updated November 1st, 2020

Cat Care

Should cats drink milk?

mehshadoweye

Meredith Hemphill

mehshadoweye

Encyclopaedia Felidae now has a Patreon! Go to www.patreon.com/EncyclopaediaFelidae if you want to help support this content!

Two tabby cats drinking saucer of milk
Image by FotoRieth from Pixabay

I was recently watching a YouTube video–one of those funny cat compilations, you know the type. One of the clips included a cat being offered milk, and oh boy, did the comments go crazy. Everyone had an opinion about whether cats should drink milk or not. I’ve always heard that cats are lactose intolerant and shouldn’t have milk, but there were lots of people who disagreed. Certainly YouTube comment sections are not the place to obtain scientific information, but it sparked my curiosity. I had no idea there was so much debate about this topic, and now I wanted to find out the answer for myself.

Cats certainly seem to like milk. My parents have had two infamous ice cream thieves. And cats have been portrayed in media of all kinds happily lapping from a saucer of milk, for at least two hundred years and possibly going back to the Middle Ages, but I had some trouble verifying the dates of older images. Why do cats like milk so much, or are we imagining it?

It’s not an illusion. Dairy farmers noticed a long time ago that cats would get very excited about fresh cow’s milk. Cats are particularly fond of the cream that rises to the top of the fresh milk, as cats are naturally drawn to fatty foods that would help them survive in the wild where food is not guaranteed, and cream is certainly high in fat. It has also been demonstrated that cats relax while lapping milk (1), perhaps because it recalls pleasant maternal memories.

Brown and white calf
Intended recipient of cow’s milk – Photo by Couleur on Pexels

Unfortunately, the fact that cats like milk doesn’t mean they should drink it. Kittens drink their mother’s milk in order to gain vital nutrients and antibodies until they begin weaning. The milk of mammals contains a sugar called lactose, and infants produce an enzyme called lactase to break down this sugar which provides them with important energy for their development. As the kittens begin to eat solid food and less of their mother’s milk, they slowly stop producing lactase. The same is true of other mammals, including humans, but an unusual percentage of humans continue to produce enough lactase to digest dairy into adulthood. Cats, like other mammals, usually don’t. This means that most cats are lactose intolerant as adults.

Cats may enjoy milk or other dairy products while they’re eating them, but the majority who are lactose intolerant will pay for it later with gastrointestinal upsets. The undigested lactose can’t be absorbed into the bloodstream, so it moves straight through the intestines, drawing water with it and causing loose stools or diarrhea. They may also experience vomiting, and the action of intestinal bacteria fermenting the lactose can cause gas and bloating. Even cats that are not lactose intolerant may have dairy allergies that can also cause gastrointestinal and/or skin problems (2). Not the recipe for a happy cat, or a happy cat parent, for that matter.

Not all cats have this problem. There are some that can handle milk without an issue. Others are fine with small amounts from time to time but react negatively if given more. Regardless, it’s important to note that cow’s milk is not nutritious for cats even if they can tolerate it. It’s essentially junk food, high in calories but devoid of the protein and other nutrients that cats need. Obesity is a significant problem among pet cats. Whole milk especially poses a risk because it has so much fat. A well-nourished cat doesn’t need all that fat.

White goat
Goat’s milk can be a good treat for some cats – Photo by Ellie Cash on Unsplash

The healthiest cat treats are plain meat, cooked if you’re worried about contamination (which would be fair). Nutritious commercial treats can also be fine in moderation. However, if your cat is just crazy about milk, there are some options that are better for your cat. If you already know that your cat can tolerate lactose, then small amounts (think a teaspoon or so) of low-fat or skim milk as an occasional treat could be fine. Lower-lactose products such as plain yogurt or goat’s milk might also do. Goat’s milk has more vitamins and minerals than cow’s milk and contains the amino acid taurine, which cats require, so there’s a point in favor of the goats.

I have seen some claims that raw (unpasteurized) milk is preferable because the nutrients and enzymes present in the milk have not been heat-killed. I have also seen some information which suggests that it might be dangerous due to the presence of potentially harmful live microorganisms. Personally, I would err on the side of caution and choose pasteurized, but you can make your own decisions in the regard. Lactose-free milk products for humans are available, as well as “cat milk” products specially formulated for cats. They vary, but are generally lactose-free, low-fat, and more nutritious for cats. They are available online and at many pet stores. In any case, milk of whatever sort should be given only as a treat to adult cats, in small amounts.

Milk alternatives that should not be used include plant milks such as soy milk, almond milk, etc. Cats are carnivores and are not well-equipped to digest the carbohydrates in plants. Plant milks are often sweetened, and cats do not need all that sugar, either. Plus, it isn’t uncommon for cats to have allergies to soy.

In settling a great YouTube debate, it seems that cats should generally not drink milk, but there are cats who can handle it or other kinds of milk that cats can have. As long as it’s given as a treat, rather than used as a major part of their diet, a little dairy or an appropriate alternative can be okay. I would rather Rosie stayed out of my ice cream bowl, however.

Note: Kittens should never be given cow’s milk or any kind of alternative. They should only receive their mother’s milk or a kitten formula, if a mother isn’t available, until they are old enough for weaning.

Works Cited

  1. Cervantes, M., Ruelas, R., and Beyer, C. (1983). Serotonergic influences on EEG synchronization induced by milk drinking in the cat. Pharmacology Biochemistry and Behavior, 18(6), 851-55. https://doi.org/10.1016/S0091-3057(83)80004-5
  2. Guilford, W.G., et al. (2001). Food sensitivity in cats with chronic idiopathic gastrointestinal problems. Journal of Veterinary Internal Medicine, 15(1), 7-13. DOI: 10.1892/0891-6640(2001)015<0007:fsicwc>2.3.co;2
  3. Kornreich, B.G. (2020, May 2). Dear Elizabeth: Is feeding cats milk safe for your kitty? [Email newsletter] Cornell Feline Health Center.

Published on May 8, 2020

Updated January 2, 2021