Looking closely at the ‘dry food for healthy teeth and gums’ myth
I have been working with a client and her two lovely Maine Coons. On my last visit I gave her a wealth of nutritional advice regarding the natural diet of a cat which is meat. I turned up today to groom one of her cats under sedation, due to the cat having a massive phobia against being groomed, and was very happy when my client arrived with a huge bag of lovely wet food such as Lilys Kitchen and Thrive Complete. Hurray I thought. A client has actually listened to me and taken my advice :-). Upon arriving at her vets, and once the cat was asleep ready for me to work on, I heard the vet tell my client that her cat had plaque and that she should be buying kibble (dry food) to help ‘clean’ the teeth which would help the plaque problem. Once again I am listening to a client being told something which has had very little study and seems to be an untruth. So, I have decided to do some research on this subject and would like to highlight the following facts about the whole kibble cleans cat teeth statement.
- Lets look at the structure of the cat’s teeth. The cat has two sets of teeth during its lifetime – 30 permanent teeth. Each upper and lower jaw has three pairs of incisors and a pair of elongated and laterally compressed canine teeth. The function of the incisors is for grooming and tearing prey, whereas the canines are adapted for grasping and killing. Behind the canines are the premolars and molars. The cat has three pairs of upper and two pairs of lower premolars and one pair of upper and one pair of lower molars. The back molars are flat and provide shearing action for cutting food into small pieces before swallowing. These few molars provide VERY LIMITED ability to masticate food. Cats swallow bites of food with little or no chewing. A cats teeth are wholly designed for holding and killing small prey animals and are less efficient in chewing and grinding food (typical of most obligate carnivores (1). Now that the cat carer understands the anatomy of a cat’s mouth I can hand over to the wise words of Dr. Fraser Hale, DVM, a veterinary dental specialist, in his lecture given to the World Small Animals Veterinary Association.
It has long been felt that feeding a cat or a dog a dry kibble diet is better for the teeth than feeding them a processed, canned diet. The logic goes that dry food leaves less residue in the mouth for oral bacteria to feed on and so plaque would accumulate at a slower rate. Despite that, many animals fed on commercial dry diets still have heavy plaque and calculus accumulations and periodontal disease. This is because most dry pet foods are hard but brittle so that the kibble shatters without much resistance and so there is little or no abrasive effect from chewing (2)
2. Lets look at the typical advertising stance of dry food ‘Kibble can help to scrape tooth surfaces clean and the pressure of crunching the pieces strengthens tooth roots’. Jean Hofve, a hollistic feline veterinarian states:
Most cats don’t consistently chew dry food; they swallow it whole. Obviously, without contacting the teeth, there is zero effect on tartar accumulation. For cats who do chew dry food, whether consistently or occasionally, there is still little or no benefit. The kibbles shatter, so contact between the kibble and the teeth occurs only at the tips of the teeth. This is certainly not enough to make a difference in the formation of tartar and plaque, which most commonly builds up along (and underneath) the gumline at the base of the teeth.
She goes on to explain further:
In my experience as a feline veterinarian, I’ve probably examined at least 13,000 cats’ mouths. There was no real pattern to the dental and periodontal disease I saw. If anything, tartar and gum disease seemed to be more attributable to genetics or concurrent disease (such as feline leukemia or feline AIDS) than to any particular diet. I saw beautiful and horrible mouths in cats eating wet food, dry food, raw food, and every possible combination. Many of my patients initially ate mostly or exclusively dry food; yet these cats had some of the most infected, decayed, foul-smelling mouths I saw. If there was any dietary influence at all, I’d say that raw-fed cats had better oral health than cats on any type of commercial food. However, the overall effect of diet on dental health appeared to be minimal at most.
3. Many brands state that their ‘Unique kibble scrubs away laden plaque in the mouth to promote systemic health’. Dr. Steven J. Bailey, who founded Exclusively Cats Veterinary Hospital in 1992, states that:
Once the plaque has hardened, it seems a professional dental cleaning is the best way to get the teeth clean again…. The reality of feline dental disease is that genetics has a large part to play in your cat’s oral health, just as it does in humans.
Quote from a brand of dry Large kibble …”has been proven to help prevent tooth decay in cats” Again feline veterinarian Jean Hofve goes into great detail about this after studying the facts and which companies were behind certain ‘studies’. It’s a long read but here goes:
If your vet still believes the myth of dry food and dental health (which is still actively promoted by the pet food companies despite the utter lack of scientific support for the theory), here are a few references that refute the idea:
* Logan, et al., Dental Disease, in: Hand et al., eds., Small Animal Clinical Nutrition, Fourth Edition. Topeka, KS: Mark Morris Institute, 2000, p. 487. “Although consumption of soft foods may promote plaque accumulation, the general belief that dry foods provide significant oral cleansing should be regarded with skepticism. A moist food may perform similarly to a typical dry food in affecting plaque, stain and calculus accumulation…Typical dry dog and cat foods contribute little dental cleansing. As a tooth penetrates a kibble or treat the initial contact causes the food to shatter and crumble with contact only at the coronal tip of the tooth surface…The kibble crumbles…providing little or no mechanical cleansing….” The author also reviewed two studies on cat “dental” treats which showed “no significant difference in plaque or calculus accumulation with the addition of dental treats to either a dry or a moist cat food.” Of course, this book was produced by Hill’s, so it heavily promotes t/d. However, although t/d provided a “statistically significant” improvement, when you look at the actual graphs, the difference between Dog Chow and t/d is not impressive.
* “…When comparing dry food only and non-dry food only fed dogs…there is no pattern to the trends (some teeth show an apparent protective effect from feeding dry food only, and others show the opposite — for calculus index, the trend is protective for all five teeth in dogs feed dry food only, whereas for gingival index it is the opposite, and it is mixed for attachment loss). All maxillary teeth are significantly less likely to be mobile in the dry food only group, yet the mandibular first molar tooth showed the opposite effect.” Harvey et al., Correlation of diet, other chewing activities and periodontal disease in North American client-owned dogs. J Vet Dent. 1996 Sept;13(3):101-105. Logan (above) assessed this study as follows: “In a large epidemiologic survey, dogs consuming dry food alone did not consistently demonstrate improved periodontal health when compared with dogs eating moist foods.”
* There is an excellent review of the literature by A. Watson (Diet and periodontal disease in dogs and cats. Aust Vet J. 1994;71:313-318). This study is fully of interesting historical items. For instance, one study of cat skulls found evidence of severe periodontal disease in 25% of 80 cats; 75 of the skulls dated from 1841 to 1958, and 2 were from Egypt during the time of the Pharoahs!
* According to the above review, many of the early studies showed less tartar formation with hard dry food vs the same food mixed with water, and similar results were reported in a study with canned vs dry cat foods. In 1965 a study compared feeding raw whole bovine trachea, esophagus, and attached muscle and fat, vs the same food minced. Plaque and gingival inflammation were increased with the minced diet. Even more fascinating, they tube-fed the minced food and found that plaque and gingivitis did not decrease, “showing food did not need to be present in the mouth to induce these changes.” In fact, gingivitis tended to increase when cats were tube-fed, “suggesting that even the minimal chewing required with minced food had some cleansing or protective effect.” Minced food is similar in texture to canned food.
* A couple of studies showed that *large* dry food biscuits (not kibble) actually removed tartar, which is probably the theory underlying t/d’s oversized chunks. Feeding of half an oxtail accomplished the same thing when fed weekly in another study. (I can just see it now, “Brand X’s Tartar Control Oxtails.”) The study also noted that “No harmful effects were observed from feeding oxtails to > 200 dogs for > 6 years.”
* Gorrel and Rawlings (The role of tooth-brushing and diet in the maintenance of periodontal health in dogs. J Vet Dent. 1996 Dec;13(4):139-143) state that: “In a previous study, we showed that the daily addition of an appropriately designed chew to a dry food diet is effective in reducing accumulation of dental deposits…the addition of the chew to the dry food diet also reduced the severity of gingivitis that developed, compared with the regimen of dry food diet alone.” This points out that dry food does not prevent tartar/gingivitis without additional treatment.
* Interestingly, Gorrel states in another article that “The consensus is that supragingival calculus per se is not directly involved in the etiology or pathogenesis of [periodontal] disease, and is mainly of cosmetic significance if plaque removal is adequate.” (Periodontal disease and diet; J Nutr. 1998;128:2712S-2714S.)
* A more recent review (DuPont G. Prevention of periodontal disease. Vet Clin N Amer. 1998 Sept;28(5):1129-1145) says, “In some dogs, dry kibble or fibrous diet helps slow plaque accumulation more than does soft or canned food…Other chewing behaviors may be even more important for reducing plaque than is feeding dry food.” Not exactly a ringing endorsement of dry food! He cites 2 studies showing Hill’s t/d to be effective for “decreasing plaque and calculus accumulation.”
* A review of feline neck lesions found no significant influence of diet. (Johnson N, Acquired feline oral cavity disease, Part 2: feline odontoclastic resorptive lesions. In Practice. 2000 Apr:188-197).
These studies show that dry food does not clean a cat’s teeth any better than eating pretzels cleans ours! At best, we can say that dry food tends to produce slightly less tartar than canned food. For cats, the benefits of feeding canned food far outweigh any possible dental problems that may result. After all, it is much easier for your vet to clean your cat’s teeth once a year than to treat diabetes, urinary tract problems, and other diseases that are either directly caused or aggravated by feeding dry food.
Regular home and veterinary dental care are real keys to keeping your cat’s teeth and gums healthy for life.
5. I can conclude with common sense from the very wise words of Bronwyn Reijnders (BSc (Hons)) who is a departmental tutor at the University of Pretonia, South Africa whose areas of expertise are Animal Science and agriculture:
I find it common sense that commercial diets don’t promote dental health. Dogs and cats have plaque and sewer breath, while wolves and lions have pearly whites.
The difference? In the wild, both facultative (canine) and obligate (feline) carnivores chew the hide/feathers, sinew and bone of their prey. This keeps their teeth clean and provides some minerals and indigestible fibre.
To a large extent, I blame poor feed: the vast majority of kibble is grain based and utterly inappropriate for dogs’ and cats’ dietary requirements. Aside from that, grains are mostly carbohydrates… SUGARS, providing a ready energy source for oral bacteria to grow.
There is a reason kibble is brittle and shatters easily: it considers the lack of ability of dogs and cats to chew. Doubtful? Anyone who has ever given a jelly tot (or similar) to their pets knows this. The dog or cat will make exaggerated chewing motions, usually opening their mouths wide, licking their chops repeatedly and salivating. Amusing to observe and illustrating the point: we eat those sweets with ease, grinding our molars to crush them and using our tongues to dislodge them if they get stuck. Dogs and cats cannot.
When dogs and cats “chew” kibble, all they are doing is breaking a big lump into manageable pieces. If it was presented in small enough crumbs, they would just lick it up and swallow.
She goes on to say:
Noticeably in humans, when we eat small particles we still chew, even if it’s just a little. Dogs and cats are designed to swallow larger chunks whole, while we are designed to homogenize whatever we put in our mouths. The reason for this is physiological: nutrients are easier and faster to obtain from animal material (meat) than plant material. Mashing up the food allows omnivores and herbivores to extract maximum nutrition from their plant-based foods by providing maximum surface area for digestive enzymes to function. Plant cells have tough “walls” protecting their contents, while animal cells do not. Simplistically speaking, the cell contents are what provide the nutritional value, so any animals that get their nutrients from plants need to be able to break those cell walls and hence have flat, grinding surfaces to their teeth. Carnivores don’t face that problem, so a simple slicing mechanism is sufficient for their needs.
To conclude: any kibble that relies on grinding action to clean the tooth surface is ignoring the basic, fundamental anatomical and physiological characteristics of a carnivore.
Many thanks to the following for their expertise in cat care.
1. Linda P Case ( Teaches companion animal science at the University of Illinois)
2. Dr. Fraser Hale (Veterinary dental specialist)
3. Jean Hofve (Veterinarian)
4. Dr Steven J Bailey (Veterinarian-founded Exclusively Cats Veterinary Hospital in 1992)
5. Bronwyn Reijnders BSc (Hons) – Tutor at University of Pretonia – Animal Science and agriculture.
Thank you for reading. Should you wish any further advice regarding your cat please do not hesitate to contact firstname.lastname@example.org