Ultimate Theory on Nutrition for Dogs and Cats

Efroim Gurman, PhD, Dr.Sci.,

  1. Introduction

Our pets not only eat table scraps from human meals, they are also affected by the human approach to the theory of nutrition. This makes sense—the general ideas about the biochemistry and physiology of human nutrition are pretty similar to those of other mammals.

Nutrition is a popular topic. I wouldn’t be surprised to find out that popular interest in dieting and various nutrition philosophies was no less extensive than popular interest in sex issues. The science of nutrition has been mainstream in medicine, biochemistry, and physiology for millenniums and has accumulated a huge database of facts and effects. However, the average person seems to absorb a mess of popular terms without understanding them properly: “natural,” “organic,” “calories,” “vitamins” and many others that are thrown together in various arrangements by numerous sects of believers in more or less popular recommendations. No matter how weird some of these dietary cults really are you can always find strong adherents to “a new dietary theory.”

As a credentialed professional in the physiology of digestion and nutrition I spent my life trying to separate facts from illusions and to understand what is the best food for me, my family, and my pets. I can talk and talk about my beloved subject nutrition, but, unfortunately, in this age nobody would like to read multiple volumes. So, I will try to condense my thoughts on nutrition for cats and dogs to only the most important and scientifically proven ideas.






  1. Deep general thoughts about nutrition.

1.1. Paradigms of Nutrition.

Among numerous scientifically based theories of healthy nutrition there are several popular paradigms. One is the so-called Paleo Diet (PD).

The PD adheres to the pre-domestication history of canines and felines. This is fair and reasonable because thousands of years of natural selection certainly had a solid influence on the organism and its adaptation to food. In general, the core idea of the PD is attractive, but there are four caveats to consider:

1) Contemporary pure-breed or mix-breed dogs and cats have experienced significant evolutionary changes since coming to live under human supervision (keep in mind that a century for dogs and cats means about 50 generations, while for humans it is only about three or four generations—cats and dogs have a generational exchange nearly 15 times faster than that of humans);

2) Contemporary food sources are not equal to their ancient equivalents. (For instance, the meat of a hunted deer fed on wild vegetation is not the same as the meat of farm animals fed on contemporary animal feed—the difference is not only in the proportion of fat but in the content of numerous physiological agents; even fruits and vegetables today vary greatly from their wild predecessors. And the availability of food for current hunters and gatherers is very different. The efforts to gain this or that food are very different for wolves than they are for dogs. The natural food options for these now domesticated animals have been replaced by human food selection, etc.);

3) The lifestyle and environment for wild and domesticated animals is different (most pets do not suffer the extremes of hot or cold weather as their wild predecessors had);

4) And, the most important difference of all: a difference in life goals. While in nature, an animal’s main goal is to survive long enough to reproduce, pets do not have to think about survival in the same way. And for them, reproduction rarely bears any significance. Their longevity is largely for the benefit of their owners.

Followers of the raw food (RD) movement are not far from those who adhere to the PD theory. They also obey the idea of natural food for their pets but they stress such issues as the non-compatibility of artificial food processing with the natural digestion process. I fully agree with them on this point, but one needs to consider the above-mentioned points. Followers of RD are paying respect to the physiology of the gastro-intestinal tract but their recommendations often miss the fact that natural food available in stores is a poor imitation.

The Balanced Diet (BD) was a good achievement during the era of major biochemical discoveries. The tenets of the theory were more or less accurate, pointing to the existence of major food components (proteins, fat, carbs, essential vitamins and minerals), as well as the calories needed to sustain an organism’s functionality.

The core idea of BD is to balance the input and output of an organism. Most commercial food producers are now in a race to show customers that their food meets dozens (even hundreds) of these parameters. It might be great but there is only one big “but”…some critics take issue with commercial food because it is manufactured in bulk, processed with preservatives, and includes all kinds of fillers and by-products, antibiotics, urea, bone meal, sugars, lactose, corn, wheat and soy. These ingredients can and will wreak havoc on a dog’s or cat’s internal system, but, in my view, the main defect of such food is the damage to pets’ digestive systems from these artificial conglomerates of necessary (and unnecessary) molecules.

Another important thing with BD is uncertainty: what does balance mean, exactly? Should each bite be balanced? Or each meal? Each portion? Or the whole of a pet’s daily/weekly consumption?

There are a lot of websites, and other literature, that focus on balancing about a hundred ingredients. Their authors try to produce the impression that their calculations are THE right calculations. In my experience, complete balance is impossible—when you start to balance proteins and amino acids, the formula will never be absolutely accurate, as there are too many factors in play, and their relationships relative to one another are complicated. If you also take into account calories from fats, carbs or proteins, it becomes even more difficult, especially if you’re paying attention to the proportion of various ingredients within fat, carbs and proteins. Then this balance has to be extended to the proportions of dozens of minerals and vitamins and the final goal—a balance of everything in one food—becomes absolutely unrealistic even when working with computerized calculations.

BD was a widely popular theory until the end of the Twentieth Century until the Adequate Diet (AD) was proposed by the genius physiologist A. M Ugolev. The main difference between BD and AD consists in the replacement of a mathematical balance of input and output with basic supply and demand principles resulting from the natural biological needs of food consumption and digestion. What does this mean in simple words?

  1. a) Appetite is a great and important natural mechanism that drives an organism to fulfill its nutritional needs. This mechanism evolved to give animals a way to coordinate the amount of food intake with the specific needs of an individual. BD doesn’t take it into account, while AD considers appetite an important feedback mechanism for both the quantity and quality of food and a sign of nutritional health.
  1. b) Insoluble fibers, an indispensable component of natural food, are usually neglected by BD theoreticians while AD adherents note their role in digestion as part of the natural process. Indeed, from the point of view of BD adherents, these fibers, which enter and leave the gut in equal parts, are considered to be a useless feature. AD adherents, on the other hand, see them as part of the necessary habitat for the gut’s micro flora as well as the mechanical stimulus for the gut’s peristalsis.
  1. c) According to the BD theory, the intestinal micro biome is competing with the body for important food components. But AD theory considers microflora a necessary participant of the digestion process, which takes its price in the form of certain molecules and pays back with the elimination of others and the enrichment of intestinal content with some essential ones.
  1. d) The BD pinpoints molecules that enter and exit the gut as the only meaningful characteristic of successful nutrition. AD theory considers the digestive processing of food as a must for healthy nutrition. The theory considers the food in its journey from mouth to bowel. The role of the teeth; the salivary glands that wet the food in order to bring it to the necessary consistency; the taste receptors that signal to the brain about the food’s quality; the necessary stomach acid and the enzymes it contains; the food’s pH; the organism’s recording of the volume of the food consumed; the hormonal regulatory mechanisms excreted and stimulated by the liver and pancreas which are very important for the whole organism; the role of the bowel changing the chemistry of the content and adding many new molecules while eliminating others. Of course, in certain extreme situations a doctor can support an organism with vitally important substrates through intravenous injections but this way is far different from the normal way to nourish an organism.
  1. e) The BD theory attempts to balance food intake without accounting for the cycles of life, which are inconsistent and unstable. There are seasonal and individual cycles that vary for different substrates. AD theory is more natural because it takes into account the natural fluctuation over time.
  1. f) Within BD theory hunger results solely from a lack of food supply, but in nature the state of hunger ignites certain effects, such as the elimination of excessive storage, cleaning from less needed substances, the activation of behavior, etc. It should be mentioned that for carnivorous animals, hunger does not mean an empty stomach. For instance, when a wolf is hungry due to circumstance—because of bad weather, an unlucky hunt, or something like that—it gathers some vegetation, fruits, roots or less attractive leftovers, but can still remain hungry in spite of a full stomach.
  1. g) BD theory looks at food as a mixture of fuel and constructive materials. In reality, natural food also contains a long list of enzymes that aid with the digestion process. This phenomenon is called autolysis, sometimes referred to colloquially as “python’s dinner” because a python consumes the whole body of its prey without chewing, and the prey’s own enzymes work to digest its body. On the other hand, some food products contain agents whose natural role is to prevent digestion. Seeds are one such example, as they contain enzyme inhibitors in order to keep some of their proteins—carbs or fat—away from the organism that is consuming them, so that these proteins are passed along for the seeds’ offspring. Soy beans contain more protein than meat, but without the special processing, such as thermal treatment, which is necessary to kill the enzyme inhibitors they produce, the protein is unavailable to the carnivorous eater.












1.2. Instruments for adjustment.

For the practical use of even the best theory we need a set of methods in order to achieve results. There are several ways to adjust our pets’ nutrition so that they are receiving the optimal food. First, of course, it is to choose the best of available options according to the existing body of knowledge. Second, is to carefully monitor their appetite and their health conditions. And third is to use supplements to compensate for any scarcity in their diets.

The choice of better food sources depends on many social, economic, seasonal, and traditional factors, among other things. If you use prepared food, one can say that the best food will not come cheap. However, just because a food is expensive, it does not mean that it is good—higher prices can simply be the result of good marketing. It is very difficult, maybe even impossible to tell which of the reputable dog or cat food brands is the best, because their producers invest so much money and effort to make their brand number one, that the outward difference between each brand is practically negligible. Yes, you can pay attention to the percentage of protein, to the number of calories per unit, to other figures on a label, but there is actually no way to count the best proportion of valuable characteristics per dollar, per cup, or per meal.

Some companies declare the superiority of their pet food due to the numerous vitamins present. Yes, vitamins are important, but there is no scientifically proven data about the positive effects of added vitamins. Actually, vitamins first appeared when organisms detected that there was no need to build this or that molecule themselves because these molecules have always existed in food and it was “cheaper” for the organism just to get them in ready form than to keep the machinery for their construction. Of course, in a specific situation when food supply changes abruptly vitamins may come in useful—for instance in Southeast Asia, people used to eat unshelled rice that provided them with B12. But, once they started shelling the rice, B12 deficiencies became prevalent in the area. These were easily fixable through supplementation with B12.

Of course, it is more convenient for pet lovers to feed their pets ready-to-use commercial food but (see above) processed food is not what AD theory would recommend. Raw food, when it comes from reliable sources, is much healthier than prepared food.

In my opinion, the only way to determine the best possible food for your pet is to try the most prestigious brands and monitor your pets eating habits, behavior, and the appearance of their coat. Many reputable brands offer free samples—try them. Does your pet enjoy the food? How well does he or she digest it and is he or she healthy and happy after at least a couple of weeks eating it? If the answer to all of these questions is positive, then there is a good chance you chose the right brand.

The next powerful instrument to improve nutritional status is a feeding schedule that includes random periods of unloading similar to natural hunger. AD theory insists not to balance everyday input of food but to parcel out food based on reasonable life cycles, such as seasonal changes or the aging process. Of course, it is easier to do this when the owner prepares pet food in the home from raw ingredients rather than when the same commercial food is given meal after meal, day after day. For this reason, a very important instrument exists—supplements and treats. Supplements and treats interrupt the routine of the substances digested by your pet and can play a key role in supporting his or her health, even if they are consumed in smaller amounts than regular meals.

Thus, food choice, feeding style, and supplements are the main instruments to ensure a long and healthy life for your pet.

Above I tried to share a simple summary of the various nutrition theories and ideas. When distilled, these ideas don’t seem so sophisticated. Keep in mind that I did avoid presenting the numerous scientific facts behind them for simplicity’s sake. (I am a big fan of the subject and for those of you who are interested in deepening their knowledge with actual evidence, I’m happy to correspond anytime).

  1. Practical advice for dog owners

Now that you understand the foundations of healthy nutrition, which can be applied to humans as well as pets, let me tell you what regular pet-lovers can do for their canine buddies.

  1. Choice of food. The choice between prepared commercial food and homemade food, is for you, and you alone, to make. There are several pros to choosing commercial foods: it comes dry or in cans and is easier to store than keeping various food ingredients in your home; it saves time to have the food prepared for you; there is also some security in knowing that it was prepared by someone with expertise in the matter.

Homemade food lacks all of the above-mentioned conveniences, but with certain love and knowledge it might come closer to meeting your pet’s needs and desires. To get the maximum benefits out of homemade food, you have to pay attention to the sources of the ingredients you use. For instance, commercial food producers, as a marketing step, often declare that they do not use meat byproducts in the meaty portion of their food. This may seem like a good thing, but is actually a dubious practice. In the wild, animals eat the chitterlings first then the muscles. And this makes sense—the intestine, liver, spleen and other soft tissues contain a lot of enzymes and active ingredients. The gut has to be loaded with these enzymes in order to allow for better digestion of the muscular meat.

Regarding the list of ingredients in a food—the more the better. There is no such thing as the perfect food source—each ingredient has its pluses and minuses. There is no way to get the benefits without getting the drawbacks, too. So, the diversification of food sources raises the chances that the sum of minuses will not reach a dangerous level.

The consumption of organs and entrails ensures the additional consumption of vegetarian product that has been ingested by herbivorous prey and adds to the vegetation already consumed in the canine’s natural diet. Wild canines are able to choose herbs, vegetables and fruits according to their taste and smell—definite indicators of the presence of physiologically active ingredients. To imitate this side of healthy feeding there is point B.

Table 1: Dog’s macro- and micro-nutrient needs



NutrientsUnitsGrowth &AdultMaximum
Crude Proteing56.345.0

Proposed Revisions Edited per Comments for 2014 Official Publication

Crude Fat bg21.313.8
Linoleic acidg3.32.8
Eicosapentaenoic +NDc
Docosahexaenoic acidg0.1
Docosahexaenoic) acid Ratio30:1
Ca:P Ratio1:11:12:1
Iron dmg2210
Copper emg3.11.83
Vitamins & Others
Vitamin AIU1250125062500
Vitamin DIU125125750
Vitamin E fIU12.512.5
Thiamine gmg0.560.56
Pantothenic acidmg3.03.0
Folic acidmg0.0540.054
Vitamin B12mg0.0070.007



  • Recommended concentrations for maintenance of body weight at an average caloric intake for dogs of a given optimum weight.
  • Although a true requirement for crude fat per se has not been established, the minimum concentration was based on recognition of crude fat as a source of essential fatty acids, as a carrier of fat-soluble vitamins, to enhance palatability, and to supply an adequate caloric density.
  • ND – Not Determined. While a minimum requirement has not been determined, sufficient amounts of omega-3 fatty acids are necessary to meet the maximum omega-6:omega-3 fatty acid ratio.


  • Average apparent digestibility for iron associated with recommended minimums is 20% of that consumed. Because of very poor apparent digestibility, iron from carbonate or oxide sources that are added to the diet should not be considered in determining the minimum nutrient concentration for iron.


  • Because of very poor apparent digestibility, copper from oxide sources that are added to the diet should not be considered in determining the minimum nutrient concentration for copper.


  • It is recommended that the ratio of IU of vitamin E to grams of polyunsaturated fatty acids (PUFA) be >6:1. A diet containing 50 IU of vitamin E will have a ratio of > 0.6:1 when the PUFA content is 83 grams or less. Diets containing more than 83 grams of PUFA should contain an additional 0.6 IU of vitamin E for every gram of PUFA.


  • Because processing may destroy up to 90% of the thiamine in the diet, allowances in formulation should be made to ensure the minimum nutrient concentration for thiamine is met after processing.






  1. Supplements, minerals, vitamins. No matter how an owner chooses to feed his or her pet, supplements play a vital role in creating a healthier style.

Supplements and treats usually make up 1/10 or less of a pet’s daily food intake—usually much less. But, their role in promoting the health of a pet is substantial. In some ways, the macro nutrients that our dogs consume by weight are replaceable. With more or less accuracy one source of meat or calories can be replaced by many others. In the case of specific ingredients (supplements) that have to be included in small doses in order to ensure a better healthier life, these have to be in the diet without any doubt. I am not a big fan of vitamins, they may be helpful if a deficiency of a certain vitamin is observed (which in practice happens very rarely), but if there is no significant deficit, then an overload of it will have no added benefit for the organism, and can even be harmful and cause toxicity or overdose.

Minerals are similar—regular food sources usually contain the necessary minerals in sufficient amounts. And in the case that a real deficit of vitamins or minerals occurs in a dog’s organism, they are able to compensate for the shortage metabolically and the change in the animal’s food behavior (appetite, food preference) will be nearly as obvious as the blood results.

Physiologically active ingredients, which are usually the main reason to add supplements and functional treats, are another story. Without deep intrusion into the chemistry of physiologically active ingredients we might say that some of them play roles of hormone- or drug-like substances and signals. Even a few molecules can make a difference. Many renowned herbs are the predecessors of a contemporary pharmaceutics, but in natural form their action is softer and often free of side effects (which exist with the administration of any artificial drug).

What kind of supplements does your dog need? It depends on the concerns of the owner and the specific of age, breed, and health condition of your pet. Aside from certain issues (like immune deficits, allergies, level of activity etc.), where there is one obvious herb to use, it is generally better to use a multi-herbal composition for general health. The same applies to functional treats. Treats, in general, are a good training tool essential for socialization and the balance of positive/negative emotions.

VetVittles takes the value of treats to the next level by adding the health-improvement effects of herbal supplements. The company offers several treats of varying tastes, loaded with herbal extracts. These treats will not only please your pet’s taste buds, but also offer a range of health benefits.

  1. Feeding timeframe. A simple and effective way to improve nutrition is the manipulation of your pet’s feeding schedule and routine. Eating has to be a pleasant event for your pet, that is why it is not great to have a constant food supply readily available to your dog at all times. For instance, it is best when dinner is given after exercise, before your dog takes a rest. The digestion of food is work for a dog’s organism so it is good to let him or her sleep after the main course.

When creating a feeding schedule, we should also consider some valuable lessons from the wild, where dogs and cats were not always successful in obtaining game after a hunt. Mother nature took this into account, and even used it for the animals’ benefit—if hunting failed, the animals would be forced to scavenge for berries and other vegetarian replacements. These fiber-rich snacks would prepare the gut for the next day’s hunt and allow it to expunge harmful substances. Just recently researchers identify molecule with anti-aging effects on vascular system. This molecule produced from fat during fasting or calorie restriction.

Given this history, I recommend that once a week or so, you create an “unloading day” for your buddy—reduce your dog’s food portion to a tenth of daily consumption or even replace regular food with a vegetarian option. Such “days of hunger” are also a good time for supplements and treats.

  1. Practical advice for cat owners

For the cat owners our recommendations are mostly the same as for dogs, except for a few things specific to cats. Cats are usually more conservative in their food preferences. Yes, once in a while (it is better to do this during changes of season) give your cat the possibility to revaluate their preferred brand of food. Another specificity to felines is that in the wilderness most of them eat their prey intact, including the skin, hair, or plumage, and intestinal contents. They are usually very picky in their choices of herbs and that is why they may refuse to eat supplements even when they are necessary. For this situation, there is a simple trick—put a supplement on their paw or just smudge it on their fur: the cat will lick its coat and a portion of the supplement will get inside.

Table 2. Cat’s macro- and micro- nutrient needs.






NutrientsUnits perGrowth &AdultMaximum
kcal MEMinimumMinimum a
Crude Proteing7565
Crude Fat bg22.522.5
Linoleic acidg1.401.40
alpha-Linolenic acidg0.05NDc
Arachidonic acidg0.050.05
Eicosapentaenoic +

Proposed Revisions Edited per Comments for 2014 Official Publication

Magnesium dg0.200.10
Iron emg20.020.0
Copper (extruded) fmg3.751.25
Copper (canned) fmg2.101.25
Vitamins & Others
Vitamin AIU166783383325
Vitamin DIU70707520
Vitamin E gIU1010
Vitamin K hmg0.0250.025
Thiamine img1.401.40
Pantothenic acidmg1.441.44
Folic acidmg0.200.20
Biotin jmg0.0180.018
Vitamin B12mg0.0050.005
Taurine (extruded)g0.250.25
Taurine (canned)g0.500.50


  • If the mean urine pH of cats fed ad libitum is not below 6.4, the risk of struvite urolithiasis increases as the magnesium content of the diet increases.
  • Because of very poor bioavailability, iron from carbonate or oxide sources that are added to the diet should not be considered in determining the minimum nutrient concentration.


  • Because of very poor bioavailability, copper from oxide sources that are added to the diet should not be considered in determining the minimum nutrient concentration.
  • Add 10 IU Vitamin E above the minimum concentration for each gram of fish oil per kilogram of diet.


  • Vitamin K does not need to be added unless the diet contains more than 25% fish on a dry matter basis.
  • Because processing and specific ingredients may destroy up to 90% of the thiamine in the diet, allowances in formulation should be made to ensure the minimum nutrient concentration is met after processing.


  • Biotin does not need to be added unless the diet contains antimicrobial or anti-vitamin compounds.

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