High Carb Diets for Pets?
Carbohydrates – sugars, starches, and fibre – are sources of energy in common commercial pet foods, if used responsibly. However, irresponsible carb contents of current commercial pet food offerings is the reason for the current raw feeding debate taking place. That said, the body of the pet actually contains only small amounts of unused carbs; carbs in the diet that your fur kids do not need is stored as glycogen and body fat. Plants, however, contain a large amount of carbs and are included in most commercial diets to provide energy, fibre or as a filler.
Natural sugar and starches found in plants are useful for supplying energy and are more easily digested by your fur kids, given the correct source is selected. However, you should avoid feeding excess sugars, especially man-made sugars, that is often added by commercial pet food companies to increase the flavouring in processed foods. This is due to sugars competing with essential dietary nutrients for digestion and absorption, and in most cases, contribute to obesity. In the long term, high sugar contents may also predispose your fur kids to diabetes.
With a few exceptions, most dogs and cats have no established dietary requirement for carbohydrates. - this notion has been acknowledged by many academia as well as the U.S. Pet Food Manufacturer's Association [ref] (requires Adobe PDF Reader) themselves.
Once digested and absorbed by your fur kids, one of three things can happen to the sugars and starches: they are immediately used for energy, they are stored as glycogen in the liver (to be used in future time for energy), or they can be stored as fat.
Fibre is sometimes added to the diet to prevent both diarrhoea and constipation. In many commercial pet food formulas, fibre is added to help your fur kids feel full - like pigging out on McCarbs, but never really being satisfied after eating. In general, most cheaper pet foods often have too much fibre as a filler. As a result, pets can become full before consuming the needed nutrients and can exhibit nutritional deficiencies - but that is why you are hear to learn about more natural diets.
While both dogs and cats can digest and absorb carbs, neither has specific dietary requirements for this nutrient form. Cats especially, being true carnivores, do not need carbs in their diets. Cats are able to easily maintain blood glucose levels when fed high-protein, low-carb diets. The sugar transporting system of the cat’s intestinal system does not adapt to varying levels of dietary carbs as cats have low activities of intestinal disaccharidiases (sucrose and lactase) enzymes. Cats also only produce about 5% of the pancreatic amylase enzyme (the carbohydrate-digesting enzyme) that dogs produce. Also, unlike dogs, cats do not possess the liver enzymes activity (hepatic glucokinase), which limits their ability to metabolize large amounts of carbs. Many commercial cat foods contain large amounts of carbs (especially corn), which lower the price of the food. These foods should never be fed to cats, who require instead large amounts of animal protein and minimal amounts of dietary carbs.
Do you know how many carbohydrates are in your bag of kibble? Most pet parents don’t because the pet food manufacturer doesn’t really want you to know. Therefore, they don’t list it on the label !?
A crucial figure to know, seeing the pet obesity rate is soaring over 60% and cancer (needs glucose to thrive), is roughly 1 in 2 pets.
According to Association of American Feed Control Officials (AAFCO): “Carbohydrates are not measured directly, but can be estimated by calculating the “nitrogen-free extract” in the product. This is determined simply by subtracting the average of each of the other components (percent crude protein, crude fat, crude fiber, moisture AND ash) from 100.” If the ash is hidden, the general rule of thumb is between 5 to 8%, so pick a value.
However experts also say: “… fibre is actually a carbohydrate. So, its percentage is automatically included in your carbohydrate calculations.”
So let’s go with this guideline: Protein + Fat + Moisture + Ash, then subtract 100 = Carbohydrates.
After the calculations, pet parents are going to find that some of these bags of kibble have anywhere from 40% to 70% carbs in them! Still want to feed McKibble and McCan to your fur kids?
Below is an example of the calculation, having converted on of our commercial frozen BARF diets to dry matter (DM) first, and brand "X" science formulation using the calculations and guidelines from Dr. Becker in her article titled "The Things You NEVER Want to See on Your Dog Food Label..." [ref] and Dr Jean Dodds and Diana Laverdure, in their book titled, "Canine Nutrigenomics - The New Science of Feeding Your Dog for Optimum Health". In order to compare wet, canned and kibble, the correct method is to convert all to Dry Matter (DM) to ensure that one compare apples for apples.
|As Wet||As DM||Brand "X" Dry||As DM|
Converting as fed basis to dry matter (DM) basis
Fortunately, it’s not difficult to mathematically remove the water content from dog food products so that we can accurately compare their nutrient values. Dr Jean Dodds and Diana Laverdure describe it in simple steps in their book titled, "Canine Nutrigenomics - The New Science of Feeding Your Dog for Optimum Health". Here’s how to do it:
Subtract the percent of the food’s moisture content from 100 to determine the dry matter. In the example above, the kibble containing 14% moisture will contain 86% DM.
To determine the amount of protein on a DM basis, take the crude protein listed under the Guaranteed Analysis on the food’s label and divide that number by the DM number you determined in Step 1. If the food lists a guaranteed analysis of 21.8% protein (as per our example), for example, calculate 22 divided by 92, which equals 25.3%. In this example, the food contains 25.3% protein on a DM basis. You can use this same formula to determine the DM amount of fat and other nutrients as illustrated in the table above.
Let’s compare the protein content of this kibble with the protein content of a commercial deep frozen raw food containing 71% moisture, which contains 29% dry matter (DM) (100 – 71 = 29). According to the label’s Guaranteed Analysis, this food contains 12% protein on an “as fed” basis.
To convert the protein value to a “dry matter” basis, divide the 12% protein by the food’s 29% DM, which equals 41.4% protein.
We just learned that the raw frozen food contains more protein per kilogram on a DM basis than the kibble (41.4% compared to 25.3%), even though at first glance the kibble appears to have much more protein. This example illustrates the importance of converting nutrient values from an “as fed” to a “dry matter” basis when comparing foods. Otherwise, you simply cannot compare “apples to apples”.
If you do give your fur kids kibble or canned, knowing what’s in the food by understanding what’s on the label can help to optimize your dog’s health by feeding him more in keeping with the principles of nutrigenomics as promoted by Dr Dodds and Diana Laverdure.
The Really Big Carb Debate ...
Let's break down the "so-called" requirements for carbs in pet cuisine. The following text was taken from "Holistic Guide for a Healthy Dog", by Wendy Volhard and Kerry Brown [Amazon]. Their discussion of carbohydrates and the functions they perform seem to "prove" that most dogs need additional carbohydrates in their diet, a belief that is pervasive in most concepts of canine nutrition.
"In addition to providing energy, carbs maintain the health of the thyroid, liver, heart, brain and nerve tissue. They regulate how much starch and fat will be broken down and utilized. Once in the digestive tract and assimilated, they are stored in the liver in the form of glycogen, which controls energy balance. Low carb intake may cause cardiac symptoms and angina. The central nervous system requires carbohydrates for proper functioning as does the brain. The brain can't store glucose and is therefore dependent on the minimum supply of glucose from the blood. With insufficent carbs in the diet, protein and fat are converted to energy, weakening the immune system and preventing the body from building enough antibodies to fight disease. Poor hair growth and constant shedding are symptoms of carbohydrate deficiency.
Thyroid function is also dependent on the correct amount of carbohydrates in a dogs diet. B compounds found in many grains and strach producing veggies is needed so the amino acids phenylalanine and tyrosine can produce T3".
But do most dogs really need carbohydrates? In the Waltham Book of Dog and Cat Nutrition (2nd edition, 1988) [Amazon], we read that:
"There is no known minimum dietary carbohydrate requirement for either the dog or the cat. Based on investigations in the dog and with other species it is likely that dogs and cats can be maintained without carbohydrates if the diet supplies enough fat or protein from which the metabolic requirement for glucose is derived."
How can this be? Let us discuss just how the dog and cat are able to fulfil their requirement for glucose [ref] through a biologically specie appropriate diet of raw meat, bones, and organs.
Carbohydrates do provide quick and easy energy. However, it is not "carbs" that maintain the health of the organs listed in the quotes above, but glucose. Glucose can be obtained from both fat and protein through a process known as gluconeogenesis [ref], where amino acids and fat (not fatty acids; those use a different cycle) are "converted" to glucose. If carbs are present, though, they will be converted to energy first before fat and protein because they are easier to use. This is the reason that carbs regulate how much starch and fat will be broken down and utilized in your diet. If there is a plethora of carbohydrates, fat will be stored instead of used. If there are not enough carbs to fulfil energy needs, then fat will be converted to glucose and used. If no carbs are present, then fat and protein are used to fill energy needs. In humans, body fat stores are large, and contain about six times the energy of the protein stores.
Excess carbohydrates are stored in the liver and the muscles as glycogen [ref] AND in the body as fat. In humans, the body stores of glycogen is severely limited. However, since carbohydrates are not the only source of glycogen (which also comes from proteins and fats through a process known as glyconeogenesis), they are not absolutely necessary. Human athletes commonly perform "carbo loading" techniques where they eat huge carby meals of things like pasta to rapidly replenish their glycogen stores in their muscles and liver before a competition. The carbohydrates, when consumed in excess, are more rapidly converted and stored as glycogen compared to fat and protein. However, once again, fat and protein can also be stored as glycogen, which makes carbohydrates unnecessary unless you want to perform "carbo loading" (in conditions of spontaneous overfeeding, or "carbo loading", the entire excess fat intake is stored as body fat for reuse later). But, carbohydrates do not rebuild spent muscle tissue, etc;- Protein does that. Fat is also easily utilized for quick energy, too, and provides more energy per gram that carbohydrate does. The fat stores represent an energy buffer for the body.
It is not low carbohydrate intake that causes things like cardiac symptoms and angina; it is low blood glucose [ref]. If there is not enough glucose in the blood system, then you run into many problems including black outs, cardiac symptoms (like arrhythmia), and angina (chest pain). Of course, it is interesting that wolves and wild dogs can go without food for weeks and still survive well enough. How do they do that without eating carbs? Simple: they use up fat reserves and may even dip into their own muscle to get the necessary proteins and fats to provide glucose and energy for their bodies. So carbohydrates themselves are not actually necessary; glucose is necessary, and that can be obtained from protein and fat.
What about the brain? The brain is preferentially given glucose above all other organs [ref]. Glucose in its ready form, at that. But does this mean carbohydrates are necessary? Since glucose can be synthesized from fat and protein as well, then we have to surmise: no.
What about the claim of protein and fat - when converted to energy - weakening the immune system? This seems to be taken from human research where athletes in intensive training had suppressed immune systems which could be improved by consuming proper amounts of carbohydrate [ref]. Additionally, white blood cell production in humans seems linked to glucose production. More glucose present means the body is better able to mount an immune response - until there is "too much" glucose around and insulin spikes and starts suppressing all other pathways in the body except for those needed to force the glucose into cells (fat cells). High amounts of simple carbohydrates and sugars are known to suppress the immune system (though the Loma Linda study is suggestive, it is widely accepted that more research needs to be done on sugar and its possible immune suppressing effects). If this is the case, though, one could wonder how a diet high in grain affects our pets - overstimulation of the immune system due to high concentrations of glucose from the grain? Perhaps this is why many pets suffer "allergies" while on grain.
Our question: as long as the animal is receiving appropriate fat and protein, glucose production should not be hindered, correct? And for carnivorous animals like dogs, one can postulate and wonder if their white blood cells are more sensitive to glucose than ours - meaning, less glucose is needed to "stimulate" canine white blood cell production compared to human white blood cell production.
Using protein and fat for energy does not weaken the immune system unless there is not enough to go around, so to speak. If someone is starving, then using protein and fats for energy - while necessary - is a little "cost-intensive" on the body. But it is not the lack of carbs that is hurting them; it is the simple lack of enough food. Similarly, a human athlete in intensive training may overwork their body to the point that using protein and fats for fuel becomes too cost-intensive to their body.
What about poor hair growth and constant shedding resulting from a lack of carbohydrates? Can these indicate a "need" for carbs? Maybe, but more likely it indicates a need for better overall nutrition. We have not heard of "carbohydrate deficiency" in any animal, and a quick search online and PubMed has not revealed either. Why? Because there is NO SUCH THING as a "necessary carbohydrate", just necessary glucose. Our bodies, and our dogs' bodies, can do without carbohydrates (although one would say our dogs would fare better than humans, since we are omnivores who do well with fresh vegetables in our diet ...). Fats and proteins can be converted easily to necessary glucose. Poor hair growth and constant shedding are linked to an overall poor diet, poor consumption of essential fatty acids, biotin deficiencies, some vitamin and mineral deficiencies, AND a lack of good fats and proteins in the diet. Protein, not carbohydrate, is the building block for hair and skin and all other parts of the body. Carbohydrates do nothing for building and maintaining the body structures except provide easy glucose to fuel the rebuilding process.
What about thyroid function? Thyroid function is dependent upon the correct amount of glucose produced by the dog's body, not by the correct amount of carbohydrates in the diet. Too much glucose from easily available carbohydrate energy sources can cause just as many problems as not enough glucose. Since we have already established that glucose can be produced from fat and protein, then it would again seem that carbohydrates are actually unnecessary provided that there is enough protein and fat to go around.
Why then, a natural raw diet?
The most soluble and digestible carbohydrates are starches and sugars in plants. A starch's source and its degree and type of processing determines its availability. For example, dogs and cats can almost completely digest and absorb some starch, such as rice, however, more than 20 percent of other starches can not be digested. For example, the availability of starch in wheat, beans, and oats is poor. The availabilities of potato and corn starch are also much poorer than that of rice. Of the poorly digested carbohydrate sources all, except potato, are the most common ingredients in commercial grain-based pet foods, where they are the major energy source. The amount of carbohydrate in the food you feed your dog or cat has a crucial influence on the types of bacteria that are prevalent in its intestines.
Cooking determines starch digestibility and therefore its availability. Cooking increases the digestibility of all starches, especially raw potato starch, that is otherwise poorly digested by your fur kids. Availability of starch to action by digestive enzymes also influences digestibility. Enzymes cannot digest starch inside indigestible plant cell walls - in other words - whole or raw starch sources. Dietary fibre further reduces carb digestibility.
Dogs usually tolerate dietary starch, and small amounts typically cause few problems. Cats tolerate less dietary starch, however, provided that the maximum intake does not exceed four grams per kilogram body weight per day. Greater amounts of starch in the diet will cause diarrhoea. It is generally accepted that dogs can tolerate up to 2.5 times this amount, providing the starch is well cooked.
Sugars As a Source of Carbohydrate?
Sucrose is sometimes used in commercial grain-based pet foods. Sucrose is used as a preservative in semi-moist foods (wet or canned), and is found naturally in other food sources such as molasses, maple syrup and sugar, honey, fruits and vegetables. The intestine’s mucosal enzyme, sucrase, hydrolyses (convert) sucrose to glucose and fructose. Cats and dogs have adequate levels of sucrase activity to digest small amounts of sucrose, but excess sucrose is not completely digested and as a result can cause diarrhoea.
Lactose is normally found only in milk products, but is often used to coat some of the commercial puppy food offerings available today. Intestinal mucosal lactase hydrolyses (convert) lactose to glucose and galactose. Lactase activity is usually sufficient to digest small amounts of lactose in diets for adult fur kids. With little or no lactose in the diet, lactase activity decreases, as it is not required. With subsequent lactose consumption, lactase activity may be insufficient to digest lactose and diarrhoea develops as a result.
Sorbitol is found in fruits and has a sweetening power similar to glucose. Sometimes fur kids are given foods and medications containing sorbitol, however, sorbitol is the alcohol of sucrose. Intestinal absorption is poor for sorbitol and excessive amounts will result in diarrhoea.
Dogs may not readily digest galactosides [ref], carbohydrates found in dairy products and soybeans. They are digested by intestinal mucosal enzymes unique for galactosides. Enzyme activity may be low if little galactoside has been fed in the process to your fur kids. Feeding large amounts, in turn, will cause diarrhoea. Longer-chain carbohydrates (oligosaccharides) containing galactose, such as rhamnose, stachyose and verbascose, form about half the carbohydrate in soybeans. They resist digestion in the small intestine and are fermented by colonic bacteria. Fermentation always produces gas, so flatus is common in fur kids fed on these formulas. Fermentation also produces short chain fatty acids that support nutrition for colonic mucosa and promote salt and water absorption. Excess fatty acids can cause diarrhoea. What is common, however, with feeding excess digestible carbohydrates, is that the small intestine does not completely digest and absorb the food. Carbohydrates, other than those containing galactose, can cause digestive tract upsets when either the amounts in the diet are excessive or there is insufficient enzyme activity for their digestion.
Health Problems Due to High-Carbohydrate Diets?
Feeding high-carbohydrate diets can cause physiological abnormalities and signs of disease in pets. High-carbohydrate diets affect performance and nutritional state of working dogs. Some working dogs fed on high-carb diets cannot maintain normal weight, and their performance as herding, hunting or sled dogs shows reduced stamina and ability to work as a result (see our article titled "Nutrition for Working Dogs" for additional details). Diets containing excess carbohydrate that exceed capacities for digestion and absorption usually cause diarrhoea, abdominal distention (from gas accumulation) and flatulence (room clearing capabilities!). Poorer digestibility is evident on feeding uncooked carbohydrate (such as raw potatoes for example) and on feeding many of the cereals mentioned earlier. However, cooking can increase starch solubility and digestibility, but under-cooking also results in incomplete starch digestion. Cooking is important to solubilize carbohydrate in soybeans. It is also necessary to inactivate a protein that binds digestive enzymes and reduces protein digestion. If carbs are required in the diet, diets should be formulated with the most highly digestible carbohydrates available, keeping in mind though, with a few exceptions, most dogs and cats have no established dietary requirement for carbohydrates.
Some of this work was adapted from the works published by Carissa Kuehn, Myths of Raw Feed, https://rawfed.com/myths/.
Additional Articles and Videos
Good reference articles and further reading available at:
- Dr Jean Dodds and Diana Laverdure, "Canine Nutrigenomics - The New Science of Feeding Your Dog for Optimum Health" (Amazon);
- Cats and Carbohydrates: The Carnivore Fantasy? (PubMED)
- Pet food labels - what you don't see is important! Requires Adobe (Natural Pet Products);
- Do dogs and cats need grains? (Natural Pet Products);
- "Grain-Free" Doesn't Mean Carb-Free - (Mercola);
- What's Wrong With the Newest Grain-Free Craze? (Mercola);
- Gut microbiota of humans, dogs and cats: current knowledge and future opportunities and challenges (2nd Chance);
- Eating Fast Food Increases Calorie Intake and Decreases Nutrient Consumption (Human) by Dr Sam Girgis (Dr Sam Girgis);