Discussion: DCM and Homemade Diets- Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

Published June 2020, “Review of canine dilated cardiomyopathy in the wake of diet-associated concerns”, can be read here. This post is a general discussion of the paper and what we might consider when formulating homemade fresh food diets. This post does not discuss diagnostic measures, therapeutic formulations, or advice for selecting commercial diets. 

The review analyzed studies and provided a lengthy section covering nutrients and food sources. The review was NOT a study. There will be many more studies to review in the future as we learn more about dogs and their unique needs!

This post is my initial personal response to the paper. Please read the paper and not just what I have written here. 

This post also assumes the reader is familiar with methionine, cysteine, taurine, and carnitine. It also assumes the reader is familiar with using nutrient requirements. Please see the Raw Fed & Nerdy Full Course if not. This post also assumes general knowledge of DCM.

NOTE: I am continuing to refine this piece. Please check back with time. Again: This post is NOT discussing whether you should or should not feed a grain free diet or that area in general. This is a post relevant to people who feed homemade.

This post is geared more towards those who formulate diets using nutrient guidelines. This is not a commercial food post discussing grain-free diets.

6/18/20: I am aware of the funding of the review. Like many reviews and studies pertaining to pet food and nutrition, funding often comes from pet food companies. I personally feel that bigger brands, such as Purina, more clearly state their direct funding. It is also why I choose to focus on which parts are applicable to homemade formulation.

SUMMARY OF GENERAL CONSIDERATIONS WHEN FORMULATING PROACTIVE DIETS FOR HEALTHY DOGS BY FEED THY DOG
(Not for therapeutic use! |  Do NOT supplement without auditing the diet first! Many whole foods are options!)

I strongly recommend reading the full explanations provided below the chart. These are general recommendations that are not going to fit every dog.

The context of below assumes that the person reading know show to use nutrient requirements as these are used to analyze nutrient levels in homemade formulations. If not familiar, I recommend taking the Raw Fed and Nerdy Course.

I recommend that all diets are formulated using nutrient guidelines. If you are already making well-formulated homemade diets using nutrient guidelines and understand the nuances of formulation, you may find that this post only reinforces what we already know to be important 🙂

Taurine & Carnitine

Significance

Low taurine can cause DCM. Please see the Taurine section for lengthy discussion. Taurine synthesis and absorption can be disturbed in some breeds Carnitine is also needed for the heart to use energy. Synthesis of carnitine can be affected by suboptimal nutrient intake.

Personal Approach

Sulfur contains amino acids from animal based foods. When cooking, do not overcook. Taurine supplementation in cooked foods. Raw diets contain taurine, especially in heart. Taurine supplementation is often provided for some breeds. I do not agree that a blanket statement should be made about general supplementing for all at-risk breeds. See genetics discussion and causes of DCM section.
Carnitine is rich in meat. 

Diets primarily using kangaroo and rabbit are considered at risk because of low levels of taurine precursors.

Carnitine: Animal-based diet. Microminerals should be met from bioavailable sources. See zinc, copper, selenium, iron

Fiber & The Gut

Significance

High fiber diets reduce digestibility of the diet which can affect vitamins, minerals, and amino acids. However, some amount of fiber can be useful in promoting a healthy gut microbiome. The gut has been found (in other species) to be the location where sulfur containing amino acids are metabolized.

Personal Approach

Healthy dogs typically do well with fiber ranging from 1-5% DMB. A combination of insoluble and soluble fiber can be beneficial for elimination and gut health. High fiber diets using insoluble fiber can cause absorption issues of taurine and essential nutrients. Overall gut health should always be a consideration for every dog.

Potassium

Significance

While demonstrated of more importance in cats, potassium should still be provided at optimal levels in the diet.

Personal Approach

Make sure the diet contains enough potassium. Potassium can come up short in homemade diets. Consideration of how much sodium is in the diet is important. It is not that sodium is an issue for healthy dogs, it is that high sodium and low potassium may be problematic when viewed in their amounts relative to each other.

Choline

Significance

I strongly recommend reading the full choline section. Choline is required to regenerate methionine, metabolize fatty acids, and digest fat. It is a critical nutrient for the liver and bile. All of these factors can play a role in DCM. 

Personal Approach

The diet should be providing abundant amounts of methionine and folate. I personally only use food forms of choline to avoid potential negative effects on the gut. Eggs provide plenty of choline. While I still do not feel that the RA for choline always has to be met, I do not recommend ever that the diet be low in choline. Therapeutic cases will be different. 

Methionine and Cysteine

Significance

These sulfur-containing amino acids are used to create taurine. High heat and low quality sources of these amino acids can affect the synthesis of taurine. Many things can affect taurine synthesis, such as breed (or genetics in general), dog size, and mineral status. 

Personal Approach

Methionine and cysteine need to be provided from high quality sources in abundant amounts for all dogs. Diets heavy in rabbit and kangaroo may be at more risk for low levels of these nutrients. Diets, including raw diets, that are low protein can result in low intake of methionine and cysteine. High fat raw diets fed to dogs with low energy requirements can result in sub-optimal amino acid intake..

Iron

Significance

Required for many metabolic processes- including the synthesis of taurine and carnitine. 

Personal Approach

Use heme iron from animal products. Homemade diets that do not use plenty of red meat should be audited. Small amounts of spleen can easily boost iron. Chicken heart is also rich in iron. If using the RFN sheet, adjust bioavailability settings for plant based sources.

Zinc

Significance

Required for many metabolic processes- including the synthesis of taurine and carnitine. 

Personal Approach

Is often low in homemade diets. Red meat and eastern oysters are rich in zinc. Do not supplement zinc without auditing the diet first. Blind zinc supplementation to a raw diet just because it is often low can hurt copper status.

Copper

Significance

Required for many metabolic processes- including the synthesis of taurine and carnitine. 

Personal Approach

Very rich in ruminant based liver (beef, lamb for example). Relying on pork, chicken, turkey liver can often mean there is not enough copper in the diet. Other ingredients will need to be used to provide copper. Do not supplement without a diet audit!

Thiamin

Significance

Deficiencies in other animals has resulted in heart conditions.

Personal Approach

Homemade diets are often low in thiamin. Audit the diet. Pork is rich in thiamin. Some duck is relatively (compared to other animal products) rich in thiamin as well- but diet of the animal being consumed is important. Be aware of thiaminase sources in the diet. See vitamins and minerals course for full discussion.

Selenium

Significance

Deficiencies in other animals has resulted in heart conditions. Also works with Vitamin E (see below)

Personal Approach

Selenium from animal foods is more bioavailable. Plant based sources need to be prepared correctly (blended very well or cooked). The form is still less ideal. Selenium levels in soil vary a lot! Kidney is a fantastic source of selenium.

Vitamin E

Significance

Required to scavenge free radicals and works with glutathione. Low in dogs with DCM

Personal Approach

Diets high in polyunsaturated fatty acids require more vitamin E. Vitamin E is easy and safe to supplement with and is often needed in homemade diets. D-alpha tocopherol with mixed tocopherols should be used.

Glutathione

Significance

Works with selenium and vitamin E scavenge free radicals. Low levels found in dogs with DCM and is needed for cysteine synthesis.

Personal Approach

Provide amino acids abundantly as described above. Meat is very rich in glutathione.

 

Genetics, Other Diseases, and DCM

Genetics plays a role in DCM, but it is not straightforward. Genetic factors vary from breed to breed. Affected genes can vary as well. Because genes have different functions, each affected gene will result in different pathways leading to DCM. In other words, approaching all breeds with a genetic predisposition to DCM- and not just taurine-deficient DCM- the same oversimplifies the situation. For example, some breeds, such as the golden retriever, may have an overall different taurine requirement. Other breeds, such as the boxer, may experience deletion of a certain gene (STRN) that results in DCM. However, the nature of the disease and approach is very different. Doberman Pinschers can experience changes to PDK4. The function of each gene is different and simplifying the preventative approach to just supplementing at risk dogs with taurine overlooks a large genetic component and the different causes of DCM entirely. That being said, there are times, when considering certain breeds, when taurine should be directly looked at, among other genetic and dietary factors.

Furthermore, mixed breed dogs can still be at risk for hereditary DCM. 

The chart used in the paper is a fantastic visual of how diverse the etiologies of DCM is. I won’t write covering each category and will touch more on the nutritional part of the paper. Though, all parts of the paper are worthwhile to read. DCM can certainly occur secondary- such as is the case with hypothyroidism and other diseases listed below. Each disease in and of itself can affect nutrient requirements.

NUTRITION AND RELATION TO FRESH FOOD DIETS

Diets low in protein, taurine, and/or taurine precursors:

Not surprisingly, low protein diets have been linked to DCM- even when AAFCO requirements were met.Studies cite that supplementation of taurine and l-carnitine resulted in the reversal of the condition. This is important to consider. As we mention frequently, meeting nutrient guidelines (whether it be AAFCO or NRC or FEDIAF) does not mean that the protein is coming from high quality sources or that the diet is well-formulated. A case of two dogs eating a soy based diet met AAFCO requirements. Soy is lower in sulfur containing amino acids and devoid of taurine. Homemade diets, in the vast majority of cases, should both use nutrient requirements but meet these requirements from high quality animal products that are not overly processed (ex: high heat decreases protein quality in kibble). 

On a secondary note, dogs who have low energy requirements eating a commercial food that contains too much energy can result in the dog consuming less of the food at an inappropriate nutrient density. I champion homemade formulations using nutrient guidelines and high quality ingredients because the nutrient density and energy density are much easier to control.

Fiber & The Gut

Fiber decreases the digestibility of the diet. This affects not just protein, but also vitamins and minerals. However, enough fiber with the right kinds of fiber can support a healthy microbiome. The gut can ferment fiber and produce Short Chain Fatty Acids- an energy source for the gut. Enough fiber can also promote a diverse microbiome. In pig models, the gut is the primary location where sulfur-containing amino acids are metabolized.

When too much fiber, particularly insoluble fiber, is present, the digestibility of the diet decreases. This affects protein intake. Therefore, when a diet meets nutrient guidelines on paper, a high fiber diet can result in nutrient needs not being met. It can also affect the absorption of fat soluble vitamins due to 

Fermentation of some byproducts in the gut can also hinder the reabsorption of taurine. I agree with the paper very much when they say the pros and cons of fiber, as well as the level and kind, should be considered when feeding our pets.


Potassium: Potassium has been shown to be crucial for prevention of taurine deficient DCM in cats. There is less available evidence for dogs. However, many raw diets for dogs can be higher in sodium than one may think while being low in potassium. I have personally found when auditing homemade diets that potassium is low when the owner is feeding a lower percentage of body weight, but not adjusting the energy density downward (ex: Feeding 1.5% body weight in raw food but using high fat meat). Even though we don’t have solid studies to work off of, potassium should absolutely be met in the canine diet with consideration to how much sodium is in the diet. This is a strength of using nutrient guidelines when formulating homemade diets.

Choline: I was extremely happy to see choline discussed. Choline can be a trickier nutrient to understand for dogs because choline can be spared by the inclusion of other nutrients. However, the diet should not be low in choline. Choline functions by donating methyl groups (one carbon metabolism AKA methylation), but it is also important in fat digestion (pertaining to the bile)  and fat metabolism. Choline also helps regenerate methionine from homocysteine. When a diet is on the lower end of methionine and cysteine content, choline becomes more and more important for this function. A homemade, animal based diet with appropriate energy density provides high quality, abundant protein and sulfur-containing amino acids. There are some exceptions here (such as kangaroo or rabbit heavy diets).

When choline is low and homocysteine is elevated in the blood, the dogs ability to methylate homocysteine to methionine is decreased. This can have negative effects on the cardiovascular system.

The paper does discuss cholines role in the production of trimethylamine N-oxide (TMAO) in humans and cardiovascular risk. I disagree with the concrete conclusion that TMAO results in cardiovascular disease in humans as there is too much conflicting information. I will say that I do not use choline supplements (like choline bitartrate) and use the food form of choline instead because the food form of choline is more effective and results in less TMAO.

I personally think that choline is an overlooked nutrient and that raw or homemade cooked diet rich in high quality amino acids, folate, and choline (rich in eggs, some fish, and liver) appears to protect the cardiovascular system.

Methionine and Cysteine: These sulfur-containing amino acids are used to create taurine. However, as discussed, high heat and low quality sources of these amino acids can affect the synthesis of taurine. 

Taurine synthesis can vary by breed and general size of the dog (as is the case of glycine synthesis! That is a whole other topic!):

“In summary when a low, but adequate, protein diet was given to dogs of varying body size to maintain ideal body condition, a trend of lower taurine concentrations in blood, plasma, and urine was found in large dogs, but not in small dogs. Some large dogs had taurine deficiency (plasma taurine #40 mmol/L) such that, if continued for the long-term, would be at risk for development of taurine-deficiency DCM. Our results support the hypothesis that the rate of taurine synthesis in large dogs is lower than that in small dogs when taurine precursor SAA are not in excess.”  – Differences in Taurine Synthesis Rate among Dogs Relate to Differences in Their Maintenance Energy Requirement

Taurine & Carnitine (zinc, selenium, iron): Taurine is synthesized in the liver of dogs using cysteine. This process is made possible by the enzyme called “cysteine sulfinic acid decarboxylase.” The function of this enzyme will therefore directly affect taurine synthesis. The reason for low plasma taurine is not always known. The paper points out that it is speculated that a decrease in cysteine sulfinic acid decarboxylase activity and loss through bile acids may be related. 

While low taurine is identified as a risk factor relating to DCM, the cause of low plasma taurine in dogs is still unknown. The decrease may be related to genetic differences relating to enzyme function or overall dog requirements, As discussed, larger dogs may have reduced ability to synthesize taurine.

I personally choose to formulate homemade raw diets rich in high quality animal-based proteins where all amino acids are provided abundantly. When providing a cooked diet, I still meet these nutrient requirements but also add supplemental taurine (see my cooking guide here). I am not a proponent of long-term feeding of plant-based diets for dogs and am concerned about the low nutritional requirements of commercial foods- especially when they are heavily processed.

Carnitine is critical in the transport of long chain fatty acids. The heart relies heavily on these fatty acids for energy. 

Whenever the body has to synthesize something, other materials must be used. Synthesis of taurine and carnitine rely on cofactors that include iron. Iron from animal products is very bioavailable while iron from plant-based ingredients is not, This is one reason why we recommend adjusting the bioavailability settings in the RFN Sheet to use iron from animal sources, not plant sources, when meeting the RA.

Selenium and zinc are also used in the synthesis. Zinc, again, is much more available from animal products than plant products. Selenium levels in animal based products are found at more consistent levels than plant sources. Plant sources can range from having very low selenium to high selenium depending on the soil. Kidneys fed in a homemade diet would provide a consistent and reliable source of selenium. Lean red meat would provide zinc (and heme iron). Iron is also found in spleen (careful- spleen is extremely rich) and other organ meats. Zinc is also rich in eastern oysters. Zinc can often be found low in homemade raw and cooked diets frequently in my personal experience.

Thiamin: Thiamin (Vitamin B1) can be very hard to supply in a raw diet. Raw fish (such as sardines and mackerel) can reduce the thiamin content in a diet. While there is less evidence available for thiamin, low levels of thiamin causes heart conditions in several other animals, including pigs. Those feeding a homemade diet should be mindful of the thiamine content of the food they are feeding and assess whether there is thiaminase present in any of the ingredients.

Copper: Similar to Thiamin, copper deficiency studies relating to heart conditions were using other animals. Copper deficiency is relatively rare in dogs because of levels found in commercial diets. Excessive zinc supplementation (see the RFN Full Course for details) should be avoided for healthy dogs. Very often raw feeders hear that zinc is low in raw diets. This is true. However, blind supplementation should be avoided. 

Homemade diets that rely on pork, chicken, and turkey liver rather than ruminant sources of liver can often have low levels of copper in the diet. When these sources of liver are used, copper needs to be supplemented or provided from other foods (chicken heart and some oysters). I would strongly recommend a nutritional audit if you are unsure of the level of copper, or any other nutrient, in your dog’s homemade diet.

Vitamin E, Selenium, and Glutathione: While selenium was already mentioned above, Vitamin E works with selenium and glutathione to scavenge free radicals (see the antioxidant unit in the Full Course). Vitamin E is often low in homemade diets and often requires supplementation. I recommend using d-alpha with mixed tocopherols. Added tocotrienols are a bonus.

Glutathione is rich in meat and so a homemade diet rich in animal products will provide glutathione.

Selenium is more bioavailable from animal products. If selenium requirements are being rounded off using any plant products, the plant products needed to be processed to increase digestibility. Still, the form of selenium found in animal products is more bioavailable than plant products (and as mentioned, the levels vary).

Dogs with DCM can have lower levels of vitamin E and glutathione peroxidase.

OTHER FOODS

Goitrogenic Foods: Hypothyroidism has been identified as a possible risk factor. Foods heavy in broccoli, brussel sprouts, cabbage, cauliflower, and more can make hypothyroidism worse. This does not by any means mean that these foods should be avoided entirely for all dogs. Cooking these foods helps and ensuring that you are not using large amounts for any dog is important. These foods still have other benefits that can be reaped at lower levels in the diet.

Cassava: This food can increase the requirement for sulfur-amino acids. While it is commonly used in commercial diets, its use in homemade diets seems to be relatively rare. It is also not an area I have personally spent time researching.

Heavy Metals: Sourcing of food is important. Consumption of heavy metals found in food requires taurine for detoxification. Plant foods, including cereal grains, can be at higher risk for accumulating heavy metals. Geographic location of where the food is grown can also affect heavy metal content. Another point for high quality, animal based foods that are responsibly sourced! Other microminerals are also required to protect the dog from heavy metals. This is only a potential link- but in my opinion is something to keep in mind regardless of any connection with DCM.

CONCLUSION

I completely agree with the conclusion of the paper:

“DCM is a multifactorial medical condition with many proven etiologies and potential causes contributing to the development of the disease. Therefore, prospective studies investigating, not only diet, but also infection, metabolism, and genetic involvement, must be conducted. In hopes of better understanding a potential correlation with diets to DCM, more objective data need to be collected and analyzed, without sampling bias and confounding factors. While determining the cause of recently reported cases of cardiac disease is of the utmost importance, based on this review of the current literature, there is no definitive relationship these implicated diet characteristics and DCM.”

High Quality, Animal-Based, Well Formulated Fresh Food Homemade and Commercial Diets

I strongly recommend a well formulated homemade or commercial diet that uses nutrient guidelines and high quality ingredients from animal products. Well formulated is key, here. A homemade diet low in any nutrient can be detrimental. While poor formulation is a risk of using homemade diets, using nutrient requirements and understanding nutrient balance, nutrient sources and forms, and factors pertaining to breed and dog size reduces that risk dramatically. When we use the best available information regarding nutrition science and combine it with homemade diets, we get a diet that contains all the essential nutrients in their highest quality forms. We also get a diet that provides non-essential nutrients that benefit the cardiovascular system and are often not found in processed diets.

Just Because a Dog Can Synthesize Something Does Not Mean It Is Not Beneficial

I cannot say this enough. Need does not equal benefit. Vitamin C, glycine, and taurine are all considered non-essential for dogs. However, as we say, not only do numerous factors affect the dog’s ability to synthesize such nutrients, synthesizing these nutrients requires resources. The same goes for elongation of essential fatty acids from plant based sources. Preformed fatty acids (Arachidonic Acid and EPA + DHA) from (primarily) animal sources are bioavailable and require less resources for use. While larger dogs may be more affected in some of these categories (large dogs, glycine, joint issues, anyone?), it is much more ideal, generally speaking, that all dogs receive a diet from high quality ingredients that contain bioavailable nutrients. 

Well formulated fresh food diets, then, truly often provide the best forms of essential and non- essential nutrients- some of which are absent in processed diets. Fresh food diets uniquely support the whole dog in a unique way.