This is a lot of info but please bear with me and take the time to read it as there is a lot of misinformation out there regarding grain free diets.

 

When selecting a diet for your dog, I recommend: 

• High protein foods where the first three ingredients, or at least the first, is real meat 

• Avoid peas, lentils, chickpeas or other legumes in the first five ingredients (ideally entirely)

• Avoid fillers like corn, which has a high glycemic index; in large amounts, high starch diets may reduce protein digestibility and contribute to blood sugar spikes 

• Commercial grain inclusive diets often use large amounts of corn or other high starch ingredients, which can increase glycemic load and reduce protein digestibility, potentially limiting amino acids needed for taurine synthesis. 

• Ensure adequate fat, fiber and balanced nutrients, including taurine, especially if feeding grain free 

• Rotate flavors and formulas carefully, focusing on ingredients rather than marketing claims 

• Information about raw feeding additives , nutrition and diet and supplements can be found here

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Why this matters: Dogs are facultative carnivores, they thrive on meat based diets and do not require grains. Avoiding legumes and fillers helps maximize nutrient absorption, supports healthy digestion and reduces potential risks associated with diet related cardiac concerns. 

The detailed information and citations below are provided for dog owners who wish to read the science for themselves and understand how these conclusions were reached and why I choose to feed high protein grain free diets to my dogs. 

Grain Free Diets, DCM and What the Science Actually Shows 

Dogs are facultative carnivores, meaning they are biologically adapted to thrive primarily on animal based nutrition, but they can also digest and utilize certain plant ingredients. This flexibility allows for a wide range of diet formulations to meet nutritional needs, when those diets are properly balanced and well formulated. 
In recent years, grain free diets have been widely criticized due to concerns about a possible link to dilated cardiomyopathy (DCM). Much of this concern traces back to reports collected by the U.S. Food and Drug Administration (FDA). However, it’s important to understand that the FDA investigation was NOT A CONTROLLED CLINICAL TRIAL. It was based on observational case reports, meaning veterinarians voluntarily reported cases they observed in practice. These reports can identify patterns worth studying, but they CANNOT ESTABLISH CAUSE AND EFFECT. 

To date, the ONLY LONG TERM CONTROLLED FEEDING STUDY directly comparing grain free and grain inclusive diets in healthy dogs found NO CLINICALLY SIGNIFICANT DIFFERENCES IN HEART HEALTH or taurine levels between diet groups over an 18 month period. All dogs in the study remained clinically normal with respect to DCM. 
In other words: 

• Grain free diets themselves have not been proven to cause DCM 

• The FDA data most often cited were not controlled studies 

• Controlled research to date has not demonstrated harm from grain free diets when properly formulated​

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The study everyone refers to claiming that grain free causes heart problems: 

• FDA Case Report Data (2018–2019) 
  Between January 1, 2014 and November 30, 2018, the U.S. Food and Drug Administration (FDA) received 325 reports of canine dilated cardiomyopathy (DCM) diagnoses that were voluntarily submitted by veterinarians or pet owners. Of these, ONLY 104 dogs with detailed records showed characteristic heart changes on cardiac ultrasound consistent with DCM and NOT ALL DOGS UNDERWENT COMPLETE DIAGNOSTIC WORKUPS, CONTROLLED FOLLOW UP OR STANDARDIZED TREATMENT. ​

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Of those dogs, 119 (about 21%) died during the reporting period, since this was a voluntary study, they DO NOT DISTINGUISH CAUSE OF DEATH. Some reported dogs were euthanized for other quality‑of‑life reasons rather than progressive DCM. 

In a subset of 196 reports where the dog was reported to be fed a single primary diet, approximately 90 % of the diets were labeled “grain‑free.” However, these data represent voluntary case reports, not a controlled scientific study with defined sampling criteria or randomization.  

Additionally, analysis of reported breeds showed that a large proportion (about 73 %) of these cases were in breeds already genetically predisposed to DCM (e.g., Golden Retrievers, Doberman Pinschers, Boxers), which complicates assumptions that diet alone was responsible.  

Importantly, the FDA states that reported numbers alone do not establish a causal relationship between pet food and DCM, and the agency continues to support further research. 
 
What started the concern 

In 2018, the U.S. Food and Drug Administration (FDA) announced it was investigating a possible association between certain diets and canine dilated cardiomyopathy (DCM), a disease in which the heart becomes enlarged and weakened. Many reported cases involved foods labeled “grain-free,” which quickly led to widespread concern. 

From the FDA’s June 27, 2019 update: 

“More than 90 percent of the reported products were ‘grain-free,’ and 93 percent of reported products had peas and/or lentils… Animal protein sources in the reported diets varied widely.” 

Source (FDA Vet-LIRN Report): 
https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy 

However, the FDA also made an important clarification: 
“Adverse event numbers alone do not provide sufficient data to establish a causal relationship with reported product(s).” 

Source (FDA Update, December 23, 2022): 
https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy 

Key point: The FDA reports identified an ASSOCIATION, NOT PROOF OF CAUSATION. 

Between January 1, 2014 and April 30, 2019, the U.S. Food and Drug Administration (FDA) received reports of 560 dogs diagnosed with dilated cardiomyopathy (DCM) associated with dietary histories submitted by veterinarians or owners. Of those dogs, 119 (about 21%) died during the reporting period, since this was a voluntary study, they DO NOT DISTINGUISH CAUSE OF DEATH. Some reported dogs were euthanized for quality‑of‑life reasons rather than progressive DCM.  Additionally, FDA’s Vet‑LIRN performed necropsies on a subset of cases, including dogs that died or were euthanized, and coordinated further histopathology to investigate underlying lesions and potential causes. These data represent VOLUNTARY CASE REPORTS, NOT A CONTROLLED CLINICAL STUDY, and the agency continues to emphasize that reported numbers alone do not establish a causal relationship between diet and disease.  

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• This mortality data comes from case reports, which are not a controlled cohort or randomized trial. They are submitted voluntarily and reflect cases that veterinarians or owners chose to report to the FDA.  

• The reports include variable clinical data, and NOT ALL DOGS UNDERWENT COMPLETE DIAGNOSTIC WORKUPS, CONTROLLED FOLLOW‑UP, OR STANDARDIZED TREATMENT.  

• Because of this, the data cannot establish causality between diet and DCM, which is why the FDA continues to say that the numbers alone do not prove any specific diet causes DCM. 

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What the reported diets actually had in common 

The diets reported in DCM cases were not simply “grain-free.” Many shared these characteristics: 

• High inclusion of peas, lentils, chickpeas, or other legumes 

• Use of pulses or potatoes as major carbohydrate sources 

• Highly processed formulations 

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Source (FDA Case Analysis): 
https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy 

Importantly, the FDA’s own nutrient analysis found: 

“Average percent protein, fat, total taurine, total cystine, total methionine, and total methionine-cystine were similar for both grain-free labeled and grain-containing products.” 

Source (FDA Vet-LIRN Nutrient Analysis, February 2019): 
https://www.fda.gov/animal-veterinary/science-research/vet-lirn-update-investigation-dilated-cardiomyopathy-february-2019 

This means grain free diets were not nutritionally deficient by default, and nutrient levels overlapped heavily with grain inclusive diets. 

Taurine deficiency: part of the discussion, not the entire cause 

Taurine is an amino acid dogs typically synthesize from methionine and cystine. Early concern focused on taurine deficiency as a cause of diet-associated DCM. 

However: 

• Many diets involved in reported cases met recommended levels of taurine precursors. 

• Not all dogs diagnosed with DCM were taurine deficient. ​

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A large retrospective clinical study found that: 
Taurine supplementation was not independently associated with survival when analyzed alongside other variables. 

Source (Peer-reviewed retrospective study): 
https://pmc.ncbi.nlm.nih.gov/articles/PMC7848368/ 

This indicates that while taurine deficiency may play a role in some cases, it does not fully explain diet associated DCM. 

Peas, Legumes, and Taurine Metabolism

 
Some veterinarians and researchers have also discussed the role of ingredients like peas, lentils, and other legumes in grain free diets. Peas and similar pulse ingredients tend to be lower in certain sulfur containing amino acids (such as methionine), which dogs use to synthesize taurine, and they are relatively high in soluble fiber. 

Soluble fiber can bind bile acids in the digestive tract. Because bile acids are synthesized from taurine, increased bile acid loss through feces may raise the body’s demand for taurine and influence how taurine is metabolized and recycled. While this does not prove that peas “block taurine absorption,” it provides a biologically plausible explanation for why some legume-heavy diets have been examined in relation to taurine status and DCM. 

It is important to emphasize that this mechanism remains theoretical, and current research does not demonstrate that peas or legumes directly cause dilated cardiomyopathy. Controlled feeding studies that included grain free diets with legume ingredients have not found clinically significant differences in cardiac health when compared with grain inclusive diets in healthy dogs. 
 

Review of dietary fiber, bile acids, and taurine metabolism: 
https://academic.oup.com/jas/advance-article/doi/10.1093/jas/skaf225/8196486 
Retrospective DCM and taurine analysis: 
https://pmc.ncbi.nlm.nih.gov/articles/PMC7848368/ 
Controlled feeding study (grain-free vs grain-inclusive diets): 
https://pmc.ncbi.nlm.nih.gov/articles/PMC7007769/ 
 
Diet Composition Matters More Than Grain Free Labels 

The diets in question were not just grain free, they were legume heavy or used other carbohydrate sources. Research shows: 

• Average protein, fat, taurine and amino acid levels were often similar between grain free and grain inclusive diets 

• Taurine supplementation or adequate protein typically prevents taurine deficiency even on grain free diets 

• Protein quality, digestibility and amino acid balance are far more important than the presence of grains 

 
Taurine and High Metabolism Sporting Dogs 
For breeds with high metabolic demand or those prone to taurine issues, diet formulation is critical: 

• Dogs can synthesize taurine from methionine and cystine, but diet composition affects how efficiently this occurs 

• Diets with high quality animal proteins and sufficient fat and fiber help maintain taurine and overall nutrient balance 

• Commercial grain inclusive diets often rely on corn or other high starch ingredients, which can: 

• Raise glycemic load 

• Potentially reduce protein digestibility, which can affect the bioavailability of amino acids important for taurine synthesis 

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What controlled and peer-reviewed studies show 

Controlled feeding study (18 months) 

In a long term controlled feeding study of healthy adult dogs fed grain-free and grain-inclusive diets (with and without peas or potatoes), researchers found: 
“No clinically significant changes or between group differences… Whole blood and plasma taurine concentrations remained within reference ranges… all dogs were clinically normal with respect to DCM.” 
 

Source (PubMed, controlled feeding trial): 
https://pubmed.ncbi.nlm.nih.gov/40642821/ 

This is one of the strongest controlled studies available and did not find that grain free diets caused DCM in healthy dogs. 

 

Retrospective clinical studies 

Other studies reviewing dogs diagnosed with DCM found mixed results: 

• Some dogs improved after diet changes and/or taurine supplementation. 

• Improvement was not consistent across all cases. 

• Taurine status alone did not predict outcomes in all dogs. ​

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Source (Clinical outcome study): 
https://pubmed.ncbi.nlm.nih.gov/33741312/ 
These findings suggest diet may be one contributing factor among many, not a single direct cause. 
 
The FDA’s final position 
After several years of investigation, the FDA concluded: 
“The association between diet and DCM in dogs is a complex scientific issue that may involve multiple factors… FDA is unable to establish a causal relationship.” 

Source (FDA Final Updates): 
https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy 
 

 

Summary for Puppy Owners and Buyers 

✔ Grain-free diets have not been proven to cause DCM 
No controlled study has demonstrated a direct causal link between grain-free diets and dilated cardiomyopathy. 
✔ Most reported cases involved non traditional formulations 
High inclusion of legumes and pulses, not simply the absence of grains, is the common thread in many reported cases. 
✔ Taurine deficiency is not universal 
Many dogs with DCM have normal taurine levels, and taurine supplementation does not guarantee resolution. 
✔ Diet quality and formulation matter more than “grain-free” labels 
Balanced amino acids, digestibility, bioavailability and appropriate protein sources are likely more important than whether a diet contains corn, rice, or other grains. 
 
Breeder Feeding Philosophy & Diet Information Disclaimer 

As a breeder, I am frequently asked for guidance on feeding puppies and adult dogs. While I am not a veterinarian, I do have years of hands on experience raising, conditioning and maintaining active, high metabolism dogs and I stay current with available research on canine nutrition. 
The feeding recommendations I share are not medical advice, but rather evidence based suggestions and personal experience with diets and brands that I believe perform well in real world conditions. Ultimately, every dog is an individual, and owners should always work with their veterinarian when making medical or dietary decisions for their dogs.