Null Hypothesis: Animal ingredients are essential for amino acid homeostasis in dogs.
Alternative Hypothesis: Animal ingredients are not essential for amino acid homeostasis in dogs.
Homeostasis Definition: Any process that living things use to actively maintain fairly stable conditions necessary for survival.
Prospective Study: Amino Acid Concentrations and Echocardiographic Findings in Dogs Fed a Commercial Plant-Based Diet
- Sarah Cavanaugh, DVM, MS, DACVIM, Board Certified Cardiologist at Ross University School of Veterinary Medicine; Ryan Cavanaugh, DVM, DACVS-SA, ACVS Founding Fellow, Surgical Oncology at Ross University School of Veterinary Medicine; GE Gilbert; E Leavitt; Jennifer Ketzis, BS, MS, PHD, Associate Professor of Parasitology at Ross University School of Veterinary Medicine; Aline Vieira, DVM, MSC, PHD, Assistant Professor of Veterinary Physiology at Ross University School of Veterinary Medicine
- The proposal for this study was set in January 2018, before the Food and Drug Administration’s (FDA) announcement in July of the same year
- 38 client-owned healthy adult dogs were enrolled
- 34 dogs were transitioned to a commercial plant-based diet from their regular diets. Their regular diets include one or more animal ingredients, was commercially-available, was non-prescription, and was not grain-free
- 4 dogs remained on their regular diet, which were similar to the diets described previously
- Amino acid analysis (including plasma and whole blood taurine levels) was performed in all dogs
- Echocardiography was performed in 37 dogs at baseline
- Taurine is an amino acid
- Amino acids are found in animal-based protein sources and plant sources like soy at varying amounts, depending on the type of meat or plant
- Taurine deficiency can lead to heart disease in humans, cats and dogs
- At this time, taurine is not considered an essential, food-sourced amino acid for dogs. Taurine is synthesized in the liver from the amino acids cysteine and methionine, which should provide sufficient quantities of taurine to meet dogs’ metabolic needs
- Taurine can still be and is present in dog food. However, a pet food label does not need to reflect this presence or meet any minimum requirement per standards of the Association of American Feed Control Officials (AAFCO)
- Vegan diet for dogs
- Meets AAFCO standards
- Company was started in 2005
- The diet has always contained taurine and methionine. The last year the manufacturer, V-Dog, did a major reformulation was around 2007. The company maintains its food has always contained taurine in its formula since its inception in 2005
- Manufacturer provided the food’s nutrition profile, which states the food contains 0.19% taurine – on an as fed basis
- According to the pet food manufacturer, the taurine source is 100% vegan
- Ingredients: Dried Peas, Pea Protein, Brown Rice, Oatmeal, Potato Protein, Sorghum, Canola Oil (preserved with mixed tocopherols) , Natural Flavor, Suncured Alfalfa Meal, Brewers Dried Yeast, Dicalcium Phosphate, Flaxseeds, Millet, Calcium Carbonate, Lentils, Peanut Hearts, Quinoa, Sunflower Chips, Salt, Potassium Chloride, Choline Chloride, Taurine, Dried Carrots, Minerals (Ferrous Sulfate, Zinc Sulfate, Copper Sulfate, Sodium Selenite, Manganese Sulfate, Calcium Iodate), Dl-methionine, Dried Parsley, Vitamins (Vitamin E Supplement, Vitamin A Supplement, Niacin Supplement, D-calcium Pantothenate, Riboflavin Supplement, Vitamin D2 Supplement, Thiamine Mononitrate, Vitamin B12 Supplement, Pyridoxine Hydrochloride, Biotin, Folic Acid), L-Ascorbyl-2-Polyphosphate (A Source Of Vitamin C), Preserved with Citric Acid, Preserved with mixed Tocopherols, Dried Blueberries, Dried Cranberries, Dried Celery, Yucca Schidigera Extract, Dried Lettuce, L-carnitine, Dried Watercress, Dried Spinach, Rosemary Extract.
- Results suggested that dogs transitioned to the plant-based diet undergo changes to their amino acid profile
- 75% of the amino acids – including taurine – increased after 30 days on the plant-based diet
- Taurine (nmol/mL): pre-diet median – 107; post-diet median – 165
- Whole Blood Taurine: pre-diet median – 247; post-diet median – 298
- Methionine: pre-diet median – 70; post-diet median – 65
- Cystine: pre-diet median – 1; post-diet median – 2
- After 90 days on the plant-based diet, no dogs had echocardiographic evidence of left ventricular systolic dysfunction or dilated cardiomyopathy (DCM)
Alternative Hypothesis – Animal ingredients are not essential for amino acid homeostasis in dogs
Caveat: Additional studies are needed to determine whether the significant changes in amino acid concentrations observed in this study are due to normal day-to-day variation or due to differences in type, quality, and/or quantity of nutrients in plant-based diets compared to traditional diets
We have been following the U.S. Food and Drug Administration’s (FDA) investigation into the potential link between certain diets and DCM in dogs, which has sparked fervent concern nationwide among pet companion caregivers for the past year. As this has carried on, all of us have been subjected to:
- Speculation that the lack of grain in certain pet food diets is contributing to DCM without any scientific proof
- Speculation that ingredients that replace grains plus-or-minus exotic meats is the problem
- Warnings issued by the FDA based on frequency of reports they have received, that dog companion caregivers should not purchase certain brands – simply because they were mentioned ten or more times by pet companion parents or veterinarians that submitted case reports of dogs diagnosed with DCM. Remember that we’re talking about 524 reported cases from January 2014 through April 30, 2019, among the millions of pets fed in the country!
A lot of this speculation is being fueled by only a few veterinary cardiologists and veterinary nutritionists. Bear in mind, we have deliberately distinguished between these two specialties based on their lanes of research.
The DCM studies conducted by the veterinary cardiologists on this team have been weak in our opinion.
According to the researchers on the nutritional side of things, “Inclusion of exotic ingredients, such as kangaroo, alligator, fava beans, and lentils, adds another level of complexity to ensuring the diet is nutritious and healthy. Exotic ingredients have different nutritional profiles and different digestibility than typical ingredients and have the potential to affect the metabolism of other nutrients. For example, the bioavailability of taurine is different when included in a lamb-based diet, compared with a chicken-based diet, and can be affected by the amount and types of fiber in the diet.”
We do not disagree with the researchers on these points, but just stating them does not prove any causality. However, they are not actually conducting nutritional research and coming up with solutions for the right pet food formulations. In fact, the research could prove their assumptions to be incorrect.
They are also not considering food sensitivities to certain proteins, which can also cause health problems.
All in all, they are simply speculating, and alarming dog companion caregivers nationwide.
At Hemopet, we refer back to Sean Delaney, a board-certified veterinary nutritionist, who is not a part of this group of researchers. He and his team’s 2003 often cited study of taurine concluded, “The lowest whole blood concentrations were seen in dogs fed lamb or lamb meal and rice diets. Plasma methionine and cysteine concentrations were lower in dogs fed diets with animal meals or turkey, and whole grain rice, rice bran or barley.”
We also remember Ko and Fascetti’s study from 2016 about beet pulp, “Dietary beet pulp showed the most significant effect in lowering plasma and whole taurine concentrations, in part, by decreasing the protein digestibility (sulfur amino acid bioavailability), by enhancing fecal excretion of bile acids and possibly, by enhancing degradation of taurine by the gut microflora in dogs.”
We aren’t too sure about you, but our heads feel somewhat like the ping pong ball at a ping pong match!
The Cavanaugh Study
That is the beauty of Cavanaugh and her team’s study that we detailed above.
- It eliminates one of the multiple variables under debate – meat proteins
- It also eliminates the variability/bioavailability of taurine, cyst(e)ine and methionine between the various meat sources. In essence, it suggests dogs are not dependent on meat-based meals for adequate taurine supplementation if they are given the right amount of taurine supplementation, regardless of the source of taurine.
- The study also suggests that peas are not inhibiting the absorption of taurine. However, we do not know if peas inhibit cyst(e)ine and methionine. Additionally, we do not know if peas are inhibiting the meat proteins from supplying the adequate amount of taurine, cyst(e)ine and methionine
It would have been interesting if the food used was supplemented with methionine and cyst(e)ine instead of taurine. This would give us better insight into whether dogs are efficiently synthesizing these two amino acids in the gut to make taurine.
The Hemopet Dodds Study
A study of 523 Golden Retrievers without evidence of canine heart disease or DCM and fed a variety if diet types was just published (Dodds, 2019). This study examined the source of food sensitivities and intolerances in a retrospective cohort of predominantly adult (98% of 523) Golden Retrievers (GR), generally healthy except for the presence of ongoing pruritus and/or gastrointestinal (GI) problems. Electronic data files of GR from January 2016 through December2018 were analyzed. The dogs were divided into 4 subgroups according to diet type: commercial grain-containing kibbles (n =273; 52%); commercial or home-prepared raw diets without wheat, corn, or soy (n =133; 25%); commercial grain-free (n =79; 15%); or home-prepared cooked diets without wheat, corn, or soy (n =38;7%). Within the 4 diet subgroups, 24 ingredients were tested and ranked for food reactivities based upon the test results. Of the 24 ingredients tested, turkey and white-colored fish were the most reactive (54–60%), followed by venison and corn, including cornstarch (44–48%). The lowest reactive foods were lamb and those that caused no reaction (11%). It was concluded that among generally healthy, adult GR, the ranking of 24 identified reactive food ingredients was the same across the 4 diet subgroups, indicating that diet type is not the determining factor for food sensitivities or intolerances in GR.
Whole blood or plasma taurine concentrations were measured in a subset of dogs (n=22) fed grain-free diets. The results were normal or modestly elevated.
After reading these studies, many of our minds – and probably yours, too – are churning with new questions, personal conclusions and even speculation. As we have stated in the past, we are not going to toss out our thoughts or current data.
We do think that further research needs to be conducted into diet combinations and the bioavailability of taurine from all food ingredients.
Canine Dilated Cardiomyopathy Archives. Hemopet, https://www.hemopet.org/tag/canine-dilated-cardiomyopathy.
Cavanaugh, SM, et al. “Amino Acid Concentrations and Echocardiographic Findings in Dogs Fed a Commercial Plant-Based Diet.” Ross University School of Veterinary Medicine, 2019.
Delaney, SJ, et al. “Plasma and Whole Blood Taurine in Normal Dogs of Varying Size Fed Commercially Prepared Food.” Journal of Animal Physiology and Animal Nutrition, vol. 87, no. 5-6, June 2003, pp. 236–244., http://www.ncbi.nlm.nih.gov/pubmed/12752830.
Dodds, WJ. “Food Sensitivity and Intolerances Associated with Diet Type in Golden Retrievers: A Retrospective Study.” Journal of the American Holistic Veterinary Medical Association, vol 56, Fall, 2019, pp.52-57.
“FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.” U.S. Food and Drug Administration, 27 June 2019, http://www.fda.gov/animal-veterinary/news-events/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy.
Freeman, LM, et al. “Diet-Associated Dilated Cardiomyopathy in Dogs: What Do We Know?” Journal of the American Veterinary Medical Association, vol. 253, no. 11, 1 Dec. 2018, pp.1390–1394., doi:10.2460/javma.253.11.1390. https://avmajournals.avma.org/doi/abs/10.2460/javma.253.11.1390.
Ko, KS, and Fascetti, A. “Dietary Beet Pulp Decreases Taurine Status in Dogs Fed Low Protein Diet.” Journal of Animal Science and Technology, vol. 58, Aug. 2016, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4971673.