Whether dogs need taurine in their food is a question that has been asked a lot in these past months. The question arises following some research showing the onset of cardiac problems (specifically, diet-associated dilated cardiomyopathy) as a result of diets containing less than ideal amounts of taurine. So how important is taurine for dogs? Veterinarian Dr. Ivana Crnec provides information about taurine and its role in a dog's health.
Do Dogs Need Taurine?
First of all, what is taurine? Taurine is a unique type of amino acid. Particularly found in meat, it is also known as beta-amino sulfonic acid. Unlike most amino acids, instead of being incorporated into proteins, the taurine is found free both in body tissues (brains, eyes (retinas), muscles, heart, liver) and circulating in the blood.
Taurine can be naturally found in muscle meat, fish, shellfish, eggs, milk and cheese. Ground grown plants like corn, potatoes, wheat, rice, legumes and peas do not contain taurine.
Most animals are capable of producing taurine endogenously or in their bodies by using two precursors – the amino acids methionine and cysteine. Therefore, it can be assumed that although animals have a physiological need for taurine, most animals do not have a dietary need for taurine. However, there is an exception and that exception is the cat.
Cats always have a dietary need for taurine. If cats do not get enough taurine from their food, they are at extremely high risk of developing a specific heart condition known as dilated cardiomyopathy (DCM).
As it should always be accented, cats are not small dogs. Cats and dogs are different species with different physiologies and different requirements. This is particularly true when it comes to taurine.
Nevertheless, taurine-deficiency dilated cardiomyopathy DCM can develop in dogs, which triggers the question – how is this possible? Well, the answer is quite complex because the synthesis and utilization of taurine can be affected by many factors.
The Role of Taurine in a Dog's Diet
Taurine has two major roles in the body: it promotes normal heart function by strengthening the heart muscle and preventing arrhythmia, and they help in fat digestion considering that it's a component of the bile acids.
On top of this, taurine promotes reproductive health, promotes neurological development and health (through supporting the central nervous system and balancing the brain’s neurotransmitters), reduces seizure symptoms, regulates the levels of water and minerals, fights obesity, binds free radicals, regulates the immune system, prevents muscle degeneration and promotes healthy vascular function.
Dogs are capable of producing their own taurine from sulfur containing amino acids like methionine and cysteine. More accurately, in the presence of vitamin B6, the methionine is transformed into cysteine and then the cysteine is needed for producing taurine. Therefore, any weak link in the methionine-cysteine-taurine chain, can easily lead to taurine deficiency.
In the liver, the taurine links with bile acids to form bile salts. During digestion, the bile salts are secreted into the small intestines where they aid the fat digestion. Once food is digested, theoretically, the bile acids should be eliminated with the feces.
However, animals have developed an efficient taurine-preservation method – they reabsorb the bile salts back (enterohepatic reutilization) thus preventing the daily taurine loss in the feces. If the re-absorption is impaired or inhibited in any way more, taurine will be lost through the feces and the chances of developing taurine deficiency are higher.
Risk Factors for Taurine Deficiency in Dogs
The risk factors that lead to taurine deficiency can be divided in two major categories: dietary factors and breed-related factors. The most important dietary factors include:
- Type and level of dietary protein (low-protein diets containing limited amounts of taurine precursors or poor-quality proteins such as peas, lentils and legumes)
- Type and amount of dietary fiber
- Degree of heat used during food processing.
The above listed factors influence the taurine status in three ways:
- Bile acid binding – the bile salts can sometimes bind with some fibers and small protein chains (peptides) in the intestines. If linked, the bile salts cannot be reabsorbed and reused. Consequently, the daily loss of taurine in the feces increases. The requirements to replace that loss also increase.
- Increased microbial digestion – extrusion, canning and other thermal treatments can lead to formation of Maillard products (complexes of poorly digested sugars and amino acids). The Maillard complexes migrate to the large intestines and provide an environment that favors multiplication of the taurine-degrading bacteria. Once the population of taurine-degrading bacteria increases, the amount of taurine available for re-absorption and reuse decreases.
- Reduced taurine availability – animal based protein sources are rich in taurine. Sadly, taurine is not found in plant-based protein sources. However, even animal proteins can be a bad source of taurine, especially if treated with excessive heat.
Big dogs are at higher risk of developing taurine deficiency, because when compared to small dogs, they have much slower taurine production rate. Simply put, even when fed the same diet, large and giant breeds produce less taurine than small and toy breeds.
Additionally, some dog breeds have either a metabolic abnormality that impairs the taurine synthesis and utilization or naturally occurring higher taurine requirements.
Taurine Deficient Dilated Cardiomyopathy in Dogs
Few decades ago, the incidence of DCM in cats increased dramatically. A veterinary researcher at UC Davis investigated the increased incidence by examining 21 cats with DCM and he determined that they all had low blood levels of taurine. Once supplemented with dietary taurine, all 21 cats recovered.
Taurine deficient DCM is also possible in dogs. In fact, several dog breeds are predisposed to the condition. Those breeds include: American Cocker Spaniels, Golden Retrievers, Labrador Retrievers, English Setters, Newfoundlands, Saint Bernards, Great Danes, Boxers, Irish Wolfhounds and Doberman Pinschers.
Taurine Supplements for Dogs
Should taurine supplementation be used in dogs? Never take actions based on blind panic. The decision on whether or not to use dietary taurine supplements should not be taken lightly. Instead, it must be rational and evidence-based.
If you are concerned and want to prevent DCM, it is best advised to have your dog’s whole blood and plasma tested to measure the levels of methionine, cysteine and taurine. Once the results are ready, the vet should be objectively able of determining whether supplementation is needed.
All in all, when it comes to cats, taurine is an essential amino acid. On the flip side, when it comes to dogs, taurine is a non-essential amino acid. In both species, this unique amino acid performs a plethora of important functions.
The link between taurine and DCM has been known since 1997. Since then, many discoveries have been made, but there is still much place for further researching. Fortunately taurine deficiency DCM is a preventable, and in most cases, a successfully treatable condition.
About the Author
Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia.
She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.
Ivana’s research has been published in international journals, and she regularly attends international veterinary conferences.