Nutrition plays a key role in
DCM is a condition that prevents the heart from pumping blood around effectively. The muscle wall becomes thinner as a result of degeneration of the heart muscle. The pressure in the heart reinforces this process; the heart grows steadily in size, but loses strength at the same time. This condition develops slowly but progressively and may lead to heart failure and subsequently (usually) death. The exact cause is not known as yet, which makes effective treatment difficult. It is becoming increasingly clear, however, that nutrition and certain amino acids play a key role.
[Written by: M. van de Beek-Weij, MSc.]
A variety of factors have been linked to DCM, such as diet, infections and genetics. This condition is more common in larger dog breeds and males have a slightly higher risk than females. According to the US FDA data below, small dog breeds rarely develop DCM.
Research has shown links between DCM and taurine and/or carnitine deficiencies. These occur in, for example, diets in which amino acids are insufficiently available, such as lamb/rice-based diets.
Nutrition is an important aspect when treating this condition. In the past, sodium restriction was the most common nutritional advice for dogs with DCM because little additional knowledge was available. Today, we know more.
Most amino acids are needed for protein building. This does not apply to taurine, which occurs freely in the body and is found in its highest concentrations in the heart muscle, the muscles, the central nervous system and platelets. Taurine is not considered an essential amino acid for dogs. It does have many functions, however, and is, among other things, necessary for the heart muscle to function normally.
Although its exact functioning is not clear, taurine appears to regulate the concentration and bioavailability of calcium in heart cells. What's more, this amino acid acts as an antioxidant and neutralises free radicals, thus protecting the heart from cellular osmolarity.
Other plausible functions include N-methylation of cell membrane phospholipids, effects on contractile proteins, and interactions with the renin-angiotensin-aldosterone system (RAAS).
The relationship between taurine and DCM has been investigated in several studies. In dogs, a taurine-free diet
does not lead to taurine depletion, which does happen in cats. Administering additional taurine to cocker spaniels with DCM nevertheless showed a significant echocardiographic improvement compared with the control group. Another study found that dogs that were fed a long-term protein-restricted diet due to bladder stones issues developed DCM. Supplementation with additional taurine/carnitine extended their lifespan and resulted in recovery in 3 out of 8 dogs. Research into low-protein diets in healthy dogs over a 48-month period showed a significant reduction in taurine levels in the blood. One dog developed DCM and recovered almost entirely after administration of additional taurine.
Taurine deficiency has also been identified in dogs that were fed a diet of tofu (soy) with sufficient protein. Ditto for diets with rice and lamb.
Soy and lamb/rice-based diets are low in sulphate-containing amino acids, and soy also contains less taurine than meat proteins. The deficiency recovered when the diet was changed or when additional methionine or taurine was added. In a comparative study in dogs that were fed diets of rice/lamb or poultry meal, taurine was only found in the urine of dogs from the second group. After enriching the diet with methionine, taurine in the urine was also measured in the lamb/rice group.
L-carnitine is a small, water-soluble molecule that dogs obtain from dietary proteins. It can also be formed in the liver from lysine and methionine. Iron, vitamin C and vitamin B6 are also required for this synthesis. Since the amino group of carnitine is not free, it cannot be used in protein synthesis. High levels of L-carnitine are found in the heart and muscles. Carnitine is an important component of enzymes in the membranes of mitochondria. These enzymes transport fatty acids that supply the (heart) muscle with energy. Carnitine also buffers the acyl-CoA/CoA ratio, which is important for oxidative reactions in the mitochondria. In a litter of Boxers and both parents, DCM
was established. After administration of additional carnitine, an increased shortening fraction was observed in two pups, indicating the volume of blood in the heart before the heart contracts. Unfortunately, the dosage of carnitine came too late for the parent animals. The combined
provision of additional taurine and carnitine to cocker spaniels with DCM who were fed protein-poor diets for bladder stones showed a significant improvement in heart function and survival rates.
Treating dogs with DCM with a modified diet looks promising. Two dietary supplements that have been shown to have positive effects are taurine and carnitine. In some dogs, a significant improvement in heart function has even been observed when these additives were used in the diet.