For more info, read Supplements for Dog Cardiovascular Health
Canine Heart Disease and the Benefits of L-Carnitine Supplementation
The two main causes of heart failure in dogs is chronic valve disease and dilated cardiomyopathy. Chronic valve disease frequently leads to congestive heart failure, affecting between 11 and 42% of dogs. In aged dogs the incidence rate is above 60%. Chronic valve disease affects primarily small to medium-sized doges, e.g., Spaniels and Dachshunds. Larger dogs, like German Shepards and Doberman pinschers, tend to suffer more from dilated cardiomyopathy (enlarged heart). Dilated cardiomyopathy is a progressive form of heart disease that develops slowly over the life of the dog, often without obvious symptoms, and can lead to the development of cardiac decompensation (inadequate circulation) and congestive heart failure later in life (6 to 10 years). Dilated cardiomyopathy is characterized by depressed systolic and diastolic pressure in the left ventricle, compensatory hypertrophy (cell size expansion), dilation of the left ventricle, and increased systemic vascular resistance. With time, as the severity of the disease increases, the left ventricle will undergo remodeling that results in a thinner, and thus weaker ventricular wall. By the time this occurs the disease is well advanced.
The symptoms of heart disease in dogs include sluggishness, despondency, weakness, unexplained weight loss, easily out of breath, a progressively worsening cough, or collapse. Any of these symptoms should trigger a visit to a veterinarian sooner rather than later, because effective treatments are available that can improve the health and prolong the life of the dog. In addition to the treatment regimen suggested by the veterinarian, supplementation with L-carnitine should also be discussed because research studies have shown positive benefits if combined with traditional treatments; L-carnitine supplementation can lower the amount and number of prescription heart medications a dog may have to take. L-carnitine supplementation may also be able to slow, arrest, or even in rare cases, partially reverse heart disease. There have also been some reports of delayed disease onset when L-carnitine supplementation is begun early in life, well before disease symptoms have appeared.
L-Carnitine is Essential to Proper Cardiac and Skeletal Muscle Function
The amino acid L-carnitine is normally synthesized in the liver of healthy animals by an enzymatic process that relies on the essential amino acids lysine and methionine. Once synthesized, the blood supply carries L-carnitine to cells and tissues throughout the body where it assists in the breakdown of fatty acids for energy. L-carnitine performs this function by binding to the surface of an intracellular organelle called mitochondria, the primary energy producing factories in our bodies. Once L-carnitine binds to this membrane it assists in the transport of fatty acids across the membrane where it is oxidized (broken down) by oxygen to produce energy.
The primary consumers of L-carnitine at the cellular level are the skeletal and cardiac muscles, and between 95 and 98% of the body’s L-carnitine is stored in these muscles. Muscle cells are also packed with mitochondria if the animal doesn’t live a sedentary lifestyle. A breakdown at any point in this cycle, whether diet or disease related, will cause rapid fatigue when muscles are exerted because the mitochondria in the muscles are forced to switch from the more efficient aerobic metabolic cycle that depends on fatty acids and oxygen, to an anaerobic metabolic cycle that depends primarily on glucose. In the presence of low L-carnitine concentrations muscle cells will be unable to keep up with demand, resulting in weakness and fatigue. For this reason, L-carnitine supplementation can provide a natural, non-prescription, and non-toxic buffer against rapid cardiac muscle fatigue.
A prominent hypothesis that was put forward years ago argues that heart disease progression occurs in part because the fatty acid metabolic cycle is dysfunctional. This was observed repeatedly in patients with severe heart disease, but more recent studies have shown that fatty acid metabolism in moderately and less severe heart disease patients is actually normal by all known measurements. Fatty acid metabolic dysfunction is therefore unlikely to be a causative factor for heart disease. Recent studies are beginning to show that metabolic dysfunction in heart disease patients is much more complex than previously thought and there may be still undiscovered pathways and molecules that could help explain disease onset and progression. L-carnitine supplementation may therefore be an effective treatment for canine heart disease because it ensures heart muscles have access to sufficient energy despite the presence of disease.
The needed dosage for prevention is 100-200 mg twice per day. To help reverse heart problems, the recommended dosage is close 1000-2000 mg twice per day.
L-Carnitine Supplementation and Adolescent Dogs
Under normal circumstances a healthy liver and diet are sufficient to maintain the fatty acid cycle properly. Red meat is an excellent source of L-carnitine, providing anywhere from 500 to 2000 mg of L-carnitine per kg. By comparison, vegetables contain only trace amounts of this amino acid. A diet poor in L-carnitine isn’t really a concern in healthy animals though, because the liver can produce enough to sustain normal function if the diet contains sufficient amounts of the amino acids lysine and methionine.
There may be an exception to the above statement when considering developing pups. Newborn pups rapidly ramp up their fatty acid metabolic cycle to near adult levels within 24 hours, and this is maintained during the suckling period. Once weaned, the L-carnitine levels fall well below the levels needed for full use of the fatty acid metabolic cycle and remain low until adulthood. By comparison, the liver and blood of adult dogs contains enough L-carnitine to fully activate the fatty acid metabolic cycle several times over. Supplementing the diet of weaned, adolescent dogs with L-carnitine may therefore provide an edge if the diet isn’t already rich in meat. Whether or not to supplement the diet of adolescent dogs with L-carnitine, and an appropriate dosage, is a decision that should be arrived at through discussions with a trusted veterinarian.
L-Carnitine Supplementation and Cognitive Decline
As we age we may experience a decline in cognitive abilities. Dogs are no exception. The decline could be the result of brain pathology, circulatory problems (heart disease), or just plain getting old. Current theories suggest cognitive decline due to normal aging may be related to decreased mitochondrial function. Since mitochondria depend so heavily on L-carnitine to produce energy, a reasonable expectation would be that diet supplementation may slow cognitive decline in aged dogs by providing metabolic support for mitochondria in the brain. When the diet of aged dogs was supplemented with α–lipoic acid and L-carnitine for several months, significant improvements in cognitive function were observed.
The research studies reviewed here are consistent with what is known about diet requirements for dogs. A diet rich in meat provides sufficient L-carnitine for healthy dogs, and this may be especially important for adolescent dogs. If the quality of the diet is in question, L-carnitine supplementation may help forestall or slow the onset of heart disease and maintain healthy muscle function. In dogs with heart disease, L-carnitine supplementation may provide some relief from the symptoms of disease and lower the amount of medications that are required. In older dogs L-carnitine supplementation may help improve cognitive abilities. The dosage that is decided upon will depend on the quality of the diet, the dog’s state of health, and discussions with a trusted veterinarian.